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Climate Change and Global Warming

Climate Change and Global Warming

RECENT DEVELOPMENTS

Surface Temperature Reconstructions for the Last 2000 Years (NAS report) was published in 2006 (and can be read for free online) and was prepared for the Committee on Science, US House of Representatives by the National Acedemies of Science: "to summarize current scientific information on the temperature record for the past two millennia, describe the main areas of uncertainty and how significant they are, describe the principal methodologies used and any problems with these approaches, and explain how central is the debate over the paleoclimate temperature record to the state of scientific knowledge on global climate change". A major factor which contributed to this report being written was the 'Hockey Stick' global temperature reconstruction created by Mann, Bradley & Hughes 1999 which is discussed in weakness 2 below. The main conclusions of the report were:
1) It can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries.
2) Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified.
3) Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.
4) Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.

So the NAS report broadly supports the claims that current global temperatures may be the highest in the last millennium but says the claims that the 1990s and 1998 were the warmest decade and year respectively are unjustified on statistical grounds. And the report concluded that there is clear evidence of both a Medieval Warm Period (MWP) and a Little Ice Age (LIA) which were largely absent from Mann et al (1999) 'Hockey Stick' reconstruction.

Global Temperature Change is a paper published in September 2006 which is even more controversial than the Mann et al 1999 paper as it says "Comparison of measured sea surface temperatures in the Western Pacific with paleoclimate data suggests that this critical ocean region, and probably the planet as a whole, is approximately as warm now as at the Holocene maximum and within 1°C of the maximum temperature of the past million years." To suggest that current global temperatures are approximately as warm now as at the Holocene maximum is not credible when you consider we know Milkanovitch cycles provide a warming forcing (see Astronomical Theory of Climate Change). So from about 5000 to 9000 years ago during the early to mid-Holocene, astronomical forcings favoured higher global temperatures and this is reflected in higher temperatures in many regions around the world: ice cores in the Antarctic show warmer temperatures between 6 & 10 ka y BP (Evidence for an early Holocene climatic optimum in the Antarctic deep ice-core record); ice cores from tropical glaciers in Peru show maximum Holocene warmth to have occured 5200 to 8400 BP (Late Glacial Stage and Holocene Tropical Ice Core Records from Huascarán, Peru); in Europe, the mid-Holocene warming was apparently confined to northern parts with southern parts cooling and central parts no change (The temperature of Europe during the Holocene reconstructed from pollen data); in China, Temperature estimates for the Holocene optimum were 1 °C to 6 °C higher than today,depending on the geographical location (Paleoenvironments in China during the Last Glacial Maximum and the Holocene Optimum); and the Arctic and Siberia also saw anomalous warming with much reduced arctic sea ice which meant warmer conditions all year round which allowed the Siberian tree line to advance northwards to what today is the arctic coastline (Holocene Treeline History and Climate Change Across Northern Eurasia). A more comprehensive list of papers documenting warmth in the Holocene maximum can be found on UKWeatherWorld. In these cases, these widespread regional warmings are of the order of several degrees C compared with today which logically means the average global temperature was higher than today for several thousand years in the early to mid-Holocene. To argue that current global temperatures are approximately the same as the Holocene maximum is not a credible argument. And the paper did not attempt to average all the regional proxies but claimed western equatorial Pacific Sea Surface Temperatures were probably representative of the globe. There is a pattern here. Mann et al (1999) tried to eradicate the MWP & LIA from the climate history of the last millennium but failed and now other climate scientists are attempting to delete the Holocene maximum from the Holocene. The Hansen paper is a clear demand for greater action on curbing greenhouse gas emissions and his dramatic and controversial claim that todays current temps are approximately the same as in the Holocene maximum and within 1 C of the maximum in the last million years are probably designed to achieve this.

Another recent paper of interest is Recent Cooling of the Upper Ocean which reports a 20% loss of upper ocean heat content between 2003 and 2005, which had accumulated between 1955 and 2003. This was an unexpected finding not supported by climate models although a comparitive ocean cooling event was observed in the early 1980s. The authors concluded that these findings suggest that the observed decrease in upper ocean heat content from 2003 to 2005 could be the result of a net loss of heat from the Earth to space. Given that increasing greenhouse gases are expected to inhibit this process, these ocean cooling observations are very interesting. And this paper raises questions about the accuracy and relevance of the measures of global temperature which do not show a global cooling over the period 2003 to 2005 although oceans comprise 75% of the Earth's surface. In the study, the upper ocean was defined as the upper 700m of ocean and the surface cooled much less than the ocean in the 200-700m range. Therefore the global surface temperature record which only include satellite measurements of the sea surface temperature have not captured this significant ocean cooling and loss of energy from the earth-atmosphere system. Indeed a new versiion of the NCDC measure of global temperature showed 2005 to be the warmest year on record Annual Climate of 2005.


THE IPCC view on future climate change and its consequences for mankind and the environment are very pessimistic and negative. And the message it is giving is simple: we can avoid these negative consequences if man-made emissions of carbon dioxide are drastically reduced. While it is true that the Kyoto Protocol has now been ratified, it is widely acknowledged that even if countries honour the agreement, the reduction of 5.2% in greenhouse gas emissions relative to 1990 values will only reduce global temperatures by 0.02 to 0.28 C by 2050 compared to the increase of 1.4°C to 5.8°C between 1990 and 2100 predicted by the IPCC. Far more dramatic cuts than those of the Kyoto protocol are required but rather than coming down, global and UK  emissions of carbon dioxide are rising at an increasing rate, higher demand for fossil fuels is driving prices upwards and experts  predict massive growth in fossil fuel use in the next few decades (eg world oil use is expected to grow from 78 million barrels per day in 2002 to 103 million barrels per day in 2015 and 119 million barrels per day in 2025. Source: International Energy Outlook). No reputable forecasts are anticipating a massive decrease in future fossil fuel use which could deliver the drastic reductions in man-made emissions of carbon dioxide which the IPCC say is necessary to avoid climate catastrophe. There is a great deal of optimism that renewable energy can provide a painless solution to the problem of controlling carbon dioxide emissions and over the longer term, such optimism is hopefully apt, but over the shorter term and the period of time the IPCC says we must make drastic cuts to global carbon dioxide emissions, renewables cannot meet a quarter of the UK's electricity needs never mind a significant part of the world's electricity demand. This is illustrated by the fact that after 8 years in power, the British government which says it is serious about reducing the UK's greenhouse gas emissions and tackling climate change has only managed to generate 2-3% of the UK's electricity from renewables. At this rate, we may manage 30% in 80 years time!

THEREFORE it appears unlikely that the dramatic cuts in greenhouse gas emissions being called for by the IPCC  in the next couple of decades are going to happen. What the IPCC is advising/demanding is unrealistic because fossil fuels are so essential to our way of life and bring us many great benefits. If the IPCC is right about the science of man-made climate change, significant global warming can be expected during the course of the 21st century and the consequences for man and the environment are going to be very negative. On the other hand, if the IPCC has got the science wrong, then the future may not be nearly as bleak and disastrous as some would have us believe. For these reasons, the author and other sceptics of man-made global warming feel motivated to query and challenge these very pessimistic and alarmist views on current and future climate change. To be clear, this article is not querying the need for controlling carbon dioxide emissions. But given the fact that UK and global emissions are still increasing and likely to do so for the foreseeable future, it is very relevant to scrutinize the  science of climate change and to query the very pessimistic predictions. It is in all our interests that the scientists are wrong and that the climate effects of increasing carbon dioxide are not as potent as they are arguing.

THE IPCC Third Assessment Report  says that there is new and stronger evidence that "most of the observed warming observed over the last 50 years is attributable to human activities" which is fairly certain.  Playing the Devil's Advocate is the process by which the quality of an argument can be tested and any weaknesses sought out. There is no reason why this process cannot be applied to the science of man-made climate change by those who are convinced of the science to test whether the evidence for man-made climate change is indeed as strong and robust as the IPCC claims. In the author's view, the evidence is not strong and robust and nine weaknesses in the science of climate change are identified below. In most cases, links to the references cited are available in the References section at the end.

1. The atmosphere is much more complex than a mere container for greenhouse gases
2. Paleoclimate & climate model reconstructions of temperatures over the last millennium are uncertain
3. Detection & Attribution Studies are not robust evidence of man-made climate change as claimed by scientists
4. Regional climate change is incorrectly being used as evidence of man-made climate change
5. The 300 year long Central England Temperature record shows seasonal warming which suggests that the magnitude of global warming is not large
6. Cold weather patterns appear to account for mid-20th century global cooling, not sulphate aerosols from coal burning
7. The Earth's climate is not stable
8. Evidence that the Medieval Warm Period was warmer than the 20th century exists
9. Scientists can't agree on the rate of global warming over the last few decades and how unusual is it?

1) THE ATMOSPHERE IS MUCH MORE COMPLEX THAN A MERE CONTAINER FOR GREENHOUSE GASES

THE main argument for man-made global warming is that carbon dioxide is a greenhouse gas and therefore increased amounts in the atmosphere MUST cause increased global temperature by increased greenhouse gas forcing. And a significant increase in greenhouse gas forcing from the combined effects of increasing carbon dioxide, methane, ozone & chloroflurocarbons has been measured in a study which compared data from 1970 with 1997 (Harries, Brindley, Sagoo & Bantges, 2001).  However, relating this increased greenhouse gas forcing to global temperature change isn't straightfoward as we know global temperature varies naturally owing to changes in both external forcings (solar, volcanic & greenhouse gas forcing) and from internal atmospheric variability. Nevertheless, it seems likely that increased greenhouse gas forcing has made a contribution to the observed global warming over the last 50 years but the IPCC view that it accounts for "most" global warming may be over the top. Two reasons why this may be the case are shown below:

  1. water vapour is by far the most important greenhouse gas as it absorbs infra-red radiation emitted by the Earth 's surface at a  wide range of wavelengths (article 1; article 2). At some wavelengths however, the absorption is weak or close to zero leaving several small windows. Exactly at these wavelengths, CO2, CH4 and other greenhouse gases like nitrous oxide, ozone and chlorofluorocarbons absorb and shorten the window. Articles 1 & 2 also show that there is considerable overlap in the absorption bands of these greenhouse gases which makes it very difficult to predict what the effect of increasing the atmospheric concentration of  any of these gases (eg CO2) would be. Harries et al (2001) found an increase in water vapour in the tropical trophosphere associated with the 1997-1998 El Nino to be the cause of the most dramatic change in greenhouse gas forcing from 1970 to 1997, but collectively the change from trace greenhouse gases was significant and the contributions from carbon dioxide and methane were noticeable
  2. satellite images of the earth from space show that the atmosphere contains a wide range of different weather systems from individual cumulus clouds & thunderstorms to extra-tropical cyclones & large tropical storms (typhoons, cyclones & hurricanes)
  3. indicating that the atmosphere is much more complex than a mere container for greenhouse gases. We call this complexity weather. The atmosphere plays the main role (together with the oceans) of redistribution of heat around the Earth which is strongly heated in the tropics but heated little at the poles and energy is transferred around by advection and the processes of evaporation (which consumes energy) and latent heat of vaporisation (which releases energy): the idea that energy transfers in the atmosphere are merely a balance between incoming shortwave radiation and outgoing longwave radiation (the greenhouse effect) is grossly simplistic but this argument that increased greenhouse gases MUST increase global temperatures ignores the complexity of the atmosphere and raises on a pedestal this grossly simplistic argument and exaggerates the role the greenhouse effect plays in global climate .

CLIMATE models do of course attempt to deal with all processes that occur within the earth-atmosphere system and these models consistently conclude that the rise in atmospheric levels of carbon dioxide from pre-industrial levels of 280ppm to 380ppm today MUST have led to an increase in global temperatures. So the models support the simplistic view of the atmosphere as a mere container for greenhouse gases. Why?  The radiative properties of greenhouse gases are estimated theoretically (they cannot be measured)  using simple formulae which the IPCC change from time to time due to large uncertainties. Using the new formulae, the radiative forcing due to the increases in the well-mixed greenhouse gases from the pre-industrial (1750) to present time (1998) is now estimated to be +2.43 Wm-2 (comprising CO2 (1.46 Wm-2), CH4 (0.48 Wm-2), N2O (0.15 Wm-2) and halocarbons (halogen-containing compounds) (0.34 Wm-2)), with an uncertainty of 10% (Chapter 6: Radiative Forcing of Climate Change). The IPPC Report,  Climate Change 2001: The scientific basis discusses the radiative forcing of a doubling of CO2 and how the "new best estimate" (their words) is 3.7 W m-2 which is 15% lower than the best estimate in 1996. These figures for the radiative forcing of different greenhouse gases are then added to climate models as variables and the model predictions clearly show that these figures have a large influence by showing a linear relationship between atmospheric levels of carbon dioxide and global temperatures. Now if the models are perfect, then there really is a simple linear relationship between atmospheric levels of carbon dioxide and global temperatures but of course the models are not perfect but are scientists' best attempt to simulate the earth-atmosphere system. There is no long history of such modelling of the Earth's climate and our understanding of the climate is poor which the IPCC admitted in 2001. The last sentence of the Executive Summary of the last chapter (Chapter 14) states "The challenges to understanding the Earth system, including the human component, are daunting, but these challenges simply must be met" which shows that the IPCC is humble enough to admit it does not fully understand the Earth-climate system. It is certain that climate models are far from perfect and it is quite reasonable to be sceptical about their black & white conclusions that recent global warming owes to increasing greenhouse gases.

IMPLICATION: given that there is a paper (Harries et al, 2001) which shows that increasing greenhouse gases have increased greenhouse gas forcing, it is logical to accept that this has made a contribution to the rise in global temperatures over the last 50 years. But the atmosphere is much more complex than merely a container for greenhouse gases and the role of internal climate variability generated by the complexity of the atmosphere is not well-understood and may possibly account for much of the global warming observed over the last 50 years. The IPCC view of "most" global warming over the last 50 years owing to greenhouse gases may be over the top.


2) PALEOCLIMATE  & CLIMATE MODEL RECONSTRUCTIONS OF TEMPERATURES OVER THE LAST MILLENNIUM ARE UNCERTAIN

PALEOCLIMATOLOGY has become a huge topic of research over the last decade probably because proxies for temperature are one of  just two methodologies (the other being climate models) which enable scientists to construct a temperature history for the globe prior to thermometer records which only go back to 1860. These paleoclimate studies provide data on the magnitude of natural climate variability which have implications for the identification of man-made global warming in temperature records and implications for predictions of future climate.

CLIMATE over the Past Millennia (Jones & Mann, 2004) is a good review of the different paleoclimate data used as proxies for temperature and the crucial issue is that factors other than temperature affect the biological, chemical or physical properties of the proxy which are taken to represent temperature. For example, tree ring and tree ring density data are the most widely used proxies and other factors such as rainfall, soil fertility and rising carbon dioxide levels may also affect tree ring width and density, thereby confounding the relationship between tree ring data and temperature. This means paleoclimate proxies are always inferior to thermometers readings as measures of temperature and have large uncertainties associated with them. Arguably these uncertainties are being forgotten in the man-made climate change debate and the paleoclimate reconstructions are being taken far too seriously by scientists.

THE paleoclimate reconstruction which has caused the most hullabaloo is that of Mann, Bradley & Hughes (1998) which commenced in 1400 AD and this was extended back to 1000 AD in Mann, Bradley & Hughes (1999).  This reconstruction which is based on several different types of proxies is shown in  Figure 1(a) and is often referred to as  the 'hockey stick' with the 1000 to 1900 period in which temperatures were relatively stable  representing the handle and the post 1900 period in which global temperatures have risen about 0.7 C representing the blade.  This 'hockey stick' when it was published in 1999 was hugely controversial as it overturned the orthodox view that there had been a change in global temperatures of around 2 C over the last millennium with temperatures being highest at the beginning (Medieval Warm Period (MWP)) and lowest during the middle (Little Ice Age (LIA)) and twentieth century temperatures were considered to be somewhere in between.   Since 1999, there have been a number of other millennial temperature reconstructions based on proxies which also reproduced the 'hockey stick' trend.  But  Moberg, Dmitry, Holmgren, Datsenko. & Karlen, (2005) (abstract) shown in Figure 1b with other reconstructions is a recent one which shows rather more variability over the 1000 to 1900 period - 0.7 C for smoothed data-  and therefore it  restores to some extent, the pre-hockey stick orthodox view.


(a)


(b)

Figure 1 Millennial temperature reconstructions: (a) The Mann et al (1999) Northern Hemisphere reconstruction based on tree rings from AD 1000 1998. (b) A selection of later Northern Hemisphere reconstructions based on a variety of proxies including Moberg et al (2005) which shows much more variation over the last millennium than Mann's "Hockey Stick".

THIS chart also presents the various reconstructions and through colour coding where redder colours show the more recent reconstructions, it shows that there has been a trend since 1999 for reconstructions to portray progressively more variability over the last millennium and it clearly shows that the MWP & LIA are real periods of warmth and cold respectively in the last 1000 years but the magnitude of these climate anomalies varies between reconstructions. And there have been additional publications which have suggested that Mann et al (1999) may be underrating millennial temperature variability. Von Storch, Zorita,  Jones, Dimitriev, Gonzalez-Rouco, & Tett, (2004) argued that Mann et al (1998) may have underestimated temperature variations over the last millennium by a factor of two. They  identified  three main flaws with regression-based methods like Mann et al (1998):

  1. the fact that variations in proxy data are caused by other factors in addition to temperature reduces the variance in the temperature reconstruction
  2. a lack of variation in temperature in the period which is used to calibrate the proxy data to temperature greatly reduces variance in the temperature construction
  3. the lack of data from large regions of the northern hemisphere is also contributing to the reduced variance in Mann et al (1998)

ZORITA,  von Storch, Gonzalez-Rouco, Cubasch, Luterbacher, Legutke, Fischer-Bruns, & Schlese (2004) used a state-of-the-art climate model to simulate the global climate of the last 500 years (ie for the LIA) using estimated forcings of solar variability, volcanic activity and atmospheric concentrations of greenhouse gases and compared their results with those of various paleoclimate reconstructions. Their model simulated a climate colder than mean 20th century conditions almost globally and the degree of cooling was clearly larger than in most paleoclimate reconstructions of global and north hemispheric surface temperatures. There were two clear minima of mean global temperature around 1700 AD (the Late Maunder Minimum) and around 1820 AD (the Dalton minimum) relating to low sunspot activity. And importantly, the temperature trends simulated after the recovery from these minima were as large as the observed warming in the 20th century which implies that 20th century warming can simply be interpreted as a natural recovery from the LIA and not a response to increased greenhouse gases.

SO it is not just sceptics of man-made climate change who argue that Figure 1(a) minimises global temperature variations over the last millennium but some climate change scientists do as well. While it is true that Figure 1(a) includes error bars indicating large uncertainties for the 1000-1600 period, the estimated annual anomalies (which are plotted in black), even those of the warmest periods in the MWP are clearly much lower than values in most of the 20th century giving the impression that 20th century temperatures are unusual in the context of the last millennium. However, if you compare the warmest values shown by the error bars with 20th century temperatures, then you no longer have a hockey stick shape and only temperatures in the 1980s & 1990s are outside the warmest years in the MWP. Cubasch, Zorita, Gonzalez-Rouco, von Storch, & Fast (2004) did a climate model simulation for the last 1000 years in which global temperatures were 1 C colder during the LIA than today and were similar to today around 1200 AD in the MWP. They pointed out that this was more variability than shown by the paleoclimate reconstructions. So there has been a consensus emerging in the last few years that Mann et al (1999) probably does underrate millennial temperature variability and that the hockey stick trend probably doesn't apply because temperatures in the warmest parts of the MWP were comparable with temperatures in much of the 20th century until around 1980 when values MAY have exceeded those at anytime in the last millennium. This view is expressed in Temperature Variations in Past Centuries and the so-called "Hockey Stick"

IMPLICATION: paleoclimate millennial reconstructions with a hockey stick trend have been used by climate change scientists to portray 20th century temperatures as unusual in the context of the last millennium but in the last few years, newer reconstructions have restored both the MWP & LIA to a large extent and if you take into account the error bars of Mann et al (1998), only the post 1980 period is unusually warm in the context of the last millennium. This not only shows the fallibility of science & scientists, but also illustrates how scientists may "see what they want to see":  increased carbon dioxide in the atmosphere MUST cause global warming therefore 20th century temperatures MUST be warmer than those of the MWP!


3) DETECTION & ATTRIBUTION STUDIES ARE NOT ROBUST EVIDENCE OF MAN-MADE CLIMATE CHANGE AS CLAIMED BY SCIENTISTS

'DETECTION & Attribution' is the jargon used to describe studies which seek to match changes in climate to specific causes, both natural and anthropogenic. The IPCC definition of Detection & Attribution can be found here. These Detection & Attribution studies are claimed to be the most compelling evidence of man's influence on climate and support the IPCC claim that 'most global warming in the last 50 years is due to human activities'. Detecting & Attributing External Influences on the Climate System: A review of Recent Advances summarises this evidence. Detection and Attribution studies come in two forms:

  1. studies going back 150 years at most in which instrumental data (temperature; pressure; rainfall) are related to forcing factors
  2. studies going back to 2000 years in which the paleoclimate reconstructions are related to forcing factors.

1 are more compelling because not only are instrumental data used rather than paleoclimate data but also regional data are used instead of just a value for annual mean global temperature. This ought to give much greater confidence because the regional data are a much greater challenge for a climate model  to reproduce than simply mean global temperature which allegedly varies very little anyway. However these studies are invariably climate model based and we know (as discussed in weakness 2) all climate models are very sensitive to atmospheric levels of greenhouse gases which means these Detection & Attribution studies are not really any different to any other study based on climate models. The review linked to above mentions the results (in Figure 6) of a study by Stott et al (2003) which it claims is compelling evidence of the influence humans have probably had on regional climates. The results show that a climate model can crudely replicate the warming trends during the twentieth century in various regions around the world. These regions show two different types of warming trend: one in which warming is more or less continuous throughout the twentieth century and one in which the warming trend is interrupted during the 1950s, 1960s & early 1970s by cooling. So the model has basically attributed the long term warming trend to increasing greenhouse gases and mid-20th century cooling to sulphate aerosols (this fact is summarised here) and this is viewed as compelling evidence. With respect to sulphate aerosols being the cause of mid-20th century global and regional cooling, scientists are not confident of this because compared to greenhouse gas forcing, sulphate aerosol forcing is far more uncertain, principally because of limited understanding of the radiative properties of the aerosols and their effects on clouds (Jones & Mann, 2004). Also, sulphates from fossil fuel burning are washed out of the atmosphere by rain after a few days as are sulphates from volcanic eruptions. It is argued that only volcanic eruptions which are sufficiently large to eject sulphates into the stratosphere can cause a global cooling effect (Volcanoes & their effect on Climate) but climate change scientists argue that sulphates from coal-burning from the 1950s to mid-1970s caused a global cooling event even though they know these sulphates don't get into the stratosphere but are washed out of the atmosphere by rain after a few days. It beggars belief that scientists advocate this theory as an explanation for mid-20th century global cooling. The mid-20th century global cooling is dicussed in weakness 7 and it is argued that cold weather patterns explain the regional and global cooling from 1950-1975.

2 are not compelling at all because they rely on the paleoclimate reconstructions of the last millennium which as discussed in weakness 3 are uncertain and they depend on these paleoclimate reconstructions having a hockey stick trend which the most recent reconstructions don't show. In these millennial Detection & Attribution studies, either multiple regression techniques or climate models are used to explain the changes in annual global temperatures in terms of external climate forcings. These external climate forcings are solar, volcanic and greenhouse gases and these have been estimated over the last millennium by various techniques which of course have large uncertainties attached. Now these studies depend on global temperatures over the last millennium having a hockey stick trend because this means 20th century values are unusual and you need an unusual factor such as increased greenhouse gases to explain this. If global temperatures were as high in the MWP as in the twentieth century, then solar forcing can explain much of the 20th century warming and there is no need to invoke greenhouse gases. Crowley (2000) claims to account for 41-64% of 1000-1850 AD decadal-scale temperature variations in terms of changes in solar irradiance and volcanism whereas Hegerl, Crowley, Baum, Kim & Hyde (2003) places more emphasis on volcanism and less on solar irradiance. Minimising the solar influence on climate is essential if you are to argue that greenhouse gases are the cause of 20th century global warming and Stott, Jones & Mitchell (2003) claim that current climate models do underestimate the solar influence on 20th century global warming although they still argue that greenhouse gases account for late 20th century global warming.

