Tuesday, May 3, 2016

Can Extreme Weather Events be Attributed to Climate Change?

Attribution of Extreme Weather Events in the Context of Climate Change (163 page pdf, Committee on Extreme Weather Events and Climate Change Attribution; Board on Atmospheric Sciences and Climate; Division on Earth and Life Studies; National Academies of Sciences, Engineering, and Medicine, Mar. 17, 2016)

 Also discussed here: Global Warming Is Happening FAST, but Is It Causing Extreme Weather Events?(Astrid Caldas, Union of Concerned Scientists, Mar. 11, 2016)

Today we review a major effort to answer the question: how does climate change affect extreme weather events? This was investigated using two well known approaches: the long term statistics of meteorological parameters and through simulations using physical climate models. Although much more research is needed, several conclusions were made including a main one that some types of extreme weather events (such as extreme cold and heat events) are more easily understood and attributable to climate change than others (such as wildfires and severe convective storms and tornadoes) . This, in turn, is linked to the ability of models to simulate and physically represent large scale temperature events covering continents more effectively than those on an urban or smaller scale that involve fine scale precipitation patterns. Another major finding was that it is impossible to absolutely link climate change alone to a single extreme event because of the role that natural variability almost always plays. Attribution-capability-by-type-event  

Key Quotes:

“each extreme event is a consequence of multiple factors under a set of conditions—much like a cookie is the product of various ingredients and conditions. You tweak one ingredient or condition and the result will be slightly different, while still remaining a cookie—or in our case, an extreme event.”

 “Events related to an aspect of temperature (such as warming) are easier to attribute than events that have a variety of other influences….there is high confidence on the capability of attribution and high understanding of the effects of climate change on heat waves and cold waves, but not hurricanes or droughts, which involve a lot more complex interactions both physical and human-induced.”

“If one is able find out whether an event had climate change as a major component, then one can estimate if similar events will be more likely in the future, and plan for risk reduction and adaptation strategies”

“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.”

“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.”

“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.”

No comments:

Post a Comment