Contrary to claims being made by the leader of the Best global temperature initiative their data confirms, and places on a firmer statistical basis, the global temperature standstill of the past ten years as seen by other groups.
Many people have now had some time to read the papers issued in preprint form from the Best project. My strong impression is that they are mostly poorly written, badly argued and at this stage unfit for submission to a major journal. Whilst I have made some comments about Best’s PR and data release strategy, I want to now look at some aspects of the data.
When asked by the BBC’s Today programme Professor Richard Muller, leader of the initiative, said that the global temperature standstill of the past decade was not present in their data.
“In our data, which is only on the land we see no evidence of it having slowed down. Now the evidence which shows that it has been stopped is a combination of land and ocean data. The oceans do not heat as much as the land because it absorbs more of the heat and when the data are combined with the land data then the other groups have shown that when it does seem to be leveling off. We have not seen that in the land data.”
My first though would be that it would be remarkable if it was. The global temperature standstill of the past decade is obvious in HadCrut3 data which is a combination of land and sea surface data. Best is only land data from nearly 40,000 weather stations. Professor Muller says they “really get a good coverage of the globe.” The land is expected to have a fast response to the warming of the lower atmosphere caused by greenhouse gas forcing, unlike the oceans with their high thermal capacity and their decadal timescales for heating and cooling, though not forgetting the ENSO and la Nina.
Fig 1 shows the past ten years plotted from the monthly data from Best’s archives. Click on the image to enlarge.
It is a statistically perfect straight line of zero gradient. Indeed, most of the largest variations in it can be attributed to ENSO and la Nina effects. It is impossible to reconcile this with Professor Muller’s statement. Could it really be the case that Professor Muller has not looked at the data in an appropriate way to see the last ten years clearly?
Incidently you could extend the graph back a few years before 2001 and it doesn’t make much difference because the ‘super el nino’ of 1998 and the two subsequent cooler years of 1999 and 2000 do not show up as dramatically in the Best land data as they do in HadCrut3. However, this still means that if you start the graph in 2000 or 1999 you are cherry-picking cooler years for a start point that would produce a bias. I maintain that if you extend it back you must include the El Nino and La Nina years as they are not independent. I would also caution against the indiscriminate use of trendlines. I would also point out that there is now an abundance of peer-reviewed literature that deals with the question of the lack of temperature increase in the past decade, so our graph’s starting point and duration is justifiable. Wether the last two points should be included is debatable as they are polar only data with a high uncertainty. Arguments that the time period we chose was cherry-picked to show a flat line, and that slightly longer periods would not, are incorrect. There are, of course, still those who distort the argument by saying that ten years is too short for climatic conclusions, as if ten years of data is meaningless. Also Professor Muller was asked a specific question about the last ten years, and our graph is a response to his specific answer.
Indeed Best seems to have worked hard to obscure the past decade. They present data covering more almost 200 years is presented with a short x-axis and a stretched y-axis to accentuate the increase. The data is then smoothed using a ten year average which is ideally suited to removing the past five years of the past decade and mix the earlier standstill years with years when there was an increase. This is an ideal formula for suppressing the past decade’s data.
When examined more objectively Best data confirms the global temperature standstill of the past decade. That the standstill should be present in land only data is remarkable. There have been standstills in land temperature before, but the significance of the past decade is that it is in the era of mankind’s postulated influence on climate through greenhouse gas forcing. Predictions made many times in the past few years suggest that warming should be the strongest and fastest in the land data.
Only a few years ago many scientists and commentators would not acknowledge the global temperature standstill of the past decade. Now that it has become unarguable there has emerged more explanations for it than can possibly be the case.
To explain the combined sea-land temperature hiatus some have suggested that the oceans are sucking up the heat, as professor Muller outlines in his radio interview. This explanation is strained in my view if the land temperature stays constant. Could we really have the very special situation whereby the oceans sequester just enough heat at just the right time to keep the land temperature flat? Aerosols, postulated by some to be coming from China, don’t provide an explanation for the land temperature hiatus either. In fact, the constant land temperature puts a strain on all of the explanations offered for why the land-sea combination hasn’t warmed in the past decade or so.
We make a big deal of the temperature going up. In my view we should make a bigger scientific deal about temperature flatlining for a decade or more in the face of rising CO2 levels. If further scrutiny of the Best dataset confirms this finding we will have new questions about the nature and balance of oceanic and land warming.
The fact that Best confirms the global temperature hiatus and shows that it is apparent in land only data is significant, and in my view its major scientific finding, so far. It is puzzling that they missed it.