IMPLICATION:   scientists are exaggerating the significance of Detection & Attribution studies by claiming they are compelling evidence of man-made climate change. These studies are not observations of the climate but are just climate model studies. And we know that climate models are very sensitive to the amounts of greenhouse gases in the atmosphere and some scientists have shown that climate models underrate the effects of solar activity. These two imperfections of models undermine their use as compelling evidence.


4) REGIONAL CLIMATE CHANGE IS INCORRECTLY BEING USED AS EVIDENCE OF MAN-MADE CLIMATE CHANGE

REGIONAL climate change is normal and this is clearly shown by instrumental data going back 300 years in the case of Europe and in the huge number of studies which have used paleoclimate data to reconstruct temperatures prior to the instrumental era for many different regions. Soon & Baliunas (2003) reviewed these extensive paleoclimate studies and presented the opinions of the original authors as evidence of regional climate change. The methodology of Soon & Balunias (2003) which was used to prove the existence of the MWP & LIA has been rightly criticised as they argued that a warm or dry anomaly was evidence of either the MWP or LIA which isn't necessarily correct. Nevertheless, the studies which Soon & Balunias (2003) summarised are real evidence of regional climate change. Today, the general public, the media and politicians are in such a paranoid state about climate change that they suspiciously blame man-made climate change for all sorts of weather events, be they normal (such as a violent summer thunderstorm or a severe winter gale) or unusual (the Boscastle floods), and quite frankly, this is absurd and can be compared to the Ancient Greeks attributing natural events to one of the range of Gods they worshipped. To be fair, this somewhat superstitious behaviour owes to the panic and sensationalism being spread by the IPCC and other meteorological organisations, experts whom people trust. But there is nothing new about regional climate change so it is incorrect to claim that current regional climate change is clear evidence of man-made climate change.

EUROPE is the region which has the most instrumental and documentary data which allows us to reconstruct the climate over the last millennium with more confidence than for any other region or indeed for the globe. One such reconstruction is for winter air temperature variations in western Europe during the early and high middle ages (Pfister, Luterbacher, Schwarz-Zanetti & Wegmann, 1998) which used 2500 documentary data. A fairly objective index of winter temperature was constructed using information on frost, freezing of water bodies, duration of snowcover and untimely activity of vegetation. It was concluded that "From AD 1090 to 1179 winter temperatures were at the level of the LIA, from AD 1180 to 1299 they were at that of the 20th century and that this warm stable 13th century climate supported subtropical plants such as olive trees in the Po valley (northern Italy) and fig trees around Cologne (Germany). The period AD 1300-1329 which marks the transition to the LIA was 1 C colder. It was concluded that the 1961-90 level of winter temperatures in western central Europe is still within the threshold of natural variability of the last thousand years, albeit at its upper boundary". Figure 10 in Pfister et al (1998) shows large swings in the winter index from both year to year and decade to decade indicating that the large swings in winter temperature in Europe over the last few decades associated with changes in the winter North Atlantic Oscillation (NAO) are nothing new (Figure 2). Indeed such swings in temperature are thought to be characteristic of the whole of the current interglacial but they were rare during the MWP. The NAO and EU circulation indices have been constructed back to 1500 (Luterbacher, Schmutz, Gyalistras, Jones, Davies, Wanner & Xoplaki, 2000) and although the observed tendency for positive winter NAO in much of the 20th century (Figure 2) is unusual in the context of the last 600 years, it is not unique. Both the 15th & 16th centuries appeared to have experienced periods of persistent positive NAO. And we know the period 1600-1850 was cold in Europe with a higher frequency of east and north-east winds in winter from documentary data and the cause of these colder weather patterns (negative winter NAO) is considered to be lower levels of solar activity (Shindell, Schmidt, Mann, Rind & Waple, 2001) or increased volcanism (Hegerl et al, 2003). So the dramatic change in winter weather in Europe from the cold 1960s, to the warmer 1970s, to the colder 1980s and then the warmer 1990s to present is quite normal in the context of data we have for the last 1000 years and the overall bias during the 20th century to more positive NAO relative to the LIA is accounted for by increased solar activity and reduced volcanism. While the changes in winter climate in Europe during the last few decades may well inspire awe and wonder amongst scientists and the general population, these changes cannot be used as evidence of man-made climate change. Climate can and does change naturally!

Figure 2 Relationship between mean winter European temperature anomaly from 1961-90 average and the winter (Dec-Feb) NAO 1900-2005 (r = 0.645; P<0.001)

SUMMER temperatures in Europe during the 20th century compared with the last 500 years show less warming than winters and with the exception of 2003, late 20th century European summers are no warmer than those of 1750-1800 which are considered the warmest of last 500 years (Luterbacher, Dietrich, Xoplaki, Grosjean, & Wanner, 2004; see Figure here). As 2003 was a single exceptional summer, it is inappropriate to read too much from this event and so we can conclude that although European summers in the late 20th century are certainly on the warm side, compared to summers of recent centuries which we know were cool in Europe, they are not unprecedented.

IMPLICATION: Europe is the only region in the world for which we have sufficient instrumental and proxy data to confidently reconstruct the climate of the last 500-600 years. And this is a period which we know from paleoclimate and model reconstructions of global temperatures over the last millennium (Figure 1(b)) was cooler than the twentieth century but both winter and summer European temperatures during the late 20th century (with the exception of a single summer, 2003) are within the bounds of natural variability of these colder centuries. This is at variance with all the hullabaloo and hysteria about the current warmth of the European climate and shows that regional climate change is being incorrectly cited as evidence of man-made climate change.


5) THE 300 YEAR LONG CENTRAL ENGLAND TEMPERATURE RECORD SHOWS SEASONAL WARMING WHICH SUGGESTS THAT THE MAGNITUDE OF GLOBAL WARMING IS NOT LARGE

THE CENTRAL ENGLAND TEMPERATURE (CET) SERIES (Manley, 1974) was the lifetime work of the late Professor Gordon Manley whose dogged determination and meticulous work gave science its most accurate measure of climate change over the last three hundred years. This valuable and highly respected temperature record is shown in Figure 3 and several features are evident:

  • temperature variations are somewhat cyclical rather than random with years with high temperatures being grouped together and years with low temperature being grouped together
  • there is a long term warming trend but this only commenced around 1920
  • the 1989-2004 period is clearly a warm part  of one cycle and is certainly the warmest period in the record but it is not much warmer than previous warm periods

AND the CET can be considered to be a global temperature record for the following reasons:

  • there is a highly significant correlation between annual CET and the northern hemisphere temperature record since 1881 (Figure 4)
  • the UK's position on the eastern side of the North Atlantic with prevailing westerly winds in all seasons ensures that the UK cannot avoid the effects of any significant change in global temperature
  • there are precedents for a temperature record from a local area being viewed as a global temperature record: the Greenland and Antarctic ice cores in which the ratios of the isotopes of oxygen in air trapped within the ice are used to construct a historical temperature record at that site which is then used to represent global temperatures over several thousand years
  • and finally, the mobility of the atmosphere which behaves like a fluid in motion flowing around the surface of the Earth ensures heat/cold is distributed right around the globe. This is why the effects of man-made climate change are expected to be global and this means any significant rise in global temperature should be evident in a long temperature record of a specific region such as the CET.

COMPARED with temperature reconstructions based on tree rings or ice cores which are called proxies for temperature, the CET is a real temperature record constructed from measurements made by thermometers so it is far superior in quality.  One issue with temperature records prior to 1880 when Stevenson screens were introduced is that daytime maxima were too high because of  inadequate shielding from sunlight. Manley was aware of this issue and the data have been corrected for this and a multitude of other factors that Manley thought appropriate after meticulous comparisons from overlapping records from different sites in central England (Manley, 1974). Manley had low confidence for data prior to 1700 which is reflected in values being rounded to a half degree  and data from 1700-1720 have less confidence than later values as it relies heavily on data from Utrecht, Netherlands. However, the data post 1720 were considered reliable by Manley and his work was and still is highly regarded by scientists and represents the longest temperature record in the world. Since Professor Manley's death in 1981, the CET has been maintained by the Hadley Centre of the UK Met Office.

SO the CET is not only a highly respected temperature record for the UK, the CET can with justification be viewed as a measure of global temperature change over the last 300 years and analysed to test for a significant change in global temperature. Comparing the CET (Figure 3) with the Mann et al (1999) global temperature reconstruction (Figure 1(a)), it is certainly true that the 20th century appears warmer than preceding centuries in both Figures but the 20th century warming is much more dramatic for global temperatures. By considering the warmest values shown by the error bars in Figure 1(a) for the 17th & 18th centuries, a more modest warming trend consistent with Figure 3 is obtained.

Figure 3 Annual values of the Central England Temperature (CET) together with ten and 30 year running means: 1659-2004


Figure 4   Relationship between the northern hemisphere annual temperature anomaly (CRU) and annual CET 1881-2003 (r = 0.535; P<0.001).


T-TESTS (two-tailed, unpaired) were used to compare monthly values of CET from 1970-2004 with nine preceding thirty year periods commencing 1700-1729 and comparative tests were done for seasonal and annual values. Table 1 shows the results which can be summarised as follows:

  • February, April & June gave no significant results while May & July gave only 2 (out of 9) significant results at the 5% level: therefore in these five months, the 1970-2004 data are similar to data in the nine preceding 30 year periods
  • the remaining seven months gave a number of significant results including some at the 1 or 0.1% level indicating that the 1970-2004 data are different from the earlier nine 30 year periods
  • all four seasons and the annual data gave highly significant results (1 or 0.1%) but summer only gave one such result

Table 1 Mean values of CET for 1971-2004 compared with nine preceding 30 year periods commencing 1700-1729: monthly, seasonal and annual values and results of t-tests comparing 1971-2004 values with earlier 30 year periods

                                   
      Mean CET (C)  for each 30 year period and result of t-tests comparing 1970-2004 mean with earlier periods
        * significant at 5% level     ** significant at 1% level     *** significant at 0.1% level  
  __________________________________________________________________________________________
                                   
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Win Spr Sum Aut Ann
__________________________________________________________________________________________________
1700-29 3.1* 3.7 5.0** 7.9 11.3 14.4 15.9 15.8 13.5 9.5*** 6.2** 4.0** 3.6** 8.0** 15.4 9.7*** 9.2***
1730-59 3.4 3.8 5.2** 7.7 11.2 14.5 16.1 15.8 13.8 9.5** 6.0** 4.1* 3.8* 8.1** 15.5 9.7** 9.3**
1760-89 2.3*** 3.6 4.8** 8.0 11.5 14.6 16.2 15.8 13.4 9.2*** 5.5*** 3.8** 3.2*** 8.1* 15.5 9.4*** 9.1***
1790-19 2.7** 4.2 5.2** 7.9 11.2 14.2 15.9 15.7* 13.1* 9.6* 5.5*** 3.2*** 3.4*** 8.1* 15.2 9.4*** 9.0***
1820-49 2.6** 3.8 5.5* 8.0 11.6 14.6 15.7* 15.3** 13.0** 9.7* 6.3** 4.5 3.6** 8.4 15.2* 9.7*** 9.2***
1850-79 3.7 4.2 5.2** 8.3 10.8* 14.3 16.0 15.6** 13.2* 9.7* 5.4*** 4.0 4.0 8.1** 15.3 9.4*** 9.2***
1880-09 3.4 3.9 5.1** 7.7 10.8* 14.1 15.8* 15.2** 13.2* 9.1*** 6.3* 3.9** 3.7** 7.9*** 15.0** 9.6*** 9.1***
1910-39 4.4 4.4 5.7 7.8 11.5 14.2 15.9 15.6* 13.3* 9.7* 6.1* 4.7 4.5 8.3 15.2* 9.7*** 9.4**
1940-69 3.2* 3.6 5.8 8.5 11.4 14.5 16.0 15.7* 13.7 10.5 6.5 4.4 3.7* 8.6 15.4 10.2 9.5*
1970-04 4.2 4.3 6.3 8.1 11.5 14.2 16.5 16.3 13.8 10.5 7.0 5.0 4.5 8.6 15.7 10.4 9.8
                                   
          Number of significant t-tests at each level (Maximum 9)        
                                   
__________________________________________________________________________________________________
5% 2 0 1 0 2 0 2 3 4 4 2 1 2 2 2 0 1
1% 2 0 6 0 0 0 0 3 1 1 3 3 3 3 1 1 2
0.1% 1 0 0 0 0 0 0 0 0 3 3 1 2 1 0 7 6
                                   
Totals 5 0 7 0 2 0 2 6 5 8 8 5 7 6 3 8 9
___________________________________________________________________________________________________

 

IN addition to the t-tests, the monthly, seasonal and annual data for 1970 to 2004 are also compared graphically with the data from the nine preceding 30 year periods in Figures 6 to 22. First, it is appropriate to present a graph which compares monthly temperature data which are significantly different. Figure 5 compares August mean temperatures at Aberdeen/Dyce with August CET and a clear separation of the two datasets is obvious: all t-tests between the Aberdeen & CET data give highly significant results (at the 0.1% level) indicating that August temperatures at these two sites are different.

