Extreme weather leads to extremely different headlines
The majority of Americans believe that climate change is making extreme weather events worse, according to a new poll released today by Yale University and George Mason University. But do the scientists working in the field of climate attribution agree?
It’s hard to tell from reading media reports about extreme weather, as there seems to be some confusion in the media about its link to man-made climate change. For example, headlines about the recent release of the IPCC’s Special Report into Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) ranged from Climate change ‘behind extreme weather conditions’, to UN climate panel ties some weather extremes to global warming, and New U.N. report blows cold on human causes for weather extremes.
Most of the articles about SREX don’t really capture the nuances of the report’s findings, and it would be easy to blame the media for this. But is it all down to the media, or does this wide ranging media coverage reflect the diverse range of opinions held by scientists working in the field?
New York Times blogger Andrew Revkin has canvassed some extreme weather experts for their views on the topic. This was instigated by a Perspectives article from Stefan Rahmstorf and Dim Coumou, of the Potsdam Institute for Climate Impact Research, published a few weeks ago in the journal Nature Climate Change. Rahmstorf and Coumou review the evidence on heat extremes, rainfall extremes and storms from over the last decade, and argue that there is sufficiently strong evidence to link certain types of extreme weather events – or an increase in their numbers – to human influence on the climate.
The piece was fairly widely reported by news outlets, although few noted that it was not a research article, but a Perspective article, which do not typically present new data, but are, according to the Nature Climate Change website,”intended to provide a forum for authors to discuss models and ideas from a personal viewpoint”.
Revkin asked other scientists working in the field for their responses to the Rahmstorf and Coumou article and found a whole array of opinions on the article, the links between extreme weather events and man-made climate change, and how it is being communicated.
Dr Martin Hoerling, who leads the climate-extremes attribution team at the US National Oceanic and Atmospheric Administration calls the article an op-ed, using “[e]xaggerated language, and many unsubstantiated assertions”, written in a “policy-direct tone”. He says:
“The matter of attribution, as raised in the second to last paragraph, is a much broader science than merely determining the change in probability due to greenhouse-gas forcingâ?¦.which is an inherently difficult and uncertain undertaking. The piece ignores the broader context in which all manner of contributing factors is assessed to understand the magnitude of events, their temporal and regional specificity […] After all, the irony of extreme events is that the larger the magnitude the smaller the fractional contribution by human climate change.”
John Wallace, climate scientist at the University of Washington agrees:
“My reactions to the article are very much along the same lines as Marty Hoerling’s. By exaggerating the influence of climate change on today’s weather and climate-related extreme events, a part of our community is painting itself into a rhetorical corner.”
But Kerry Emanuel, Professor of Atmospheric Science at the Massachusetts Institute of Technology, takes a different view:
“I read the piece differently from the way […] Martin [Hoerling] read it […] I did not read it as a scientific paper or letter.”
Emanuel finds the piece useful as it draws attention to the point that extreme weather affects society more than average weather, although he feels it focuses too much on anecdotes, detracting from the statistical analysis. He says:
“[T]here is so much literature on the the mean temperature response that I believe there is room to draw attention to the problem of extremes.”
Rahmstorf responds to the comments at Revkin’s blog, saying:
“There is a broad spectrum of views on extreme events in the community – you’ve sampled some of those. It is precisely this range of opinions which made us think it worthwhile to take a good dispassionate look at the evidence and stimulate some discussion. We noticed this range also in the reviews of our Perspective. One reviewer asked us to make stronger statements on the link between climate change and extremes, another just asked the opposite and the third one found we got it about right.”
So there’s clearly a range of opinions among those in the field, as is typical for an emerging branch of science. It is, therefore, understandably hard for the media – looking for a straightforward story – to accurately convey what’s going on in the field of extreme weather attribution.
But one thing on which scientists largely seem to agree is that the SREX report represents the ‘best current synthesis’ of the state of understanding of climate extremes in a warming world. It is strange then that there was such a range in take-home messages attributed to SREX in media reports. Some of the media inaccuracy around reporting of extreme events may well have arisen from active misinterpretation. For example, the UK climate skeptic lobby group the Global Warming Policy Foundation has been accused of “cherry picking” from SREX “to make it sound benign”.
So what should be the take-home message for extreme weather attribution? Perhaps it’s best summed up in this slightly uninspiring line from the SREX Summary for Policymakers:
“There is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases […] Attribution of single extreme events to anthropogenic climate change is challenging.”
Enough said.