Initiatives / Climate
World Weather Attribution (WWA)

World Weather Attribution (WWA) is an international effort designed to sharpen and accelerate the scientific community’s ability to analyze and communicate the possible influence of climate change on extreme-weather events such as storms, floods, heat waves and droughts.

Burgess COMMENTARY

Peter Burgess

https://wwa.climatecentral.org/

World Weather Attribution

WEATHER@HOME

Hurricane Harvey

Texans continue the slow recovery from Hurricane Harvey, one of the worst weather disasters in the history of the United States. The Category 4 hurricane slammed into the Gulf Coast about 30 miles northeast of Corpus Christi on August 25. The storm and the catastrophic flooding that resulted from record rains—topping four feet of water in parts of the state—led to the deaths of at least 82 people, according to state officials. At the height of the flooding, the storm displaced more than a million residents and damaged 200,000 homes. Texas Governor Greg Abbott estimates the price tag for the disaster to run as high as $180 billion.

World Weather Attribution (WWA) received many questions about the role climate change may have played in the historic rainfall from Harvey. Researchers with WWA and its partners are conducting an attribution analysis of the deluge. The results are expected later this fall. Please continue to check this site for further updates.

WWA scientists also are assessing the possible contribution of climate change to the record heat in Europe this summer. The study will be released September 27 and the results will be available here.

Photo: Texas National Guard/flickr

Our Story

World Weather Attribution (WWA) is an international effort designed to sharpen and accelerate the scientific community’s ability to analyze and communicate the possible influence of climate change on extreme-weather events such as storms, floods, heat waves and droughts.

Recognizing society’s interest in reducing the human, economic, and environmental costs of weather-related disasters, WWA delivers timely and reliable information on how patterns of extreme weather may be affected by climate change.

The program — a partnership of Climate Central, the University of Oxford Environmental Change Institute (Oxford ECI), the Royal Netherlands Meteorological Institute (KNMI), the University of Melbourne, and the Red Cross Red Crescent Climate Centre (the Climate Centre) — was initiated in late 2014 after discussions within the scientific community concluded that the emerging science of extreme-event attribution could be operationalized.

Climate Central coordinates the program and provides its secretariat.

Identifying a human fingerprint on individual extreme-weather events —“probabilistic extreme-event attribution” — has been an important goal of the scientific community for more than a decade.

In 2004, Dr. Peter Stott of the UK Met Office and his colleagues published a paper in Nature showing that climate change had at least doubled the risk of the record-breaking 2003 European summer heat wave that is believed to have killed tens of thousands of people.

Since then, advances in the field have prompted numerous studies, leading the Bulletin of the American Meteorological Society (BAMS) to dedicate an annual special issue to extreme-event attribution for the past four years.

WWA applies a unique scientific approach that combines observational data, analysis of a range of models, peer-reviewed research, and on-the-ground reports.

This innovative combination, built on existing, peer-reviewed, methods, will enable us to conduct more rapid analyses and provide faster answers to pressing questions about high-impact events – how strong the likelihood is, for example, of similar weather-related disasters in the future.

Right now, studies of the attribution of extreme events (such as those in BAMS) require months to complete and are published long after the event.

The program will consider all types of extreme-weather events. Events that will be assessed include extreme heat and cold, heavy rainfall and floods, droughts, and also heavy snowfal and storm surges. In cases where the probability of the event appears to have been changed, we will also attempt to quantify the size of that change in order to assess the scale of the contribution from global warming. The types of events for which a quantitative analysis can be performed will expand as new attribution techniques become available and the science matures.

“The goal of this ambitious effort is to use peer-reviewed science to provide decision-makers, the public and the media with early, science-based answers to the questions of whether and to what extent global warming caused by greenhouse gas emissions played a role in an event’s probability,” said Dr. Heidi Cullen, Climate Central’s Chief Scientist. “Our team believes that a careful science-based assessment is extremely valuable, even in cases where we can’t provide hard numbers, “ said Dr. Maarten van Aalst, Director of the Red Cross Red Crescent Climate Centre. “It is important to recognize that “we don’t know” or “there is no significant trend” are also valid findings.”