Figure 5 Comparison of August mean temperatures at Aberdeen/Dyce with Central England (CET) from 1880: data from 1970-2004 compared with
 three preceding consecutive 30 year periods


FIGURES 6 to 22 have a similar format to Figure 5 but compare CET from 1970 to 2004 with the nine preceding consecutive 30 year periods shown in Table 1, for monthly, seasonal and annual values. A few comments are presented for each graph   .

Figure 6 Comparison of January CET from 1970 to 2004 with data from nine preceding 30 year periods

JANUARY comments:

  • 1988-2004 data are noticeably warm whereas 1970-1987 data are typical of the 300 years data
  • although 1988-2004 data are warm, only 1990 is as warm as the ten warmest Januaries since 1700
  • the coldest 30 year period is 1760-1789 (2.3 C) and the warmest 30 year period is 1910-1939 (4.4 C) (1970-2004: 4.2 C; Table 1)
  •  

Figure 7 Comparison of February CET from 1970 to 2004 with data from nine preceding 30 year periods

FEBRUARY comments:

  • 1997-2004 data are noticeably warm but data from 1970-1996 are typical of the 300 years data
  • the 1997-2004 period includes three anomalously warm months: 1997; 1998 & 2002. 1998 was third warmest since 1700 (jointly with 1990)
  • 1986 was the fifth coldest February since 1700
  • the coldest 30 year periods are 1760-1789 & 1940-1969 (3.6 C) and the warmest 30 year period is 1910-1939 (4.4 C) (1970-2004: 4.3 C; Table 1)
  •  

Figure 8 Comparison of March CET from 1970 to 2004 with data from nine preceding 30 year periods

MARCH comments:

  • 1988-2004 data are noticeably warm whereas 1970-1987 data are typical of the 300 years data
  • 1997 & 1990 are the third and fourth warmest Marches since 1700
  • the coldest 30 year period is 1760-1789 (4.8 C) and the warmest 30 year period is 1970 to 2004 (6.3 C) (Table 1)
  •  

Figure 9 Comparison of April CET from 1970 to 2004 with data from nine preceding 30 year periods

APRIL comments:

  • 1970-2004 data are typical of the 300 years data
  • 2003 & 2004 are fairly warm but their ranking is just outside the top 20 warmest Aprils
  • the coldest 30 year periods are 1730-1759 & 1880-1909 (7.7 C) and the warmest 30 year period is 1940-1969 (8.5 C) (1970-2004: 8.1 C; Table 1)
  •  

Figure 10 Comparison of May CET from 1970 to 2004 with data from nine preceding 30 year periods

MAY comments:

  • 1998-2004 data are noticeably warm but 1970-1997 are typical of the 300 years data
  • 1992 is the fifth warmest May since 1700 & 1998 and 1999 are in the top twenty warmest
  • the coldest 30 year periods are 1850-1879 & 1880-1909 (10.8 C) and the warmest 30 year period is 1820-1849 (11.6 C) (1970-2004: 11.5 C; Table 1)
  •  

Figure 11 Comparison of June CET from 1970 to 2004 with data from nine preceding 30 year periods

JUNE comments:

  • 1970-2004 are typical of the 300 years data
  • 2003 is the fifteenth warmest June since 1700
  • the coldest 30 year period is 1880-1909 (14.1 C) and the warmest 30 year periods are 1760-1789 & 1820-1849 (14.6 C) (1970-2004: 14.2 C; Table 1)
  •  

Figure 12 Comparison of July CET from 1970 to 2004 with data from nine preceding 30 year periods

JULY comments:

  • 1989-2004 are noticeably warm whereas 1970-1987 are mostly typical of the 300 years data except for 1976 & 1983
  • 1983, 1995 & 1976 are the first, third equal & fourth warmest respectively since 1700
  • the coldest 30 year period is 1820-1849 (15.7 C) and the warmest 30 year period is 1970-2004 (16.5 C) (Table 1)
  •  

Figure 13 Comparison of August CET from 1970 to 2004 with data from nine preceding 30 year periods

AUGUST comments:

  • 1995-2004 are noticeably warm whereas 1970-1994 are mostly typical of the 300 years data
  • 1995, 1997 & 1975 are the warmest three Augusts since 1700
  • the coldest 30 year period is 1880-1909 (15.2 C) and the warmest 30 year period is 1970-2004 (16.3 C) (Table 1)
  •  

Figure 14 Comparison of September CET from 1970 to 2004 with data from nine preceding 30 year periods

SEPTEMBER comments:

  • 1998-2004 are noticeably warm whereas 1970-1997 are typical of the 300 years data
  • 1999 was the sixth warmest September since 1700
  • the coldest 30 year period is 1820-1849 (13.1 C) and the warmest 30 year periods are 1730-1759 & 1970-2004 (13.8 C) (Table 1)
  •  

Figure 15 Comparison of October CET from 1970 to 2004 with data from nine preceding 30 year periods

OCTOBER comments:

  • most Octobers 1970-2004 are warm suggesting that climate change has occurred in this month
  • 2001 & 1995 are the warmest and third warmest October respectively since 1700
  • the coldest 30 year period is 1880-1909 (9.1 C) and the warmest 30 year periods are 1940-1969 & 1970-2004 (10.5 C) (Table 1)
  •  

Figure 16 Comparison of November CET from 1970 to 2004 with data from nine preceding 30 year periods

NOVEMBER comments:

  • 1994-2004 are noticeably warm but 1970-2004 generally are warm relative to earlier 30 year periods
  • 1994 is the warmest and 2001 equal eleventh warmest November since 1700
  • the coldest 30 year period is 1850-1879 (5.4 C) and the warmest 30 year period is 1970-2004 (7.0 C) (Table 1)
  •  

Figure 17 Comparison of December CET from 1970 to 2004 with data from nine preceding 30 year periods

DECEMBER comments:

  • 1970-2004 are generally warm relative to earlier 30 year periods
  • 1974 is equal warmest December with 1934 since 1700
  • the coldest 30 year period is 1790-1819 (3.2 C) and the warmest 30 year period is 1970-2004 (5.0 C) (Table 1)
  •  

Figure 18 Comparison of winter (Dec-Feb) CET from 1970 to 2004 with data from nine preceding 30 year periods

WINTER comments:

  • 1970-2004 are generally warm relative to earlier 30 year periods and post 1997 noticeably so
  • 1989, 1975, 1990 are the third, fourth & fifth warmest winters respectively since 1700
  • the coldest 30 year period is 1760-1789 (3.2 C) and the warmest 30 year period is 1970-2004 (4.5 C) (Table 1)
  •  

Figure 19 Comparison of spring (Mar-May) CET from 1970 to 2004 with data from nine preceding 30 year periods

SPRING comments:

  • 1988-2004 are noticeably warm but 1970-1987 are mostly typical of the 300 years data
  • 1992 & 1999 are the third & fourth warmest springs respectively since 1700
  • the coldest 30 year period is 1880-1909 (7.9 C) and the warmest 30 year periods are 1940-1960 & 1970-2004 (8.6 C) (Table 1)
  •  

Figure 20 Comparison of summer (Jun-Aug) CET from 1970 to 2004 with data from nine preceding 30 year periods

SUMMER comments:

  • 1994-2004 are noticeably warm but 1970-1993 are mostly typical of the 300 years data except for 1975, 1976 & 1983
  • 1976, 1995 & 2003 are the warmest, third & fourth warmest summers respectively since 1700
  • the coldest 30 year period is 1880-1909 (15.0 C) and the warmest 30 year period is 1970-2004 (15.7 C) (Table 1)
  •  

Figure 21 Comparison of autumn CET from 1970 to 2004 with data from nine preceding 30 year periods

AUTUMN comments:

  • 1970-2004 are noticeably warm
  • 1978 & 1995 are the sixth & seventh warmest autumns respectively since 1700
  • the coldest 30 year period are 1760-1789, 1790-1809 & 1850-1879 (9.4 C) and the warmest 30 year period is 1970-2004 (10.4 C) (Table 1)
  •  

Figure 22 Comparison of annual CET from 1970 to 2004 with data from nine preceding 30 year periods

ANNUAL comments:

  • 1989-2004 are noticeably warm and 1970-1988 are somewhat warm
  • 1990 & 1999 are joint equal warmest year with 1949 and 11 of the last 16 years have had an annual temperature above 10 C
  • the coldest 30 year period is 1790-1819 (9.0 C) and the warmest 30 year period is 1970-2004 (9.8 C) (Table 1)
  •  

SUMMARISING Figures 6 to 22:

  • in seven months (Jan; Feb; Mar; May; Jul; Aug; Sep), recent years (either post 1988 or post mid-1990s) are noticeably warm but earlier years in the 1970-2004 period were generally typical of the 300 years data
  • in October, November & December, 1970-2004 data are noticeably warmer than earlier 30 year periods, thereby showing to some extent a separation from the rest of the data (as exhibited in Figure 5) indicating a significant difference (Table 1)
  • in April & June, 1970-2004 data are typical of the 300 years data
  • in winter and autumn, the full 1970-2004 period was noticeably warm whereas in spring and summer, only post 1988 data and post 1993 data respectively were noticeably warm and most previous data back to 1970 were fairly typical of the 300 years data
  • the annual data in Figure 22 show a clear separation for the 1989-2004 period and 1970-2004 generally are warm relative to the 300 years data and are significantly different (Table 1)

IN summary of Table 1 and Figures 6 to 22, the 1970-2004 period is warmer than earlier 30 year periods but this warming is seasonal being most intense from October to December but 1970-2004 mean temperatures in some months, namely February, April & June are no different from mean temperatures in any of the nine preceding 30 year periods and in two other months (May & July), there was only a weak significant difference with two earlier 30 year periods. The CET does not support the hockey stick (Figure 1a) which implies that 20th century temperature data are much higher and significantly different to 18th and 19th century temperatures.

IT should be noted that seasonal and annual data are not independent of the monthly data. For example, autumn is the season with most significant t-tests (Table 1) because autumn months individually had the most significant t-tests. And a second factor which accounts for the significant results for the seasonal and annual data is the strong bias for months with above average temperatures since 1988 which is apparent in Figure 23.

Figure 23 Monthly anomalies of mean Central England Temperature (CET) relative to 1961-90 average: January 1981 to August 2006 (this graph is updated monthly

THIS strong bias to months with above average temperatures is caused by a high incidence of warm weather patterns (i.e weather patterns which bring higher than average temperatures). This has been conclusively demonstrated in UK Climate Change since 1881 and the 1989-2002 warm period in detail and Are the warm years in the UK since 1988 caused by a high incidence of warm weather patterns or global warming?. Fortunately, it is not necessary to read these two long articles to see that the notable run of warm months since 1988 (Figure 23) owes to warm weather patterns. Figure 24 shows that an above average incidence of westerly winds (positive North Atlantic Oscillation (NAO)) in most winters 1989-2002 explains the numerous mild winters in this period: westerly winds off the Atlantic bring mild Atlantic air across the UK & Europe. The mildest winters occurred in the 1989-1994 period in which the NAO was anomalously positive. The causes of long term trends in the winter NAO are not well understood but two natural factors certainly contributed to the 1989-1994 positive NAO: the high peak of sunspot cycle 22 around 1990 and the eruption of Mount Pinatubo in 1991 which injected sulphate aerosols into the stratosphere. These two factors strengthen the winter stratospheric vortex which causes stronger westerlies in the atmosphere around the northern hemisphere.

