So, I was going to have a break and stop writing, but clearly I don’t know when to give up. I’ve also just noticed that this will be my 150th post since I started in April. That’s either impressive, or slightly sad, or maybe some combination of the two. Anyway, Watts Up With That (WUWT) has new post called NOAA: Another ‘AGW caused heat wave’ is actually just natural variation. It discusses an early online release of a paper to be published in the Bulletin of the American Meteorological Society called, The Making of an Extreme Event: Putting the pieces together.
Now, I’m not all that comfortable discussing climate change specifically as it’s even more out of my comfort zone than global warming (to which I can at least apply basic physics), but I downloaded and started reading the paper. Not in great detail, but just scanning through the abstract and introduction. I noticed the following in the abstract
We conclude that the extreme warmth over the central and eastern U.S. in March 2012 resulted primarily from natural climate and weather variability, a substantial fraction of which was predictable.
I then notice this in the Introduction
Temperatures in 1910 were nearly as warm as in 2012 over the contiguous U.S., with a mean departure in 1910 relative to the 20th century average of +4.5oC (compared to +4.8°C in 2012). The global temperature patterns for both months, though separated by over a century, are also strikingly similar.
I’m now starting to think that this paper is actually claiming that the extreme weather seen in March 2012 was essentially the same as that seen in 1910 and, hence, that it can all be attributed to some natural variation. Maybe WUWT was actually correct. Kudos.
Then I get to Figure 1, which I include below. But hold on a moment, this figure appears to be comparing the March 1910 temperature anomalies with temperature anomalies for March 2012 that have been detrended (i.e., the long-term warming trend has been removed from the bottom-right panel in Figure 1). The paper actually goes on to say The resulting detrended March 2012 temperature anomaly pattern is almost the same as March 1910 over the central U.S. as well as many other parts of the globe. Hmmm, this suggests that it’s not all just due to natural variation.
I then get to the final figure, which I also include below. This is an illustration showing how the temperature distribution in March 2012 (red curve) can be regarded as a consequence of an underlying climatological distribution (black curve), plus a long-term trend (to give the blue curve), plus seasonal variations (to give the green curve), plus natural variations.
So, Anthony Watts, this paper is not saying what you think it’s saying. It’s not saying that the temperature seen in March 2012 was precisely the same as in March 1910. It’s saying that the variations in temperature (around the mean) were the same in March 2012 as they were in March 1910. The conclusion one could draw is that what drove the extreme weather in March 2012 could be the same as what drove it in March 1910. However, in March 2012 there was an additional effect, which was that the long-term warming had increased the average temperature by about 1oC.
Now, I should acknowledge that I was reading it all a little quickly when I started, so missed the following comment in the abstract
The results indicate that the superposition of a strong natural variation similar to March 1910 on long-term warming of the magnitude observed would be sufficient to account for the record warm March 2012 U.S. temperatures.
All a little obvious really, although I do think they did make it quite hard, initially, to work out that they were comparing the detrended variations in March 2012 with the variations in March 1910. Given how papers like this can so easily be mis-understood (or mis-represented?) by those who are skeptical of global warming/climate change, it would seem important to make this distinction extremely clear.