PREDICTIONS OF FUTURE WARMING IN THE UK
AS already discussed, there is scientific
uncertainty as to whether the earth is currently warming as depicted by the
surface temperature record owing to higher concentrations of
carbon dioxide (CO2).
Future warming is a separate issue and the
UK Climate
Impacts program has published new predictions in 2002
(UKCIP02) for the UK climate in
the next 100 years. There are four different climate change scenarios defined by
the predicted atmospheric concentration of CO2 in parts per million (ppm)
in the period 2071 to 2100: low emissions 525 ppm; medium low emissions 562 ppm;
medium high emissions 715 ppm; high emissions 810 ppm.
Atmospheric
concentrations of CO2 have been measured since 1958 (first in
California and subsequently at Mauna Loa, Hawaii since 1974 data here) showing a rise of 54 ppm from
316 in 1958 to 370 in 2001. The annual rate of increase in
California was 0.9 ppm per year while at Mauna Loa, it is 1.53 ppm per year with
no sign of any increasing trend. A similar increase has
also been measured at the
South Pole.
At 1.53 ppm per year, an atmospheric
concentration of 521 ppm would be reached in 2100 suggesting that the higher three scenarios are much more pessimistic than current observations of atmospheric CO2 would suggest.
Greenhouse gases and
aerosols discusses CO2 measurements and shows that half of the extra CO2
emitted from burning fossil fuels which enters the atmosphere is being absorbed
by the land and oceans rather than building up at alarming rates in the
atmosphere as predicted by the greenhouse scientists.
UKCIPO2 predicts a warming in the UK of 2oC for the low emissions scenario and 3.5oC for the high emissions scenario with greater warming in the summer and autumn than the winter and spring. In contrast, CET observations from 1991 to 1999 which have been 0.57oC above the 1961-90 average annual figure of 9.47oC have shown most warming in the
winter (Dec-Feb) and spring (Mar-May) (0.72oC) rather than summer (Jun-Aug) and autumn (Sep-Nov)(0.42oC).
CET summer graph clearly shows that with the exception of 1995, summer temperatures of the 1990s were not exceptionally high in the context of the 342 year record. In contrast, the other
three seasons showed clear and remarkable warming trends. Whether this means the warming of the UK in the 1990s is unrelated to increasing greenhouse gas concentrations, or the UKCIPO2 predictions are wrong or both only time will tell!
UKCIPO2 also predicts higher rainfall in winter but less in summer. While
the 1990s in Britain were undoubtedly warm, there was no consistent pattern in seasonal rainfall with some notable dry & wet periods in the early and
mid 1990s but a tendency for wetter than average years more recently.
Winter &
summer
EWR
from 1985 to 2002 shows large variations between years relative the 1961-90
averages but overall for both winter and summer there is no bias to high or
low rainfall (Table 2).
Table 2 showing winter & summer England & Wales rainfall
1985-2002 allocated to low, average* and high rainfall categories
| Season |
Low |
Average* |
High |
| Winter |
5 |
7 |
6 |
| Summer |
6 |
5 |
7 |
* percentages of average 1961-90 rainfall between 90 & 110 inclusive.
EWR is rainfall averaged over England & Wales and can hide regional
variations which may be large. Regional rainfall datasets have been constructed for the UK
by the CRU using data going back to
1931. These data for five regions of England & Wales, three in Scotland &
for Northern Ireland have been published (Gregory, Jones & Wigley (1991) & Wigley & Jones (1987)) and can be studied to assess how regional rainfall has changed since 1931.
Gregory, Jones & Wigley (1991) reported that data from 1931-89 showed no
long-term trends.
UKCIPO2 offers both a full report and a briefing report which can be downloaded as
pdf files
and a wide range of
maps
online showing how various weather variables are expected to change in
different regions of the UK and under the four different scenarios. All in
all a very interesting and information rich website about
UK weather and climate predictions.
FLOODING in eastern europe in August 2002 has renewed speculation that increasing atmospheric CO2 concentrations/global warming are changing the world's climate. In this case, climate experts have been stating that natural variability in the position of the jet stream is the likely explanation for this weather and not global warming (BBC article BBC Weather article UK Met Office). The reason for this is that lower summer rainfall is predicted for the UK and Europe by climate change scientists. Indeed, the UKCIPO2 are quite alarmist in the extent to which they predict lower summer rainfall for Britain. For example, in the most optimistic low emissions scenario, England is predicted to have 10-20% less summer rainfall than the 1961-90 average by the 2020s (30 year period 2011-2040). This rises to an alarming decrease of more than 50% summer rainfall by the 2080s (30 year period 2071-2100) in the high emissions scenario. With frequent rain being a characteristic of summer 2002 in Britain (see BBC UK Weather Year So Far for weather statistics) and no trend to drier than average summers apparent in the summer rainfall data of 1985-2001, scepticism about global warming/climate change is grounded on real weather observations unlike the alarmist climate predictions which are based on computer models. Global warming/climate change sceptics also attribute all weather events to natural variability whereas climate change scientists attribute some events (eg flooding in eastern europe in 2002) to natural variability while others to climate change/global warming (eg the warmth of the 1990s in Britain) according to whether or not such events are consistent with their computer model predictions.
REFERENCES
Gregory, J.M, Jones, P. D. & Wigley, T. M. L. (1991). Precipitation in Britain: An analysis of area-average data updated to 1989. Journal of Climatology, 11, 331-345
Wigley, T. M. L. & Jones, P. D. (1987). England & Wales precipitation: a discussion of recent changes in variability and an update to 1985. Journal of Climatology, 7, 231-246.
