Killer Russian heatwave product of climate change

Killer Russian heatwave product of climate change

26 October 2011

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Russia — Last year’s Russian heatwave and drought resulted in vast wildfires and a mortality rate that was 56,000 people higher than the same period in 2009. Now, researchers have published a paper in the Proceedings of the National Academy of Sciences (PNAS) that finds the heatwave would very likely have never happened if not for climate change. The study flies in the face of previous research by the National Oceanic and Atmospheric Administration (NOAA) that concluded the heatwave was simply due to natural variation and not a warming world.

Image of Russia and nearby areas from August 4th, 2010 by NASA’s Moderate Resolution Imaging Spectroradiometer.
Especially intense fires are outlined in red. Smoke from peat and forest fires lead to dangerous levels of pollution
throughout Moscow and surrounding areas. Photo by: NASA.

Looking at local warming in the region from 1880 to 2010, Stefan Rahmstorf and Dim Coumou with the Potsdam Institute for Climate Impact Research found an 80 percent likelihood that the heatwave was due to climate change.

“For July temperature in Moscow, we estimate that the local warming trend has increased the number of records expected in the past decade fivefold, which implies an approximate 80 percent probability that the 2010 July heat record would not have occurred without climate warming,” Rahmstorf and Coumou write.

However, what about the fact that a previous study from NOAA found no evidence of a climate changes signature in the Russian heatwave?

According to the new study, NOAA researchers over-corrected for the urban heat island effect. Urban heat island effect is when a city shows slightly warmer temperatures than surrounding countryside, and is regularly taken into by climatologists. However, in this case the new study argues treating the urban heat island effect as the same in winter and summer doomed the NOAA study to underestimate recent warm trends in Moscow.

“[The NOAA study] leads to a massive over-adjustment for urban heat island in summer, because the urban heat island in Moscow is mostly a winter phenomenon. This unrealistic adjustment turns a strong July warming into a slight cooling,” Rahmstorf and Coumou write in a blog entry on Real Climate.

Recalculating the over-adjustment, the authors found evidence of significant warming in Moscow in July.

“[Satellite data shows] for a large region around Moscow a linear warming of 1.4 degrees Celsius over the period 1979-2009. That is (even without the high 2010 value) a warming three times larger than the global mean!”

The subsequent heatwave, drought, and fires destroyed 20 percent of Russia’s massive wheat harvest, pushing the government to ban wheat exports for the year. This had global implications on food security and prices.

During the disaster, Russian President Dmitry Medvedev told a Russian Security Council meeting, “Unfortunately, what is happening now in our central regions is evidence of this global climate change, because we have never in our history faced such weather conditions in the past. This means that we need to change the way we work, change the methods that we used in the past.”

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