Environment Counts | Attribution of Extreme Weather Events in the Context of Climate Change :

A recent report by the US National Academy of Sciences provides an overview of the current state of the science of attribution of extreme weather events and sets out a series of recommendations for future avenues of research in this field. It addresses the need for improved understanding of this issue at a time when there is increasing inquiry by the public, policymakers, and practitioners about the relations between specific weather events and climate change (e.g., the question “Is it caused or affected by climate change”).

The report concentrates on the need for effective, rigorous, and scientifically defensible analysis of the attribution of extreme weather events to changes in the climate system. The report does not attempt to summarise the World’s recent extreme weather events. Instead it draws on the experience of panels of scientists to provide guidelines for future research, methodologies and recommendations for more focused and detailed data in this field. The report also provides some interim conclusions, including the following.

• Confidence in attribution analyses of specific extreme events is highest for extreme heat and cold events, followed by hydrological drought and heavy precipitation. There is little or no confidence in the attribution of severe convective storms and extratropical cyclones.

• Attribution of events to anthropogenic climate change may be complicated by low frequency natural variability, which influences the frequencies of extreme events on decadal to multidecadal timescales.

• Confidence in attribution findings of anthropogenic
  

  influence is greatest for those extreme events that are related to an aspect of temperature, such as the observed long-term warming of the regional or global climate, where there is little doubt that human activities have caused an observed change.

• A definitive answer to the commonly asked question of whether climate change “caused” a particular event to occur cannot usually be provided in a deterministic sense, because natural variability almost always plays a role.

• Attribution studies of individual events should not be used to draw general conclusions about the impact of climate change on extreme events as a whole.

The report notes that in 2012 the American Meteorological Society started to publish a special annual issue of their Bulletin, compiling articles on extreme weather events of the past year. From 2012 to 2015, the number of research groups submitting studies to this issue grew by more than a factor of five. A prime goal of this report is to provide a snapshot of the current state of the science of attribution of extreme weather events and to provide recommendations for what might be useful future avenues of both research and applications within this field.
Attribution of Extreme Weather Events in the Context of Climate Change. 2016 National Academy of Sciences