Christopher Monckton has a new post at Watts Up With That (WUWT) called is it time to prosecute the IPCC for fraud? In case you have a short attention span, the simple answer to Christopher’s question is “no”.
So, why does Christopher think we should consider prosecuting the IPCC for fraud. Well, it’s because he objects to the figure below that was included in the IPCC’s 4th Assessment Report.
He seems to object for two reasons. One seems to be that if the temperature anomaly was simply following some kind of sine wave like oscillation, you could get this result (by fitting to the rising portion of the sine wave) even if the mean trend was flat. Sure, but there is no evidence that it is following some kind of long timescale sinusoidal variation. Just because you could get this if the variation was the rising part of a long timescale sine wave, doesn’t mean that that is the reason. There is no known mechanism that could produce such a variation in the temperature anomaly data. The other issue is that the trend has been flat for the last decade. Sure, the mean has been close to zero, but the errors are large and the trend for the last decade or so is strongly influence by the large ENSO event that occurred in the late 90s.
Personally, I do have one issue with this figure which is that by considering ever shorter time intervals, the error in the trends get larger. They do include the errors, so this isn’t hidden. The argument that could be made is that with large errors you can’t claim with certainty that the trend has been getting larger (or, at least, the trends for the last 25 and 50 years are statistically consistent with each other). In an earlier post (is global warming accelerating), I suggested that what they should have done is fixed the start year, but varied the end year. This way not only do you show that the trend is getting larger, the errors get smaller and so the acceleration is statistically significant.
So, what else does Christopher say. Well, he says
The conclusion the IPCC draws by superimposing multiple trend-lines on the HadCRUt curve of global mean surface temperature anomalies since 1850 is that because the trend-lines starting more recently are steepest the world is warming ever faster and we are to blame. The caption to the graph makes this clear:
I disagree. That isn’t actually what the caption says. Firstly, it refers to the trend lines as simple fits, so doesn’t make any claim that these are some kind of detailed analysis. When it discusses our influence, it actually says
Results from climate models driven by estimated radiative forcings for the 20th century (Chapter 9) suggest that there was little change prior to about 1915, and that a substantial fraction of the early 20th-century change was contributed by naturally occurring influences including solar radiation changes, volcanism and natural variability. From about 1940 to 1970 the increasing industrialisation following World War II increased pollution in the Northern Hemisphere, contributing to cooling, and increases in carbon dioxide and other greenhouse gases dominate the observed warming after the mid-1970s.
So, the report does not use the trends getting steeping as the evidence that we are to blame. What the report does is show that the change in surface temperature is accelerating (and I would argue that this is indeed correct) and then reports that detailed modelling indicates that increases in carbon dioxide and other greenhouse gases dominate the observed warming after the mid-1970s. So, the data is consistent with this, but it isn’t the data alone that is leading scientists to conclude that we have been significantly influence global warming since the mid-1970s. Furthermore – as I’ve mentioned in many posts – changes in the global surface temperature is not the only indicator of global warming. Global warming is, fundamentally, about increasing energy and there are many other indicators that global warming is indeed happening.
So, to suggest that the IPCC should be prosecuted because they’ve included a figure that is not actually incorrect but (according to Christopher) could be misleading if the temperature anomaly is actually following some kind of long-term variation that cannot be explained by any known physics, is absurd. Personally, I think that making such a suggestion is a very risky thing to do. If we were to start prosecuting people and/or organisations who’ve presented misleading information about global warming/climate change (and I’m not suggesting here that the IPCC has done this) it could really come back to haunt Christopher and others at WUWT.