A look at weather extremes and the big-picture climate connections.

2010 Russian Heatwave More Extreme Than Previously Thought

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Tourists brave the hot weather to see St. Basil Cathedral in Moscow last summer amidst the worst European heatwave on record. Credit: Alex Wolf/flickr.

It’s safe to say the sweltering heat wave that struck western Russia last summer brought the hottest temperatures anyone from the region could remember. After all, the daytime temperatures in Moscow surged past 100°F, and prior to last summer, the city’s all-time high temperature had never reached the century mark (with records going back as far as 1879).

The Russian heatwave was a record-breaking event by nearly any description. Now, months later, there is a new perspective on just how rare the summer of 2010 was across Europe.

Prior to 2010, the most severe heat wave on record for the continent was in 2003, when two stretches of exceptionally hot weather blanketed western European countries like France, Spain, and Germany. According to a new study that compares both the severity and areal extent of these two so-called “mega-heatwaves,” last summer’s event was more extreme than the one seven years earlier. Though not as high as those seen in 2003 (when parts of France were well above 100°F for days), the temperatures in Russia last summer were much higher than the region’s average temperatures. Heatwaves are actually measured according to how hot the temperatures get relative to what is seen on average for that time of year in a given region.

“2010 was more extreme (than 2003) just in terms of terms of temperature anomaly alone,” says climate scientist Erich Fischer from ETH Zurich in Switzerland, one of the study’s co-authors. Fischer says the 2010 heatwave was made even more extreme by the fact that, compared to 2003, the blistering heat covered nearly 400,000 square miles more land area (about double the area of the 2003 heatwave).

This new study, which was published today in the journal Science, compared heat waves only in terms of climatology. So, the researchers looked strictly at how unusual the high temperatures were for the region, and how much area was affected, and did not account for any impacts from either heat wave. As Climate Central has reported, both heat waves resulted in tens of thousands of deaths, damaged food crops, and serious forest fires.  

The study also uses a reconstruction of European temperatures going back to 1500, based on old log-books and other sources. These records are of course less precise than more modern ones that cover the past 140 years. Nonetheless, even when accounting for the errors that this more uncertain data introduces, Fischer says the evidence points at the events of 2010 and 2003 as being unusually extreme — particuarly because they happened within the same decade — and likely the hottest in the last 500 years. 

Moreover, Fischer and his colleagues from the University of Lisbon in Portugal, the Justus-Liebig-University of Giessen in Germany and the Spanish Meteorological Agency looked at what is in store for future European summers. Using 11 different regional climate models to project what future conditions will accompany increasing greenhouse gas emissions, the group found that these so-called “mega-heatwaves” — those of the 2003 and 2010 severity — will become more frequent.

So, if these major heat waves are happening more often, will what is thought of as extreme today still be considered extreme 10, 50 or even a hundred years from now?

“2010 was so extreme that even within the next century it will still be a very unusual event,” says Fischer. However, 2003 offers a different example. “The 2003 type of summer is already becoming more common and it will be close to a normal summer towards the end of the century.”

This new study’s prognosis that summers like that of 2003 and 2010 are bound to be a more regular occurrence is in agreement with a NOAA study of the Russian heatwave released on March 9. Unlike in the NOAA study, however, Fischer and his colleagues didn’t attempt to investigate whether human influences — by way of man-made greenhouse gases — played any role in the 2010 heat.

“(Our study) wasn’t focusing on what the cause was,” says Fischer, “But in a general sense we can’t say whether it was natural variability or if there was anthropogenic [manmade] influence, the models don't give us a robust enough analysis for this.”

Since the NOAA study was released, which indicated that the 2010 heat wave could not be attributed to long-term climate change, other scientists have questioned whether that group’s analysis was sufficient to make such a strong claim. In particular, Kevin Trenberth, head of the climate analysis section at the National Center of Atmospheric Research in Boulder, Colo., says the NOAA analysis was not extensive or robust enough to fully explain the 2010 heat wave.

In an interview with Joseph Romm at Climate Progress, Trenberth says:

The paper focuses on the Russian heat wave in July 2010. But it has an extremely narrow focus and does not examine conditions elsewhere in the hemisphere. The atmospheric circulation is global and interlinked over thousands of miles. It so happens that record breaking flooding occurred in July in China and India, to be followed by record breaking flooding in Pakistan in August. Is this a coincidence? No, it is not but these events are never mentioned.

An important but as yet unanswered question about the 2010 heatwave is what caused the “exceptionally strong blocking event” that NOAA’s Martin Hoerling and Randall Dole attribute to maintaining the extreme high temperatures over Russia. According to Trenberth, the climate models used to investigate the 2010 event thus far don’t accurately account for other factors that may have influenced European climate last summer, including the Asian Monsoon and even La Nina in the Pacific. Until those factors can be incorporated into a full analysis of the heatwave, it will not be possible to say what role greenhouse gas emissions played in the severity of last summer’s heat in Russia.

“As models get better, we will revisit these kind of events,” Trenberth says, “And I expect we will see some other interesting things as well.” 

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