CSIRO - View on Temperature Trends
unpublished letter sent to CSIRO Chief Research Officer Paul Fraser, 28 July 2010
Dr Paul Fraser
Chief Research Officer
CSIRO
28 July 2010
Paul
Thank you for responding to my message of 14 July by forwarding a paper written by two of your colleagues on the question of temperature trends, with particular reference to what has happened in recent years. You suggest that it explains much better than you could about global temperature trends.
Their conclusion is certainly quite clear - that “there is very little justification for asserting that global warming has gone away over the past ten years”. As I understand it, their view is that temperatures changes must be assessed by calculating underlying linear trends over periods of at least ten years and that appear to be calculated after adjusting for one-off influences, such as from volcanoes, El Ninos, and “different effects of day-to-day and week-to-week fluctuations in the weather”. Their graphical presentations include the period back from 2007 to 1910 (and even to 1850) as well as the period from 1998 to 2007. For the latter their linear trend shows a very slight warming trend; for the longer periods they appear to show global temperatures increasing from 1910 to the early 1940s, followed by a slight cooling to the mid to late 1970s, then a marked increase to 1998.
In my email to you on 14 July I said that there was “no questioning by me that concentrations of greenhouse gases and global temperatures have increased over the past 100 years or so (although one would have to say that there seem to be serious questions about whether the method of measuring temperatures has overstated the rise, including in Australia). But the increase in concentrations over the same period as temperatures rose does not establish a cause and effect relationship”. Those comments still stand.
To take this aspect a little further, while nobody doubts that there has been a warming trend since the depths of the Little Ice Age during the 1600s, this commenced well before anthropogenic emissions began to increase rapidly after World War 11 and we do not know what caused that underlying trend. Taking the last decade and a half, we also know that while CO2 concentrations have continued to rise, temperatures have formed a plateau, or even on your colleagues’ calculations, an increase much lower than might be expected given the dangerous warming thesis.
Indeed, if we projected forward the linear trend for the period 1998 -2007, then using the HadCRUT3 calculation by your colleagues in Figure 2 it looks as though one would get an increase in temperature of about 0.5 of a degree by 2100. My statistician colleague has in fact calculated that the linear regression for the HadCRUT data has a slope of 0.05 +/- 0.10 0C per 10 years ie over 100 years the projected temperature rise is 0.5 +/- 1.0 0C. This means there is in fact no statistically significant temperature rise in the last 9 years because the error margin is larger than the temperature increase from the linear fit.
Without access to the detail of your colleagues’ calculations, it is not possible to reach a definitive view on their trend analysis over longer periods. I do observe that, while they have adjusted temperature data to remove what they describe as the “marked effect on global temperatures” from the El Nino-Southern Oscillation, no adjustment seems to have been made for the major determining influence on the surface temperatures from the Pacific Decadel and the Atlantic Multi-decadel oscillations. Nor it seems have any adjustments been made for the major warming effect from the Great Pacific Climate shift in the mid 1970s. Further, a colleague of mine has pointed out that no account seems to have been taken of the recent analysis by Wang and Dong (in Geophysical Research Letters, Vol. 37) suggesting that the Atlantic Multi-decadel oscillation changed phase in the late 1990s and thereby contributed to the subsequent plateau in temperature.
I should mention that I have also received an email from another of your colleagues, who appears to have seen our exchanges. His assessment is that “there was about as much warming in the period 1900 to 1950, when computer models agree that man made contributions were negligible (IPCC Ch 9, p703, FAQ9.2, Fig.1), as in the period of 1950 to 2000, when man-made additions of CO2 to the atmosphere have been increasingly large”. His assessment of recent years is that they “illustrate your point that recent 5 year averages show some recent cooling although 10 year averages generally show warming”.
Also relevant is that your colleagues’ paper is dated April 2008, after which the Climategate issue in November 2009 raised serious questions about the accuracy of published temperature data.
Perhaps they would regard those questions as being dismissed by the exonerations given by the Muir Russell and Oxburgh inquiries. However, although those inquiries “cleared” Professor Phil Jones, head of the Climate Research Unit at East Anglia, reactions to the inquiries make it apparent that they have not improved the confidence of independent analysts in the data and analyses by the scientists involved: rather the opposite. I see that even the US Department of the Environment has suspended the financial contributions it was making to the CRU pending further examination of the matter.
Even so, because Jones (and the CRU) appear to have been key contributors to the data and analyses contained in IPCC reports, his views are relevant when considering the temperature analysis by your colleagues. In an interview he gave on the BBC in February 2010 (the transcript of which I have), Jones agreed with the BBC’s environmental analyst that there has been no statistically-significant global warming since 1995. He also agreed that the trend from January 2002 to “the present” (ie Feb 2010) was slightly negative (but again not statistically significant), that analysts have “different ways” of assessing the quality of temperature data, and that the Met Office needed to release more “station” data. I note also that Jones said that he judged the vast majority of scientists did not believe the debate on climate change is over and that “there is still much that needs to be undertaken to reduce uncertainties”.
I hope that, with the previous material I have sent you, the foregoing might encourage you and your colleagues to review thinking at CSIRO on the global warming issue.
Regards
Des Moore