The Current Wisdom only comments on science appearing in the refereed, peer‐reviewed literature, or that has been peer‐screened prior to presentation at a scientific congress.
The recent publication of two articles in Nature magazine proclaiming a link to rainfall extremes (and flooding) to global warming, added to the heat in Russia and the floods in Pakistan in the summer of 2010, and the back‐to‐back cold and snowy winters in the eastern U.S. and western Europe, have gotten a lot of public attention. This includes a recent hearing in the House of Representatives, despite its Republican majority. Tying weather extremes to global warming, or using them as “proof” that warming doesn’t exist (see: snowstorms), is a popular rhetorical flourish by politicos of all stripes.
The hearing struck many as quite odd, inasmuch as it is much clearer than apocalyptic global warming that the House is going to pass meaningless legislation commanding the EPA to cease and desist from regulating greenhouse gas emissions. “Meaningless” means that it surely will not become law. Even on the long‐shot probability that it passes the Senate, the President will surely veto, and there are nowhere near enough votes to override such an action.
Perhaps “wolf!” has been cried yet again. A string of soon‐to‐be‐published papers in the scientific literature finds that despite all hue and cry about global warming and recent extreme weather events, natural climate variability is to blame.
Where to start? How about last summer’s Russian heat wave?
The Russian heat wave (and to some degree the floods in Pakistan) have been linked to the same large‐scale, stationary weather system, called an atmospheric “blocking” pattern. When the atmosphere is “blocked” it means that it stays in the same configuration for period of several weeks (or more) and keeps delivering the same weather to the same area for what can seem like an eternity to people in the way. Capitalizing on the misery in Russia and Pakistan, atmospheric blocking was added to the list of things that were supposed to be “consistent with” anthropogenically stimulated global warming which already, of course included heat waves and floods. And thus the Great Russian Heat Wave of 2010 became part of global warming lore.
But then a funny thing happened — scientists with a working knowledge of atmospheric dynamics started to review the situation and found scant evidence for global warming.
The first chink in the armor came back in the fall of 2010, when scientists from the Physical Sciences Division (PSD) of the Earth System Research Laboratory (ESRL) of the National Oceanic and Atmospheric Administration (NOAA) presented the results of their preliminary investigation on the web , and concluded that “[d]espite this strong evidence for a warming planet, greenhouse gas forcing fails to explain the 2010 heat wave over western Russia. The natural process of atmospheric blocking, and the climate impacts induced by such blocking, are the principal cause for this heat wave.”
The PSD folks have now followed this up with a new peer‐reviewed article in the journal Geophysical Research Letters that rejects the global warming explanation. The paper is titled “Was There a Basis for Anticipating the 2010 Russian Heat Wave?” Turns out that there wasn’t.
To prove this, the research team, led by PSD’s Randall Dole, first reviewed the observed temperature history of the region affected by the heat wave (western Russia, Belarus, the Ukraine, and the Baltic nations). To start, they looked at the recent antecedent conditions: “Despite record warm globally‐averaged surface temperatures over the first six months of 2010, Moscow experienced an unusually cold winter and a relatively mild but variable spring, providing no hint of the record heat yet to come.” Nothing there.
Then they looked at the long‐term temperature record: “The July surface temperatures for the region impacted by the 2010 Russian heat wave shows no significant warming trend over the prior 130‐year period from 1880 to 2009… . A linear trend calculation yields a total temperature change over the 130 years of -0.1Â°C (with a range of 0 to -0.4Â°C over the four data sets [they examined]).” There’s not a hint of a build‐up to a big heat wave.
And as to the behavior of temperature extremes: “There is also no clear indication of a trend toward increasing warm extremes. The prior 10 warmest Julys are distributed across the entire period and exhibit only modest clustering earlier in this decade, in the 1980s and in the 1930s… . This behavior differs substantially from globally averaged annual temperatures, for which eleven of the last twelve years ending in 2006 rank among the twelve warmest years in the instrumental record since 1850… .”
With regard any indication that “global” warming was pushing temperatures higher in Russia and thus helped to fuel the extreme heat last summer, Dole et al. say this: “With no significant long‐term trend in western Russia July surface temperatures detected over the period 1880–2009, mean regional temperature changes are thus very unlikely to have contributed substantially to the magnitude of the 2010 Russian heat wave.”
Next the PSD folks looked to see if the existing larger‐scale antecedent conditions, fed into climate models would produce the atmospheric circulation patterns (i.e. blocking) that gave rise to the heat wave. The tested “predictors” included patterns of sea surface temperature and arctic ice coverage, which most people feel have been subject to some human influence. No relationship: “These findings suggest that the blocking and heat wave were not primarily a forced response to specific boundary conditions during 2010.”
In fact, the climate models exhibited no predilection for projecting increases in the frequency of atmospheric blocking patterns over the region as greenhouse gas concentrations increased. Just the opposite: “Results using very high‐resolution climate models suggest that the number of Euro‐Atlantic blocking events will decrease by the latter half of the 21st century.”
At this point, Dole and colleagues had about exhausted all lines of inquiry and summed things up: