Temperatures in the first half of 2004 and a few observations on the rate of Global Warming

By Andrew Masterman 31 July 2004

Here are some temperature data for the first six months of 2004 for the UK, Europe and the Globe. In summary, in all three cases, temperatures so far this year are well above the long term averages although not the warmest on record.

UK

The mean Central England Temperature (CET) for January to June 2004 is 9.10 C which is 1.35 C above the 1961-90 average. There have only been three years with warmer January to June periods since 1900 and 1992 was equally warm as 2004:

1990: 9.38 C; 1998: 9.23 C; 2002: 9.25 C.

EUROPE

The mean European temperature anomaly for January to June 2004 calculated by averaging the data from the ten stations presented in Table 1 is 0.8 C above the 1961-90 average (comparative data in 2002: +2.0 C; 2003: +1.2 C). Table 1 clearly shows that averaged across Europe, temperatures have been above average in all the first six months of 2003 although positive anomalies have not been large apart from February in Wroclaw (+3.0 C) and June in Valladolid (+3.8 C).

Table 1 Anomalies of mean monthly temperature January to June 2004 across Europe relative to 1961-90 averages.

	Mean monthly temperature anomalies relative to 1961-90 averages C
	___________________________________________________
	Jan	Feb	Mar	Apr	May	Jun	Mean Jan-Jun
___________________________________________________________________
Valentia, Ireland	+0.9	+0.5	+1.0	+0.7	-	-	-
Aberdeen, UK	+1.2	+1.2	+1.0	+2.1	+1.8	+1.4	+1.5
Nantes, France	+1.7	0.0	-0.5	+0.5	+0.8	+1.9	+0.7
Valladolid , Spain	+1.5	-0.3	-0.5	-0. 2	+0.3	+3.8	+0.8
De Bilt , Netherlands	+1.5	+ 2 .3	+1.0	+ 2 .5	+0.1	+0.4	+1.3
Geneva , Switzerland	+ 2 .0	+1. 2	+0.4	+1.9	-	+1.4	+1.4*
Wien , Austria	-0.6	+ 2 .1	-0.7	+1.5	-1.4	+0. 2	+0. 2
Helsinki , Sweden	-0.1	+1.9	+1.6	+1.8	-	-1.8	+0.7*
Wroclaw , Poland	-0.6	+3.0	+1. 2	+1.4	-	+0.4	+1.1*
Athens , Greece	-0.6	+0.3	+1.0	+0.5	-0.1	+1.5	+0.4

Europe Mean	+0.5	+1. 2	+0.6	+1.3	+0.3	+1.0	+0.8**
____________________________________________________________________

* average of 5 months ** mean of six monthly Europe means

GLOBE

The official prediction for global surface temperatures in 2004 is: 'The global prediction for 2004 is for 0.50 °C +/- 0.12 °C above the 1961-1990 average, with a 95% confidence range of 0.38 °C to 0.62 °C. This best estimate forecast would place 2004 as the second warmest year on record. There is about a 20% probability that 2004 will be as warm as or warmer than the warmest year on record, 1998 which was 0.55 °C.' (from bottom of this UK Met Office article).

Table 2 shows the monthly anomalies of global temperatures in the first six months of 2004 and compares global temperatures in the first half of 2004 with those in 2002 & 2003. Certainly a very warm first half of 2004 which is in line with the prediction above but all three global temperature records show lower values in May and June.

Table 2 Monthly Global Temperature anomalies January to June 2004: Land & Ocean Surface temperature records (CRU & GHCN) and satellite measurements of the temperature of the lower atmosphere (Christy & Spencer data)

	Global Temperature Anomaly C


	CRU	GHCN	Satellite
	_______	_______	________
_________________________________________________________
January 2004	+0.455	+0.54	+0.282
February 2004	+0.616	+0.62	+0.284
March 2004	+0.505	+0.70	+0.327
April 2004	+0.457	+0.52	+0.127
May 2004	+0.283	+0.38	-0.001
June 2004	+0.354	+0.47	-0.021

2002	+0.562	+0.657	+0.267

2003	+0.437	+0.545	+0.171

2 004	+0.445	+0.538	+0.166
_______________________________________________________

Below are two unofficial predictions of global temperatures in 2004 using multiple regression models described in Multiple Regression Modelling of Global Surface Temperature Record and Satellite Temperature Record. They are in line with observed global temperature data as is the official prediction.

Multiple Regression Prediction of Global Surface Temperature in 2004 is 0.42 C above 1961-90 average
Dec 2003 to May 2004 Southern Oscillation Index: -0.1
Jan to Apr 2004 Pacific Decadal Oscillation: +2.09
Estimated 12 year running mean of annual sunspot counts: 60.9. ( mean monthly number Jan-Jun 2004 is 42.7)
Estimated atmospheric CO₂ cconcentration for 2003: 381 ppm (378 ppm observed in late 2003).

Multiple Regression Prediction of Global Satellite Temperature of Atmosphere in 2004 is 0.149 C above 1979-98 average.
Jan to May 2004 Southern Oscillation Index: -1.2
Jan to Mar 2004 Pacific Decadal Oscillation: +1.52
Estimated annual sunspot counts: 42.7( mean monthly number Jan-Jun 2004 is 42.7)
Estimated atmospheric CO₂ concentration for 2004: 381 ppm (378 ppm observed in late 2003).

A few observations on the rate of Global Warming

Figure 1 shows the familiar graph of rising global surface temperatures which clearly indicates that annual values in the last ten years are unequivocally the warmest on record. The rise in the ten year running mean from 1900 to 2000 was 0.51 C and over the last ten years (1994-2003) 0.18 C. So the rate of warming in the ten year running mean over the last ten years is almost four times the average rate of the twentieth century as a whole. The range of IPCC predictions for the twenty first century is 1.4 to 5.8 C so the observed warming over the last ten years is at the lower end of this range but it should be noted that the IPCC predictions show much greater rises after 2050.

Figure 1 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.

Focussing on the global temperature data of the last ten years, Figure 2 presents monthly anomalies of GHCN global surface temperature anomalies form January 1995 to June 2004 (almost ten years): 12 month running means have increased from 0.41 C to 0.56 C, a rise of 0.15 C, equivalent of 1.5 C per century or three times the observed rate over the twentieth century as a whole.

Figure 2 Monthly values of GHCN Global Surface Temperature Anomalies (from 1961-90 averages) January 1995 to June 2004 (9.5 years) compared with 12 month running means of monthly values.

However, over the last three years, global temperatures have stabilised to some extent at between 0.5 to 0.6 C above the 1961-90 averages, showing no tendency beyond a month or two of either warming or cooling. It remains to be seen whether the cooler global temperatures observed in May and June 2004 are a minor aberration or the start of a cooling trend of some sort. It is well known that climate is cyclical and Figure 2 with hindsight may show the peak in a cycle of global temperatures assuming that global temperatures continue the cooling trend of the last few months. Regardless of what global temperatures do from now on, recent months highlight the magnitude of natural variability in global temperatures: the drop of 0.3 C in mean global surface temperature from March 2004 to May 2004 is 66% of the value of the rise in the ten year running mean in annual values of global temperature from 1900 to 2000: 0.5 C (Figure 1). Although such a change in monthly anomaly over two months is not equivalent to a change in the ten year running mean of the same value, it does highlight the magnitude of natural variability and therefore calls into question the claim that the global warming of 0.6 C over the twentieth century is so earth-shattering and significant and couldn't possibly be natural. Natural variability is being underrated in the Man-made climate change debate and it is possible that it could account for most of the global warming over the last few decades. But the official IPCC line is 'most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.'