2010 Russian Heat Wave - An Alternative Approach

Following this month's earlier post on the same topic, I'd like to have another look at the Russian 2010 heat wave. The previous post focussed mainly on a paper which found that there was no reason to suspect global warming was to blame for the heat wave (Dole et al., 2011). It's worth repeating one of this paper's main findings: "We conclude that the intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability".

Scientific consensus?

However, there's a difference of opinion expressed by other climate scientists, who find that there was an increased likelihood of the Russian heat wave of 2010 because of global warming (Rahmstorf and Coumou, 2011). The approach they take is appealing because of its simplicity: they use straightforward arguments based on the statistics of such events and a combination of Monte Carlo simulations and analytical solutions. The conclusions they draw are not hard to understand either: if you assume there is an underlying upward trend in the time series with some random noise added to this then you would expect there to be a higher chance of observing an extreme event towards the end of the time series than if the time series were stationary (i.e. no underlying trend). A simple visual representation of this can be seen in the graph below, which shows the average global (D) and Moscow (E) temperature record over the last 100 years.

Normalised (by the s.d.) temperature records for the Earth (D) and Moscow (E)

Using this line of reasoning they find that there is an 80% chance that the 2010 Russian heat wave was caused by the underlying warming trend, and they point out that "Our results thus explicitly contradict those of Dole et al.".

They also claim that "Fig. 4 clearly shows that the warming trend after 1980 has multiplied the likelihood of a new heat record in Moscow and would have provided a strong reason to expect it before it occurred.". This is again in contrast to the Dole et al. paper, which says that it was unpredictable. I think the resolution of these two points of view is fairly easy though: the ability to predict an event is far tougher than merely expecting that an event might happen.

In a final post on this topic in the new year I'm going to see whether these two different takes on the same event can be reconciled.

EDIT:

The final post is now up, take a look here for the final instalment.