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Climate Change and Particular Weather Events: Revisiting Recent Research

Russialsta_tmo_2010208_lrgDavid Sandalow, Acting Undersecretary of Energy and Assistant Secretary for Policy and International Affairs at the U.S. Department of Energy, recently spoke at the Columbia University Energy Symposium about Hurricane Sandy, its impacts on our energy infrastructure, and what we can expect in a climate-changing world. Addressing climate change, he states:

…we ignore the climate threat at our peril. While we can’t attribute any particular weather event to climate change, we do know the temperature around the globe is increasing faster than was predicted even 10 years ago. We know that the Arctic ice cap is melting faster than was predicted even five years ago. We know that there have been more severe weather events here in North America, but also around the globe.

By one calculation, every incremental inch of storm surge in New York City displaced an additional 6,000 people. Sea level has already risen 7 inches in the last 100 years and is projected to rise more than 30 inches in the next 100.

President Obama is a firm believer that climate change is real, that it is impacted by human behavior and carbon emissions. And as a consequence, we have an obligation to do something about it.

To meet this threat, we must plan wisely, improve our infrastructure and cut emissions of heat-trapping gases. The transition to a clean energy economy can help mitigate risks from extreme weather events and is a powerful driver of economic progress.

A dire picture, to be sure. But while Assistant Secretary Sandalow rightly states that it is difficult to draw a direct line of causality from climate change to specific weather events, recent peer-reviewed research has yielded probabilistic results which make it possible to draw some very explicit connections between climate change and very specific weather events.

For example, earlier this year we reported on two separate studies that demonstrated statistically-significant connections between the Russian heat wave of 2010 and climate change. Here is the full piece:

Last October, we highlighted a study by Rahmstorf and Coumou which, through utilizing a Monte Carlo simulation, found that the Russian heat wave of 2010 had an 80% likelihood of being attributed to a long-term climatic warming trend. The finding was significant because it seemed to contradict an earlier study by Dole et al, highlighted by Andrew Revkin of the New York Times, that did not find evidence of a climate change link, and thus asserted that the link did not exist. This was, in the words of Rahmstorf and Coumou, a case of confusing “an absence of evidence” with “evidence of absence.”

Now, a new multi-model study by Allen et al, which got some coverage at the Guardian last month, seems to have reconciled the two camps, showing that “there is no substantive contradiction between these two papers, in that the same event can be both mostly internally-generated in terms of magnitude and mostly externally-driven in terms of occurrence-probability.” In other words, while it doesn’t necessarily take climate change to produce a heat wave of that scale, it is highly unlikely that the heat wave would have occurred without it. The two studies were simply asking different questions. Not surprisingly, their answers were different, and it shouldn’t surprise us that those answers can peacefully (and intellectually) coexist!

However, beyond this virtuous and rare act of evidence-based academic diplomacy, the study by Allen and his colleagues ultimately confirms the essential finding of Rahmstorf and Coumou, stating that the “Russian heat wave 2010 [is] likely attributable to anthropogenic climate change.”

Given that findings from multi-climate model simulations like this one are inherently sturdier than those utilizing single models, this is strong evidence indeed.

Furthermore, a NOAA study published last October in the Journal of Climate found strong and observable evidence that the recent prolonged period of drought in the Mediterranean littoral and the Middle East is linked to climate change. The study also found worrying agreement between observed climate impacts, and future projections from climate models.

In short, while the scientific and policy-making communities must be very careful not to make premature or spurious claims about the connections between climate change and specific weather events, there exist powerful scientific tools to aid us in those inquiries, and some of them have already yielded compelling results. This will be an area to watch, and watch closely.


  1. Simon Dalby says:

    Folks: What is or isn’t caused by climate change is an awkward formulation for discussing these matters. Indeed Kevin Trenberth suggests, in “Framing the way to relate climate extremes to climate change” (Climatic Change 115. 2012. 283-290) that this isn’t a helpful question because human actions are part of the climate system, not a separate add on to a prior system.

  2. Caitlin Werrell and Francesco Femia says:

    Thanks Simon. You make an important point. The aim of the post was not so much about framing a discussion, but about highlighting recent scientific research. The two studies we cited demonstrate that climate change did increase the likelihood of the Russian heat wave, and that’s all we wanted to highlight. In general, we agree with you. Usually, talking about whether or not climate change caused specific weather events does not make for fruitful discussion.

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