Figure 24 Relationship between mean winter temperature anomaly (December to February) of Europe (stations defined here)
from 1961-90 average and the winter (December to February) NAO index 1900-2004 ( r = 0.662; P < 0.001)


WARM summers in the UK & Europe have also been characteristic of the 1989-2004 period and this has been caused by a higher than average incidence of anticyclonic weather patterns and southerly airstreams (not shown).   Figure 25 shows the relationship (r = -0.5284; P<0.001) between summer CET and the summer C index. A low C index indicates above average incidence of anticyclonic weather patterns and anticyclonic conditions in summer bring clear skies and therefore longer hours of sunshine which of course means it gets warmer than average.

Figure 25 Relationship between mean summer CET and the summer C index 1881-2004 ( r = -0.528; P < 0.001)


CLEARLY, there has been a strong bias to warm weather patterns in the 1989 to 2004 period (Figures 24 & 25) and this accounts for the strong bias to months with above average temperature post 1988 in Figure 23. This warmth does not owe directly to higher global temperatures. And the paradox between the fact that in five months of the year, 1970-2004 data are not significantly different from nine earlier 30 year periods but seasonal and annual data are significantly different (Table 1) owes to the persistent run of above average months since 1988.  Some of these warm months have been exceptionally warm (see comments in Figures 6 to 22) but the majority of months 1989-2004 have not but have simply been somewhat warm (Figure 23). To show that the warming of the CET is not exceptional, Figure 26 shows average values of monthly CET for several periods in the last 300 years and compares them with 1961-90 average  monthly temperatures for Aberdeen (57.2 N  2.2 W)  and Nantes (47.2 N  1.6 W). The CET represents a region half way between Aberdeen and Nantes: for example Birmingham is located at 52.5 N and 1.7 W but in global terms these three sites are all located in a small part of a big world but nevertheless have quite different climates. Of the four CET periods presented in Figure 26, the 1989 to 2004 period clearly stands out with respect to January to March and July to August and Figures 23 & 24 have provided meteorological explanations for these anomalies. The other three CET periods show that 1961-90 mean temperature values are similar to both 1700-1899 values and 1901-1990 values supporting the results presented in Table 1 and Figures 6 to 22. In contrast, the 1961-90 mean monthly  temperatures of Aberdeen and Nantes clearly are different from the CET mean monthly temperatures showing that the magnitude of warming in the CET to date really isn't that large and it is gross exaggeration for anyone to suggest that the magnitude of either UK or global warming to date is equivalent to a significant shift of the world's climate zones, thereby causing serious effects on the life cycles of plants and animals. The CET simply does not portray a warming of the same magnitude as implied by Mann et al (1998) shown in Figure 1a. The 20th century was certainly warmer than the 18th & 19th centuries in central England (Figure 3) but this warming has been seasonal which is inconsistent with the concept of a dramatic rise in global temperatures which would cause all year round warming.


Figure 26 Comparison of mean monthly Central England Temperature (CET) for four different periods in the last 300 years with 1961-90 mean monthly temperature values at Aberdeen, Scotland and Nantes, France.

IMPLICATION: the seasonality of twentieth century warming in central England (mainly autumn & winter) relative to 18th & 19th century temperatures is inconsistent with the dramatic warming of Mann et al. (1999) shown in Figure 1(a). And this warming of the CET from 1970-2004 is not of sufficient magnitude to give a similar climate to places a few degrees latitude to the south such as Nantes except in January-March but we know that strong westerly winds at this time of year from 1989-2002 explains this anomalous warmth. But in spite of these facts, the recent warming of the UK climate is being cited as evidence of man-made climate change when it is clear internal climate variability (changes in regional weather patterns: the NAO) is the overriding factor in recent UK climate change.


6) COLD WEATHER PATTERNS APPEAR TO ACCOUNT FOR MID-20TH CENTURY COOLING, NOT SULPHATE AEROSOLS FROM COAL BURNING

THE graph of the global surface temperature during the 20th century (Figure 27) is familiar to us all because it is brandished by climate change scientists as evidence of man-made climate change owing to the dramatic long term warming trend it portrays. Of course, it does not show evidence of man-made climate change but simply climate change as the graph presents no information on the causes of the warming trend. But a major feature of this graph is the interruption of the warming trend during the 1950s, 1960s & early 1970s when global temperatures fell slightly. Why was this? Climate Change scientists attribute this global cooling to increased sulphate aerosols in the atmosphere from increasing coal burning in developed countries after the second world war and the argument goes on to explain the cessation of this cooling during the mid-1970s on the introduction of technologies to reduce sulphate emissions from power stations. The theory argues that the sulphate aerosols either scattered incoming solar radiation directly, thereby cooling the surface, or indirectly by increasing cloud amounts. There are several aspects of this theory that inspire scepticism:

  1. the beginning and end of the cooling phase are quite abrupt but the theory used to explain this global cooling cannot logically account for such abrupt changes
  2. the implication that the warming trend is man-made from increased greenhouse gases and the mid-20th century cooling phase is man-made from sulphate aerosols leaves little room for natural factors to contribute to 20th century global temperature variability which effectively underrates natural variability to a minor player
  3. sulphates from fossil fuel burning are washed out of the atmosphere by rain after a few days as are sulphates from volcanic eruptions. It is argued that only volcanic eruptions which are sufficiently large to eject sulphates into the stratosphere can cause a global cooling effect (Volcanoes & their effect on Climate) but climate change scientists argue that sulphates from coal-burning from the 1950s to mid-1970s caused a global cooling event even though they know these sulphates don't get into the stratosphere but are washed out of the atmosphere by rain after a few days. It beggars belief that scientists advocate this theory as an explanation for mid-20th century global cooling.


Figure 27
Annual global temperatures 1900 to 2004 according to two measures of land-ocean surface temperatures (CRU  & GHCN) and two measures of lower atmosphere temperatures (radiosonde balloon since 1958 and Christy & Spencer LT5.2 satellite data since 1979) .


IN FACT scientists are far less certain of this sulphate aerosol forcing than they are of greenhouse gas forcing, principally because of limited understanding of the radiative properties of aerosols and their effects on clouds and also because they acknowledge the effect is regional and it can only be crudely estimated from past fossil fuel use in a region (Jones & Mann, 2004). There are no measurements of this effect during the 20th century, it is just a theory and an essential theory for the man-made climate change argument because without it, the climate models (and therefore climate change scientists) cannot account for the mid-20th century cooling trend. An alternative theory for this mid-20th century cooling trend is internal climate variability or more specifically global cooling induced by changes in regional atmospheric circulations.

TEMPERATURE records spanning the twentieth century for various stations of the northern hemisphere are available from the Goddard Institute for Space Studies and the author has used these data to construct a number of regional temperature records for the twentieth century: 1990s: the warmest decade of the twentieth century? describes the construction of these records and presents the results: basically, annual mean temperature data from ten stations were used to construct a mean annual temperature anomaly (from 1961-90 averages) for each region from 1900 to 2001. These regional temperature records from 1900-2001 are  presented below in Figures 28 to 30 and although each region to some extent has a unique trend, the long term trends visible in the CET and the northern hemisphere temperature record (Figure 4) are present in all the regional temperature records: warming from 1900 until the 1940s, cooling in the 1950s, 1960s and first half of the 1970s followed by a strong warming trend from 1975 onwards; and overall warming of around 1 C.

  

 




TABLE 2 shows the correlation matrix between annual CET anomalies and these 12 regional anomalies and in eight cases, the correlation was positive and highly significant, in one case (North Africa), it was positive & weakly significant, and in three cases (W & E Canada; SW Asia) the correlation was non-significant. This confirms that the same warming/cooling/warming trend present in the CET also occurs in most other northern hemisphere regions and this illustrates two important points:

  • the world has warmed since 1900: global warming is a reality but it does not necessarily follow that this warming relative to earlier centuries is as dramatic as the hockey stick suggests (Figure 1a) or that it was caused by burning fossil fuels
  • the mobility of the atmosphere (it is a fundamental tenet of meteorology that the atmosphere is well-mixed) distributes any warming/cooling around the globe: meaning the same warming/cooling trends are evident in most regions of the northern hemisphere

TABLE 1 and Figures 6 to 22  show that in spite of the alleged advantage of the highest global temperature in at least a thousand years (which is claimed by scientists on the basis of the paleoclimate reconstructions),  mean CET 1970-2004 in five months of the year are not significantly warmer than in nine earlier 30 year periods indicating a seasonality in the warming. Is the CET unrepresentative of the globe? Probably not because most other northern hemisphere regions show similar warming trends (Figures 28-30; Table 2) so presumably if 300 years temperature data were available for these regions too, then some seasonality in the warming trends might be expected as well.


Table 2 Correlation matrix showing the relationships between annual CET anomalies and the annual temperature anomalies of different regions of Eurasia and North America 1900-2001

 

  Correlation Coefficients          
                         
_____________________________________________________________________________________________________________________________________
CET 1.00                      
Europe 0.83*** 1.00                    
Arctic 0.37*** 0.42*** 1.00                  
West Russia 0.37*** 0.36*** 0.29** 1.00                
Central Russia 0.45*** 0.60*** 0.20* 0.58*** 1.00              
East Russia 0.47*** 0.47*** 0.48*** 0.59*** 0.48*** 1.00            
West Canada 0.10 0.01 0.15 0.28** 0.05 0.06 1.00          
East Canada -0.14 -0.08 -0.03 -0.07 -0.05 -0.29** 0.29** 1.00        
West USA 0.32*** 0.30** 0.32** 0.29** 0.20* 0.30** 0.35*** 0.07 1.00      
East USA 0.33*** 0.31** 0.23* 0.11 0.17 0.01 0.13 0.19 0.43*** 1.00    
North Africa 0.22* 0.36*** 0.40*** 0.22* 0.03 0.08 0.34*** 0.39*** 0.31** 0.34** 1.00  
SW Asia -0.01 0.00 0.20* 0.14 0.08 -0.13 0.26** 0.48*** 0.36*** 0.24* 0.54*** 1.00
SE Asia 0.40*** 0.43*** 0.36*** 0.59*** 0.30** 0.29** 0.29** 0.19*** 0.39*** 0.32** 0.52*** 0.48***
  CET Europe Arctic W Russ Cen. Russ E Russ W Can E Can W  USA E USA N Africa SW Asia
_____________________________________________________________________________________________________________________________________

 

Correlation significant at : * 5% level;     ** 1% level;     *** 0.1% level

  • the NAO: pressure difference between Iceland and the Azores
  • the AO: pressure difference between the arctic and about 37-45 N (closely related to the NAO)
  • the PDO is slightly different as it relates to the North Pacific temperature distribution north of 20 N but as it is correlated with atmosphere pressure in the Pacific, it is another teleconnection
  • the SOI: difference in pressure between Tahiti in the middle of the Pacific and Darwin, Australia: also referred to as ENSO.

  • mid-20th century cooling in Europe was associated with negative NAO r = 0.538, P<0.001
  • mid-20th century cooling in eastern Russia was associated with negative AO r = 0.587, P<0.001
  • mid-20th century cooling in western USA was associated with negative PDO r = 0.284, P<0.01
  • mid-20th century cooling in eastern USA was associated with negative NAO & neutral SOI F = 3.73, P = 0.03
  • mid-20th century cooling in western Canada was associated with negative PDO r=0.614, P<0.001

EVIDENTLY, teleconnections/changes in regional atmospheric circulation have had a large & significant effect on regional temperature change from 1900 to 2001 and to a large extent appear to have caused the mid-20th century global cooling so the claim by climate change scientists that sulphate aerosols caused this global cooling looks very dodgy for this reason & for the reasons listed in points 1 to 3 mentioned at the beginning of this section. And because changes in atmospheric circulation strongly influenced regional temperature over the 20th century and and appear to have caused the mid-20th global cooling,  it is valid to pose the question, to what extent did changes in atmospheric circulation cause the global warming at the beginning and end of the 20th century ?  Mann et al (1998) identified both SOI & NAO like  temperature variations as the second and third most important trends (the first being the long term warming trend) in their proxy reconstruction of global temperature from 1400 AD which confirms that these changes in atmospheric circulation have a big impact on regional temperatures. But scientists do not acknowledge these changes in atmospheric circulation as factors which can cause significant changes in global temperatures: the consensus is that natural internal climate variability from factors such as changes in atmospheric circulation  is minimal and the paleoclimate & model reconstructions of the last millennium support this view by showing minimal variation . However, negative SOI (an El Nino)  is acknowledged as a factor causing short-term global warming and indeed is considered to be the main cause of  the warmest year on record (1998) which contradicts this. Global surface temperatures rose 0.4 C from 1996 to 1998 (Figure 27) in response to the strong 1997-98 El Nino and lower trophosphere temperatures (Figure 31) rose a similar amount which is a massive change unprecedented in the last millennium according to Figure 1(a). Such a large change in the space of just a couple of years is more proof that these paleoclimate reconstructions massively underrate past climate variations and only by taking into account the large error margins can you get a semi-realistic picture of  global temperatures over the last millennium: this means the hockey-stick trend is completely misleading. Returning to El Ninos, changes in SOI/ENSO are known to have global impacts and these collectively are sufficient to cause a short-term change in annual global temperature of  up to 0.8C which is of a similar magnitude to the long term warming trend of global temperature over the 20th century of 0.6  +-0.2 C. Often  the warming/cooling effect of changes in SOI/ENSO are short-term but multi-decadal trends also occur and since the mid-1970s, there has been a marked trend to stronger El Ninos which MUST have contributed to the rise in global temperatures since then.

Figure 31 Satellite measurements of the temperature of the lower atmosphere from January 1979 to August 2006 presented as monthly anomalies from the 1979-98 average for the globe and for the northern and southern hemispheres (Christy & Spencer analysis. LT5.2 data here)

Figure 32 Comparison of ten year running means of Jan-Mar NAO and northern hemisphere surface temperature anomaly from 1961-90 average from 1900-2003

HURRELL (2003) states that “The NAO accounts for much of the interannual and longer-term variability evident in northern hemisphere surface temperature” but the recent monograph neither provides any mechanistic process by which the NAO can change northern hemisphere temperature nor does it acknowledge the NAO as a factor in the rise in global temperatures during recent decades. This is illogical given Hurrell's statement above and perhaps can be explained by scientists reluctance to attribute climate change to natural internal climate variability in the current situation in which rising greenhouse gases are being blamed for all climate change. The NAO, AO & global warming: how closely related?  examines the contribution the NAO & AO has made to the global warming trend and concluded "While the NAO & AO may contribute to hemispheric & regional warming for multi-year periods, ....the large scale features of the global warming trend over the last 30 years is unrelated to the NAO & AO". So some scientists do accept that positive NAO has contributed to some of the northern hemisphe warming of recent decades supporting the hypotheses articulated in this article but it didn't explain how the NAO may contribute to fluctuations in northern hemisphere temperature.

SO how might the positive phase of the NAO 1900-1940s & 1975-present cause climate feedbacks which leads to global warming?  Four plausible feedbacks are described below:

1) reduced continental winter cooling across North America at 40-50 N & Eurasia 50-60 N (these regions are known to warm by up to 2 C in positive NAO winters; Hurrell, 2003):
the mobile zonal flow across the US and Europe/Russia increases temperatures, humidity and cloud cover and the latter two factors will reduce the amount of outgoing longwave radiation which escapes into space during the course of the winter.

2) reduced winter albedo from reduced snow cover across North America at 40-50 N & Eurasia 50-60 N: the mobile zonal flow across the US and Europe/Russia increases temperatures, humidity and cloud cover which overall is likely to reduce snow cover extent although increased precipitation may increase it locally. This will mean less short wave radiation is reflected back into space and more is absorbed by the surface relative to a negative NAO winter.

3) reduced winter cooling in the arctic: while it is true that the arctic is cold in positive NAO winters relative to negative NAO winters, this is because the cold air is trapped their by the strong westerlies further south and cannot escape to lower latitudes which it does in negative NAO winters. Positive NAO brings lower pressure and higher cloud amounts and humidity into the arctic so that outgoing longwave radiation would be reduced in a positive NAO winter relative to a negative NAO winter.

4) reduced all-year round albedo from arctic sea ice: positive NAO means strong south westerly winds in much of of the Greenland/Nordic seas which pushes Atlantic ocean warmth northwards into the arctic and melts the sea ice from underneath. This was very true in the 1989 to 1995 period when a big increase in wave heights in this region was measured by satellites. It is widely accepted that the positive NAO/AO of recent decades has caused a reduction in arctic sea ice and this means more ocean is exposed and this absorbs short wave radiation in contrast to sea ice which reflects it back into space.

SO we have four climate feedbacks from positive NAO which MUST lead to a net increase in energy contained in the ocean/atmosphere system when you have a long term increase in the NAO like we have seen since 1960 (Figure 32). This MUST have made a contribution to global warming over this period but we simply don't have the measurements of outgoing and incoming radiation within the climate system to enable us to accept or reject the hypotheses that these  four plausible feedbacks have made significant contributions to global warming over the last 50 years. The IPCC view is that "most global warming over the last 50 years is from human activities" so by implication any contribution from internal climate variability such as the NAO must be small.  However, the IPCC view is also "Internal climate variability, by which we mean climate variability not forced by external agents, occurs on all time-scales from weeks to centuries and millennia. Slow climate components, such as the ocean, have particularly important roles on decadal and century time-scales because they integrate high-frequency weather variability  and interact with faster components. Thus the climate is capable of producing long time-scale internal variations of considerable magnitude without any external influences". Visbeck, Chassignet, Curry, Delworth, Dickson & Krahmann (2003) argue that while short-term variability of the NAO is determined by processes within the atmosphere,  the ocean's role is more important on longer timescales of  years and decades as changes in ocean circulation which are influenced by NAO variability take a long time to adjust. Thus the multi-decadal phases of the NAO may owe to the ocean's feedback on the NAO but there is no clear consensus on the mechanisms involved. This means that the decadal changes in the NAO which have occurred during the 20th century probably owe to changes in the ocean circulations (the thermo-haline circulation) and would therefore qualify as "long time-scale internal variations of considerable magnitude without any external influences" mentioned in the IPCC quote above. Assuming that changes in the NAO have significantly  contributed to global warming over the last 50 years, the underlying cause my be changes in ocean circulation.

COUPLED ocean-atmosphere models attempt to simulate natural internal variability like the NAO and they suggest that the trend to positive NAO since the 1960s has not made a significant contribution to recent global warming and that "most global warming over the last 50 years is from human activities". But in any field of science, to have confidence that a model is really modelling the system in question with accuracy, it is necessary to validate model predictions with real data. With respect to the climate, we have so little data (just annual values of global temperature comprise the main dataset for most model validation) and so there are no datasets which could be used to validate a model which attempted to produce values for the four climate feedbacks described above with respect to positive NAO winters.

THE theory articulated above that the warming/cooling/warming trend of global temperature record during the 20th century owes to changes in regional atmospheric circulations is plausible when you look at the number of regions in which annual temperatures are significantly correlated with regional atmospheric circulations. Climate models are not good enough to simulate changes in regional atmospheric circulation during the 20th century so they cannot be used to accept or reject this theory. This is a very important point because we have established that changes in regional atmospheric circulation dictate annual temperatures in a region but scientists claim that climate models which are unable to replicate such changes can predict global and regional temperature change during the 20th century. This is probably a case of the climate models getting the right answers via the wrong reasons. In weakness 1, it was shown that climate models show a linear relationship between atmospheric levels of carbon dioxide and global temperatures because of the values of greenhouse gas forcing given to the model by scientists. And the mid-20th century cooling period is explained by the models via the effects of sulphate aerosols which we know cannot possibly account for global cooling, only regional cooling at best. This is how climate models crudely replicate 20th century global & regional temperatures (this was discussed in weakness 3) but in the real world, these changes probably owe to a large degree to changes in regional atmospheric circulation.

IMPLICATION: the claim by scientists that global cooling during mid-20th century was caused by sulphate aerosols from coal-burning is seriously flawed and correlations between regional temperatures and regional atmospheric circulations clearly show internal climate variability to be the probable cause of this global cooling. The fact that scientists attribute both global warming and global cooling during the 20th century on the burning of fossil fuels and deny that internal natural climate variability had any major contribution to these events suggests they are biased in favour of man-made climate change.


7) THE EARTH'S CLIMATE IS NOT STABLE

THIS truth can be seen in regional instrumental and paleoclimate data (see weaknesses 4& 5) and we know from geological evidence that glaciers (mountain; sub-polar & polar) advance and retreat in response to regional climate change. There are many published papers which describe natural processes which cause climate changes: for example The early 20th century warming in the Arctic: a possible mechanism which shows how arctic temperature variability is largely caused by arctic sea ice extent which itself is vulnerable to large variability from decade to decade from changes in atmospheric circulation. Despite this wealth of evidence of continuous regional climate change and the indisputable fact that the Earth is comprised of regions, climate change scientists have attempted to construct a new orthodoxy that global temperatures were fairly static from 1000 to 1900 AD and only after 1900 have global temperatures shown any significant variability (Figure 1a). This new orthodoxy arose from the use of imperfect statistical techniques which attempted to combine the various regional paleoclimate datasets into one global dataset which could be viewed as a global temperature record. While combining the regional data into one global dataset was a logical development for extending our knowledge of global temperature changes, it has subsequently become evident from other paleoclimate reconstructions which show more variation (Figure 1b) that Mann et al (1999) seriously underrates temperature changes over the last millennium. Global temperatures over the the last millennium do not have a hockey-stick trend but the trend is basically one of two peaks with the left-hand peak representing the MWP and the right-hand peak representing 20th century warming. Now there is some uncertainty whether or not late 20th century global temperatures are higher than those of the MWP which is acknowledged in in Temperature Variations in Past Centuries and the so-called "Hockey Stick" but the current view is that they are and that only by considering increased greenhouse gas forcing can you account for this anomalous warmth.

CLIMATE model simulations of temperatures in the last millennium have also tended to reproduce a hockey-stick trend (Temperature Variations in Past Centuries and the so-called "Hockey Stick") but Stott, Jones & Mitchell (2002) have shown that most climate models underrate the effects of solar activity and this accounts for the hockey-stick trends. If models give greater weighting to solar activity, then the MWP & LIA are more pronounced (i.e greater millennial temperature variability) and the millennial temperature trend is one of two peaks with only late 20th century temperatures appearing anomalous.

THUS, in the cases of both paleoclimate and model reconstructions of millennial temperature variability, a tendency of some scientists to underrate temperature variability and the influence of solar activity has been identified through subsequent studies. This characteristic together with the fact that Mann et al (1999) overturned the orthodox view that the MWP was the warmest period of the last millennium and that 20th century temperatures were intermediate between those of the MWP & LIA strongly suggests that scientists may be biased in favour of man-made climate change and biased against natural factors and internal climate variability accounting for climate change. Jones & Mann (2004) even go so far as recommending that the terms MWP & LIA are no longer used by scientists as they think these terms "hamper rather than aid the description of past large-scale temperature changes". However, both the MWP & LIA are clearly visible in most paleoclimate reconstructions (Figure 1b) so to distinguish between these two periods in the last millennium by using specific jargon like MWP & LIA seems entirely logical. But the two most well-known scientists working in paleoclimatology would like the terms not to be used. Scientists are supposed to be unbiased and simply report on what they observe but it is clear that some climate change scientists are hostile to the idea that the MWP & LIA were periods of significantly warmer & colder temperatures respectively and have tried to show that until the 20th century, climate change was minimal and by doing so, it is necessary to invoke increased greenhouse gases as the cause of 20th century warming.

