2010 Russian Heat Wave

In 2010 large swaths of the earth were hit by extreme weather in the form of heat waves. The effects were particularly strong in Russia, where numerous records for the hottest day across the country were broken (or smashed in some cases). Over 50,000 deaths were reported in Russia (Khandekar et al., 2013), and according to the Guardian, temperatures were around 10C above their seasonal average and there were substantial damages to the wheat harvest, costing the Russian economy $15bn. The cause of the heat wave was a blocking anticyclone over Russia, that was maintained by "anomalous cyclonic conditions over the Mediterranean area" and a similarly anomalously strong monsoon circulation (Trenberth et al., 2012). This blocking high lead to a temperature inversion which trapped exhaust fumes close to the ground, leading to some pretty horrendous conditions in Moscow:

Moscow on the 17th of June and 10th of August

From this it's clear that the human costs of extreme weather can be devastating, even when the extreme weather is not in the form of a one off extreme event such as a hurricane or a flood. The question of attribution of these events is therefore hugely relevant to the debate on climate change, because if it were to be shown that these events were caused by a warming climate, then this would directly link anthropogenic influences to huge economic and human costs.

How can a single event be attributed to a warming climate?

It is notoriously difficult to attribute a single given event to climate change. Indeed, it may well be a futile task, here is part of a paper examining the role climate change had on the 2003 heat wave in Europe (Stott et al, 2005): 

It is an ill-posed question whether the 2003 heatwave was caused, in a simple deterministic sense, by a modification of the external influences on climate—for example, increasing concentrations of greenhouse gases in the atmosphere—because almost any such weather event might have occurred by chance in an unmodified climate.

The paper goes on to examine the link between increased global temperatures and the risk of a given event happening. That is, assuming that there's no direct connection between the event and global warming, rather there's a possibility of increased statistical likelihood that the event was caused by climate change. They find that this was the case for the 2003 heat wave in Europe, through a method of comparing the temperature in 2003 against a number of simulations using the HadCM3 model for the same area and seeing if the value was outside of statistically significant levels.

Was there a greater risk of the 2010 Russian heat wave because of a changed climate?

In this paper: Was there a basis for anticipating the 2010 Russian heat wave? (Dole et al., 2011), the authors find that "the intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability". They use a range of techniques to draw this conclusion, using CMIP3 models and also comparing the heat wave temperatures against historical temperatures for the region. Indeed, this provides the main evidence for their conclusion about the attribution of the event to climate change, making it differ slightly in its methodology to Stott et al. (The model simulations were more involved in trying to hindcast the event than as part of the study of attribution.) This means that their approach for attributing 'blame' is mainly empirical in nature, as opposed to the more model orientated methods used in Stott et al.

Conclusion

It's impossible to say that any one event was 'caused' by climate change. However, it is perfectly reasonable to apportion an amount of blame to climate change, as was done by Stott et al. for the European heat wave. Whereas for the Russian heat wave it is "very unlikely that warming attributable to increasing greenhouse gas concentrations contributed substantially to the magnitude of this heat wave". So is it fair to say that the 2010 heat wave had no link to climate change? On the face of this post's evidence, yes, but things aren't always clear cut in science, and in a future post I'm going to have a look at a paper that finds itself in explicit contradiction to the Dole et al. paper, and see if there's any way of resolving this apparent contradiction.

EDIT:

See this post then for the next in the series, and this post for the final instalment.