Attribution of Extreme Weather Events in the Context of Climate Change

• Examines the current state of science of extreme weather attribution and identifies ways to move the science forward to improve attribution capabilities
• States that some impacts of global warming on extreme events are well understood—including that warming increases the likelihood of extremely hot days and nights, favors increased atmospheric moisture that may result in more frequent heavy rainfall and snowfall, and leads to evaporation that can exacerbate droughts
• Looks at the relatively young science of extreme event attribution, which seeks to tease out the influence of human-cause climate change from other factors, such as natural sources of variability like El Niño, as contributors to individual extreme events
• Concludes it is now “often possible” to describe how human-induced climate change altered the likelihood and/or intensity of a specific extreme weather event

Quotes

"Like the surgeon general’s 1964 report connecting smoking to lung cancer, the report from the National Academies connects global warming to the increased risk and severity of certain classes of extreme weather, including some heat waves, floods and drought."

Heidi Cullen, Chief Scientist for Climate Central and head of the World Weather Attribution program

"Climate science works best with patterns. Determining climate change’s role in a single event is usually more difficult than doing so in global statistics. It can be hard to be sure that exposure to small amounts of a chemical caused cancer in a single patient, even when studies of large populations prove that it is a carcinogen; similarly, we often can’t make strong attribution statements about an individual weather event, even when we have a lot of evidence that those kinds of events overall are influenced by climate change, or will be in the future. So media coverage of attribution studies sometimes ends up focusing more on what we don’t know than what we do. That can leave the impression that we know less than we really do, which is unhelpful in a political climate which already doesn’t take the real one seriously enough."

Adam Sobel, Professor of Applied Physics and Applied Mathematics and of Earth and Environmental Sciences at Columbia University

"The fog of uncertainty that obscured the human role in individual events is finally lifting."

Michael Oppenheimer, Princeton University professor

"The National Academies report should go a long way toward the 'mainstreaming' of attribution research. It will also help journalists, educators, and others who need to put this often-esoteric science into terms that people can easily grasp. The links between greenhouse gases and extreme weather are far too important and intricate to be dismissed or broad-brushed."

Bob Henson, Weather Underground Meteorologist