IN ADDITION to the MWP & LIA, evidence for significant climate change occurring naturally exists in the form of the geological evidence left by the Ice Ages when huge ice sheets several km thick covered land areas at high latitudes of the northern hemisphere and global temperatures were thought to be around 5 C colder than today. The causes of the ice ages are thought to be:

  1. atmospheric composition (particularly the fraction of CO2 and methane)
  2. changes in the Earth's orbit around the Sun known as Milankovitch cycles
  3. the arrangement of the continents with large areas of land at high latitudes of the northern hemisphere

THE reductions in insolation caused by the Milankovitch cycles are considered to be small and cannot account for the large changes in global temperatures which occur in an Ice Age but are considered to be a sort of trigger. This trigger then leads to positive feedbacks from growing ice and snow cover over northern hemisphere land masses and arctic sea ice which increase the Earth's albedo which reflects more incoming shortwave radiation back into space leading to further cooling and more snow and ice cover in the northern hemisphere. Reduced greenhouse gas concentrations are also thought to play a major role via a positive feedback process. Now an Ice Age is an extreme form of these climate feedbacks but surely it is quite plausible that the ice/snow albedo feedback has played a less dramatic but measurable role in the climate variations of the last millennium. The LIA is an obvious example of this effect although the principal causes of this are considered to be reduced solar activity and increased volcanism but reports from the time talk of icebergs in the North Atlantic, arctic sea ice extending south of Iceland, much heavier snowfall across high latitudes of the northern hemisphere giving more extensive and prolonged snowcover and snowlines were about 100m lower in both the northern and southern hemispheres than they were in 1975 (Wikipedia). Similarly, the global cooling of the 1950s, 1960s & early 1970s was associated with more arctic sea ice around Iceland and heavier and more widespread snowfall and snowcover across high latitudes of the northern hemisphere. So it is valid to pose the question, "to what extent did increased global albedo from increased ice and snow cover contribute to the global cooling of the LIA and the mid-20th century?". In the case of the LIA, the Moberg paleoclimate reconstruction in Figure 1b puts northern hemisphere temperatures at about 0.6 C below mid-20th century values around 1700 which is often considered to be the coldest period of the LIA whereas the 30 year running CET value for around 1700 (Figure 3) is a full 1 C below mid-20th century values. In the case of mid-20th century cooling, northern hemisphere temperatures fell around 0.3 C from a peak in the 1940s to the trough in the early 1970s (Figure 4). As we don't have satellite measurements of sea ice or northern hemisphere snowcover for either the LIA or mid-20th century cooling period, we can't even make a crude estimate about how much increased global albedo may have contributed to global cooling at these times but if this effect is powerful enough to cause ice ages, it is more than capable of making a contribution to 20th century global temperature changes (both warming and cooling) and the global temperature changes over the last millennium. Weakness 7 discussed mechanistic processes driven by positive NAO which may cause an increase in energy trapped in the Earth/atmosphere system (reduced outgoing longwave radiation and reduced global albedo) leading to global warming and negative NAO is likely to lead to global cooling via the opposite processes. This is a very plausible argument which MUST have made some contribution to global temperature changes in the last millennium and the 20th century but climate change scientists insist internal climate variability from all factors including changes in global albedo from changing sea ice and snow cover is minimal and that burning fossil fuels (sulphates) caused the mid-20th century global cooling and burning fossil fuels (greenhouse gases) caused the late 20th century global warming. Does this viewpoint look like another example of climate change scientists being biased in favour of man-made climate change and prejudiced against natural climate change?

IMPLICATION: we know very well from paleoclimate data, documentary data from the last millennium and geological evidence of ice ages that the Earth's climate is not stable but that it is inherently unstable and therefore it changes. Climate change scientists have attempted to argue that the Earth's climate is stable (at least over the last millennium) despite all this evidence and that it has suddenly changed during the 20th century to an unstable one because of the burning of fossil fuels. Now there has been some back-track from this viewpoint in recent years with the MWP & LIA being resurrected and a recognition that climate models underrate solar activity as a natural factor causing climate change. If scientists have underrated one natural factor (solar activity), might they not have underrated other natural factors such as changes in global albedo caused by changes in the NAO?

 

8) EVIDENCE THAT THE MEDIEVAL WARM PERIOD WAS WARMER THAN 20TH CENTURY EXISTS

PRIOR to attempts to combine the individual regional paleoclimate proxies into one global record (the first was Mann et al, 1998), the evidence of the individual regional paleoclimate proxies was the basis for the existence of the MWP & the LIA. A large number of papers support the existence of both the MWP & the LIA and Soon & Balunias (2003) used this wealth of published evidence in their paper and argued that as an assemblage of individual expert opinions on local climates, the paleoclimate records establish the existence of both the MWP & the LIA. The links below give a brief summary of some of these studies and show how in the opinion of the authors, the data suggest that temperatures were higher in the MWP than the current warm period:

SOON & BALUNIAS (2003) was widely cited outside the scientific arena as evidence that 20th century temperatures were not the warmest in the last millennium which is at variance with the IPCC view and therefore a rebuttal of Soon & Balunias (2003) was produced. This is On Past Temperatures and Anomalous Late-20th Century Warmth and three main points were articulated:

  1. the inclusion of studies which showed wet or dry climate anomalies as evidence of warmth in the MWP and cold in the LIA was a serious flaw in the methodology - this is true
  2. regional climate anomalies do not necessarily indicate a global or hemispheric anomaly and that the methodology of finding any warm 50-year period within a very broad interval of time such as AD 800-1300 does not indicate a synchronicity of such a warm spell around the globe
  3. the use of mean 20th century conditions as a benchmark for 20th century conditions was flawed because only late 20th century temperatures are considered anomalous in the context of the last millennium

POINT 1 is certainly valid but point 3 only has some validity because we know that many regional studies such as the examples listed above suggest temperatures in some regions were higher in the MWP than currently ie. late 20th century/early 21st century. Point 2 needs to be considered with respect to what causes a region to have its characteristic temperature regime. The three most important factors are probably:

  1. latitude & longitude ie. the location of a place on the Earth's surface in relation to the equator, the poles, continents and the oceans
  2. changes in regional atmospheric circulations eg ENSO, SOI, PDO, NAO etc
  3. changes in global temperature which will determine the overall background temperature of airstreams coming from all compass points

FOR the purposes of climate change over the last century or millennium, factor 1 is constant. Factor 2 is certainly very variable changing from year to year and from decade to decade and in a period as long as a few hundred years or a millennium which these paleoclimate studies cover, then there will be a number of periods (eg decades) which will be biased warm because of changes in regional atmospheric circulations. Factor 3 is certainly not as variable as factor 2 but is not fixed so will contribute to changes in temperature over a period of a few hundred years or a millennium. Therefore, the warmest period in a region within one millennium will be when the occurrence of regional atmospheric circulations favouring high temperatures coincides with high global temperatures. This is exactly the situation we have with the CET at the moment. The CET (Figure 3) commenced in 1659 and we know from paleoclimate reconstructions that northern hemisphere temperatures are higher now than at anytime since 1659 (Figure 1b), and we know that the NAO has favoured mild westerly winters (Figure 24) and warm anticyclonic summers (Figure 25) since 1988 and annual values, ten and thirty year running means show the CET to currently be at it's highest level on record (Figure 3). Assuming the same logic, all the regional paleoclimate studies covering most of the last millennium which show periods within the MWP warmer than recent decades must indicate higher global temperatures than today. Therefore there is strong evidence that for periods at least, global temperatures were higher during the MWP than they are today or at least similar.

WHILE the amalgamation of these regional temperature proxies into one global/northern hemisphere record is a logical development, if the result is at variance with the overall picture portrayed by the individual regional proxies, then the technique must be flawed. This appears to be the situation here and a number of papers as already mentioned have suggested that Mann et al (1998) & other reconstructions and climate model simulations underrate millennial temperature variability. If the process of perfecting these techniques is still not complete, then the current consensus that late 20th century temperatures are warmer than at any time in the last millennium may be overturned in due course. Imagine for a moment that the CET shown in Figure 3 extended all the way back to 1000 AD: from Figure 1b, we know that northern hemisphere temperatures from 1000 to 1500 AD were higher than in the LIA so the CET from 1000 to 1500 AD is likely to have been higher which is supported by documentary evidence but how much warmer would it have been and would it have been higher than post-1988 values? Pfister et al. (1998) in their study of winter temperatures from 750 to 1300 AD concluded that the warmest period was the 12th century which was comparable to 1961-90 conditions in Europe. On the other hand, to support the idea of a warmer climate than today, we have documentary data of wine growing in England and Winchester being named literally "Wine City". Jones & Mann (2004) suggest the idea of English wine growing in medieval times owes to a few monks producing wine for sacramental purposes and that wine growing has persisted in England throughout the millennium and the wine growing in the MWP doesn't reflect a more favourable climate. Well this is at variance with the consensus view that wine growing was more widespread in England during the MWP than during the LIA because of a warmer climate. And there are a number of paleoclimate studies for Europe which suggest temperatures in the MWP were warmer than late 20th century temperatures:

IMPLICATION: judging by the evidence from individual regional paleoclimate records, globally periods within the MWP probably were warmer than late 20th century temperatures.


9) SCIENTISTS CAN'T AGREE ON THE RATE OF GLOBAL WARMING OF THE LAST FEW DECADES AND HOW UNUSUAL IS IT?

GLOBAL temperatures are currently measured using data from thermometers on land (the surface temperature record) and from measurements of temperatures in the trophosphere made by radiosonde balloons and satellites (via Microwave Sounding Units (MSU)). The MSU data have caused most controversy because two different research groups using different analytical techniques produced global warming trends which were significantly different: the University of Alabama (UAH) team, Christy & Spencer, who pioneered the use of  MSU data as a measure of global temperature found a warming trend of 0.09 k/decade since 1979 for their MSU2LT product whereas the Remote Sensing Systems (RSS) team, Mears & Wentz, found a significantly higher global warming trend of 0.19 k/decade.   The surface temperature record shows a global warming trend of 0.2 k/decade, similar to the RSS team. This disagreement has not inspired confidence in the science of climate change and sceptics have used the lower warming trend of the UAH team to challenge the alarmist view of the IPCC about global warming. An excellent but long review of this issue can be found here. Since this review was written in February 2005, errors have been identified in the UAH methodology which has increased the decadal warming trend from 0.09 k/decade to 0.12 k/decade which brings it closer to the RSS warming trend of 0.19 k/decade and surface warming trend of 0.20 k/decade. A number of recent articles on this issue are linked to below:

IT is certainly good news that there is less disagreement between the UAH & RSS MSU products but there is still a difference of 0.07 k/decade. And even if we accept the RSS and surface temperature global warming trends of 0.19-0.20 k/decade being accurate, is this a reason for panic like the IPCC argues and unambiguous proof of man-made climate change? Compared with year to year variations in global temperature caused by natural fluctuations, this decadal warming trend is not large. For example, the 1997-1998 El Nino caused a rise in surface global temperature of 0.4 C from 1996 to 1998 and a rise in lower trophosphere temperatures of 0.8 C (Figure 27).  And large volcanic eruptions which eject sulphates into the stratosphere cause a reduction of global surface temperature of ~0.3 C for two or three years after the eruption (Volcanoes and their effect on climate) and in the largest eruptions like Tambora in 1815, this global cooling effect could have been as large as 1 C. And the more recent millennial paleoclimate reconstructions such as Moberg et al (2004) in Figure 1b which shows global temperatures in the coldest period of the LIA   0.7 C colder than 1961-90 values suggest that decadal warming/cooling trends of 0.1 to 0.2 k/decade are not unprecedented and can be explained by natural factors. In fact, global temperatures were rising at the rate of 0.1-0.2 k/decade in the 1930s & 1940s (Figure33). So a global warming trend of 0.2 k/decade is not proof of man-made climate change and is not a reason for panic.

Figure 33  Annual values of GHCN Global Surface Temperature Anomalies (from 1961-90 averages) 1880 to 2003 compared with ten and thirty year running means of annual values.

FOR sure, if this rate of increase in global temperature were to persist for ten decades, then the Earth would warm by a full 2 C which would be much higher than the 20th century global warming of ~ 0.7 C but we don't know that it will persist. Indeed the rate of global warming has slowed in the last few years. Figure 34 shows that since 2001, both the surface temperature record and the UAH MSU data have stabilised somewhat showing no real tendency to increase or decrease and both records are still comfortably below the peak in 1998 caused by the strong El Nino at that time. Figure 34 also presents some natural factors to test the hypothesis that natural factors and not man-made sources of greenhouse gases are the overriding factors dictating global temperature changes. El Ninos occur when SOI is negative and the 1997/1998 El Nino was unusually intense (i.e very negative SOI) and resulted in 1998 being the warmest year on record. During 1998, the SOI turned positive and PDO turned negative, both of these factors favouring lower global temperatures. At the same time, sunspot numbers were increasing to reach a solar maximum from 1999 to 2002 which favours higher global temperatures. Global temperatures did indeed fall from 1998 until the end of 2000 as suggested by the positive SOI & negative PDO but the sunspot maximum may have resulted in global temperatures staying well above the long term average.

 



                       EL NINO                        DECREASING PDO & SUNSPOT MAXIMUM                     EL NINO

Figure 34  Monthly values of GHCN Global Surface Temperature anomalies, Christy & Spencer analysis of MSU lower atmosphere temperature anomalies(LT5.2), Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO) and sunspot counts January 1997 to May 2006.

SOI turned negative again in 2002 as the 2002/2003 El Nino event developed and PDO turned positive, both favouring higher global temperatures and this situation has not changed since then as weak El Nino conditions have mainly persisted since 2003. Sunspots have been decreasing as the sunspot minimum in 2007/2008 approaches and this may have somewhat counteracted the global warming effects of negative SOI in recent years so that global temperatures have been rather stable. Eventually, positive SOI and negative PDO will return and assuming this happens prior to the next sunspot peak which is likely to be the case,  global temperatures should fall according to the natural factors theory. Figure 34  is updated each month to see if the temperature data support the natural factors theory by falling or whether the temperatures continue to rise as predicted by the IPCC owing to more greenhouse gases in the atmosphere.

DISCUSSION

THE scientific method is where scientists observe something and then develop a hypothesis to explain the observation. In the case of climate change, scientists have observed that the globe has warmed and have suggested the hypothesis that increased atmospheric levels of carbon dioxide from fossil fuel burning have increased the Earth's greenhouse effect thereby causing the increased global temperature. An essential part of the scientific method is that the hypothesis must be tested by making predictions to prove that it is a robust and cogent hypothesis. This is where the climate models play an important role and in this case, support the hypothesis but we also know that climate change occurs naturally (because of lots of evidence of the MWP, the LIA & Ice Ages) which proves the existence of alternative causes of climate change. A robust and cogent hypothesis would enable scientists to exclude the possibility that such alternative causes of climate change don't apply in this case. If the hypothesis fails to demonstrate that it is better than alternative explanations of recent global warming, then the scientific method demands it be rejected.  However, once it has been established that a hypothesis is sound (by use of the above methods), it becomes a theory.

SO what is the situation with man-made global warming? Is the hypothesis robust and cogent enough to reject the argument that natural factors have caused recent global warming (situation A) or might natural factors account for recent global warming meaning the man-made global warming hypothesis should be rejected (situation B).

THE IPCC Third Assessment Report  says situation A applies and that man-made climate change is certain and that "most global warming over the last 50 years is from human activities". The next section argues that situation B applies by combining the nine weaknesses discussed above into two main criticisms:

1) SCIENTISTS ARE MAKING EMPHATIC CLAIMS ABOUT THE EXISTENCE OF MAN-MADE CLIMATE CHANGE WHICH GO WAY BEYOND WHAT THE DATA ALLOW: weakness 1 does mention a paper which shows that increased greenhouse gas forcing is occurring as greenhouse gas concentrations in the atmosphere rise. Therefore it is logical to accept that this increased greenhouse gas forcing has made a contribution to global warming over the last 50 years but do the data permit the IPCC to go as far as "most" global warming? Detecting & Attributing External Influences on the Climate System: A review of Recent Advances says recent research strengthens the IPCC Third Assessment Report conclusion that "most global warming over the last 50 years is likely due to the increase in greenhouse gases" and "Myth versus Fact regarding the 'Hockey Stick'" describes Detection & Attribution Studies as perhaps the strongest piece of evidence of man-made climate change. But weakness 3 pointed out that these studies are just another name for climate model studies and weakness 1 pointed out that climate models grossly simplify the atmosphere and climate by treating the atmosphere as a mere container for greenhouse gases and reducing climate change merely to a changed balance of incoming and outgoing radiation dictated by greenhouse gases. The atmosphere and climate change are both more complex than these simplistic representations. And weakness 3 identified that Detection & Attribution Studies of type 1 depended on sulphates from coal-burning to explain the mid-20th century global cooling which cannot possibly be the real explanation (weakness 6) while studies of type 2 depend on millennial temperatures having a hockey-stick shaped trend implying 20th century temperatures are unusual when climate change scientists acknowledge that only late 20th century temperatures are unusual meaning millennial temperatures have two peaks, the left peak being the MWP and the slightly higher right peak being the 20th century.

PERHAPS the most obvious example of scientists going way beyond what the data allow is the claim that global temperatures are higher now than at anytime in at least one thousand years. This claim is based on paleoclimate reconstructions and the uncertainty of these was discussed in weakness 2. The evidence for periods within the MWP being warmer than today was mentioned in weakness 7 and a number of publications which state that the recent warmth in Europe is within natural variability of the last 600 years which included much of the LIA were cited in weakness 4. And the seasonality of the warming of the CET since the 18th & 19th centuries (the latter part of the LIA) which  shows that temperatures in five months of the year have not warmed significantly (weakness 5)  seriously challenges this claim about global temperatures being exceptionally high and at their highest for over a thousand years.  The evidence from Europe and central England is that the magnitude of global warming during the 20th century isn't that large although global warming has certainly occurred. But scientists are going way over the top and exaggerating the magnitude of global warming.

2) SCIENTISTS ARE BIASED IN FAVOUR OF MAN-MADE CLIMATE CHANGE & BIASED AGAINST NATURAL FACTORS AS CAUSES OF CLIMATE CHANGE

A number of examples of this were mentioned in weaknesses 1 to 9 and these are summarised below:

  1. Mann et al (1999) shown in Figure 1a overturned the orthodox view that there had been ~2 C global temperature change over the last millennium being warmest at the beginning (the MWP), coldest in the middle (the LIA) and 20th century temperatures were somewhere in between and argued that there had been so little temperature variation that the MWP & LIA were not valid concepts and that 20th century temperatures were much warmer than previous centuries. However, more recent reconstructions (Figure 1b) have restored the MWP & LIA to a large degree and other scientists have suggested that the Mann et al (1999) may underrate millennial temperature variability (weakness 2)
  2. climate models underrate the effects of solar variability on climate (Stott, Jones & Mitchell, 2002)
  3. the argument that mid-20th century global cooling was caused by sulphates from coal burning is seriously flawed and it beggars belief that scientists advocate it as the cause (weakness 6)
  4. highly significant relationships between regional atmospheric circulations and regional temperature records around the northern hemisphere strongly suggest that cold weather patterns caused mid 20th century global cooling and that there is a relationship between global weather patterns and global temperature (weakness 6) but while ENSO/SOI is acknowledged as a major factor in the warmest year on record (1998), scientists appear to deny that a higher incidence of El Ninos in the last few decades or changes in other  regional atmospheric circulation have made a significant contribution to global warming over the last 50 years
  5. the NAO is a regional atmospheric circulation which scientists acknowledge accounts for much of the year to year variability in northern hemisphere temperature (Hurrell, 2003) but scientists appear to deny that it could have made any significant contribution to global warming over the last 50 years despite a marked long term increase in the winter NAO since the 1960s (Figure 32)
  6. historical data from the LIA and the mid-20th century global cooling show that negative winter NAO prevailed at these times and that northern hemisphere sea ice and snow cover increased which suggests that changes in the NAO may cause a positive feedback via changes in global albedo from changing sea ice & snow cover extent which may alter global temperature. This feedback is acknowledged as an important factor in the development of Ice Ages but scientists appear to deny that it has played a significant role in either the LIA or changes in global temperature during the 20th century including the mid-century cooling (weakness 6)
  7. scientists have tried to argue that the Earth's climate is naturally stable (Figure 1a) despite a wealth of evidence of climate instability in the form of the MWP, the LIA and Ice Ages (weakness 7)
  8. as we know that the Earth's climate changes naturally, then the observed rate of global warming over the last two decades of ~0.2 k/decade (weakness 9)  is not clear evidence of man-made climate change but may owe to natural factors or to a combination of natural & anthropogenic factors. Yet, the IPCC view is that MOST global warming over the last 50 years is due to human activities.

FACTORS other than changed greenhouse gas forcing may alter the global temperature but the IPCC insists over the last 50 years, increased greenhouse gas forcing accounts for most (i.e nearly all) global warming which means other factors account for little global warming. This is a very biased view when scientists acknowledge that El Ninos cause short-term global warming and these have been more frequent in recent decades and acknowledge that the NAO accounts for much of the year to year northern hemisphere temperature variability and there has been a long term increase in the NAO since the 1960s which has favoured higher northern hemisphere temperatures. The relationships between regional atmospheric circulation and regional temperature 1900-2001 shown in weakness 6 clearly indicate that changes in global weather patterns have dictated the warming/cooling/warming trends of the 20th century.  Therefore internal climate variability is a significant factor in recent global warming but scientists deny this and insist that the atmosphere is just a mere container for greenhouse gases (weakness 1) and the only factor of any significance in the last 50 years is increased greenhouse gas forcing.

IN CONCLUSION, this article disagrees with the view of the IPCC that most global warming over the last 5o years is from increased greenhouse gases and it identifies nine weaknesses in the science which some scientists are overlooking because they are willing to go way beyond what the data allows in their claims about man-made climate change and are biased in favour of man-made climate change and biased against natural factors as causes of climate change. Climate does change naturally and our ancestors have provided us with plenty of evidence of this over the last 1000 years, particularly for the UK & Europe where recent warming is within natural variability. Yet the IPCC insists that the climate changes over the last 50 years, both global warming and global cooling owe to the burning of fossil fuels and couldn't possibly be natural but they do acknowledge that internal variability from atmospheric-oceanic processes does lead to significant climate variability, particularly over longer time scales of decades and centuries (Climate Change 2001: the Scientific basis) but scientists claim that this is not the case over the last 50 years. Their argument that internal climate variability hasn't contributed to changes in global temperature during the 20th century is nonsensical and is contradicted by the relationships between regional atmospheric circulation and regional temperature 1900-2001 shown in weakness 6. The conclusion that "most global warming over the last 50 years is from human activities" conflicts with the modelling study of Zorita et al (2004) which shows that the magnitude of 20th century global warming was similar to natural rebounds of global temperature  in the LIA. The magnitude of current global warming is the same as that which occurred in the 1930s & 1940s and other historical data and some modelling studies suggest this rate of global warming is not unusual. All this panic and hysteria and paranoia that scientists are inciting is not only unconstructive but is completely irrational when our ancestors have left us evidence that climate change is a natural phenomenon. It is quite likely that increased greenhouse gases have made a contribution to 20th century global warming but the IPCC view that most global warming  over the last 50 years is caused by increases  in the greenhouse effect appears a biased view. There is no doubt that reducing greenhouse gas emissions from the burning of fossil fuels is a good long term objective and this message has certainly sunk in with even the energy industries playing a willing role in reducing greenhouse gas emissions. However,  it will probably take a couple of decades for the UK to generate just 25% of its electricity from renewables but the  IPCC says that the only way we can avoid catastrophic global warming is by making dramatic cuts in greenhouse gas emissions now. Owing to the importance of fossil fuels to our way of life and all the wonderful benefits fossil fuels bring us all, it is unlikely that dramatic global cuts in greenhouse gases will occur within the next 20 years. And this article argues that it is unlikely that the extremely pessimistic climate predictions of the IPCC will come true because the IPCC is exaggerating the evidence for man-made climate change and re-branding natural climate change as man-made.

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