This work will also help answer questions about trends in risk and vulnerability, and the role of human activity in extreme weather.

There are four possible findings of our attribution analysis of an event:
(1) Global warming increased its likelihood.
(2) Global warming reduced its likelihood.
(3) Global warming had no detectable role.
(4) Our analysis methods were unable to give information.

By providing a clear scientific statement (including about what may be uncertain), our objective is to inject more rigorous analysis and science-based information into coverage of — and public discourse on — extreme weather and its relationship with climate change.

Photo: UNICEF Philippines/2015/Jeoffrey Maitem



Analyses

WWA applies a unique scientific approach that combines observational data, analysis of a range of models, peer-reviewed research, and on-the-ground reports.

WWA uses the following criteria to decide which extreme weather events are candidates for a rapid, near real-time analysis by the partner organizations.

The event has major impacts on people

Enough usable data is available to understand what happened in terms of the meteorology in order to define the event, and there’s enough historical observations to put the event in context.

There is output of a model in principle capable of describing the event.

Researchers on the team are available and have the time for an analysis.

Complete list of studies:

Extreme Heat — Europe (2017) https://wwa.climatecentral.org/analyses/europe-heat-june-2017/

U.S. Heat (Feb. 2017) Australia Heat (Feb. 2017) S.E. Europe Cold (Jan. 2017) Somalia Drought (2016-2017) North Pole (Nov.-Dec. 2016) U.S. Deep Freeze (Dec. 2016) Kenya Drought (2016) Louisiana Downpours (August 2016) European Rainstorms (May 2016) India Heat Wave (2016) Great Barrier Reef Bleaching (March 2016) U.K.’s Storm Desmond (Dec. 2015) Chennai Floods (Dec. 2015) Record Hot Year (2015) European Heat Wave (July 2015)

Ethiopia Drought (2015) https://wwa.climatecentral.org/analyses/ethiopia-drought-2015/

Western Drought (ongoing) Southeast Brazil Drought (2014-2015) Record European Heat (2014)

europeheat-2017_fortable.jpg' width = 450 height = 253 > Extreme Heat — Europe (2017) https://wwa.climatecentral.org/analyses/europe-heat-june-2017/

usheat-2017_fortable.jpg' width = 450 height = 253 > U.S. Heat (Feb. 2017)

australiaheat_fortable.jpg'>' width = 450 height = 253 > Australia Heat (Feb. 2017) europecold-2017_fortable.jpg' width = 450 height = 253 > SE Europe Cold (Jan. 2017) somalia_fortable.jpg' width = 450 height = 253 > Somalia Drought (2016-2017) arcticwarming_fortable.jpg' width = 450 height = 253 > North Pole (Nov – Dec, 2016) usfreeze-2016_fortable.jpg' width = 450 height = 253 > U.S. Deep Freeze (Dec. 2016) kenya_fortable.jpg' width = 450 height = 253 > Kenya Drought (2016) louisianafloods_fortable.jpg' width = 450 height = 253 > Louisiana Downpours (August 2016) germanfloods_fortable1.jpg' width = 450 height = 253 > European Rainstorms (May 2016) indiaheatwave-2016_fortable.jpg' width = 450 height = 253 > India Heat Wave (2016) coralbleaching_fortable.jpg' width = 450 height = 253 > Great Barrier Reef (March 2016) desmondflooding_croppedfortable.jpg' width = 450 height = 253 > UK’s Storm Desmond (Dec. 2015) chennaifloods_fortable.jpg' width = 450 height = 253 > Chennai Floods (December 2015) 2015attribution_f_equiv.jpg' width = 450 height = 253 > Hottest Year on Record (Dec. 2015) 2015attribution_europeanheatwave_observed_map.jpg' width = 450 height = 253 > European Heat Wave (July 2015) ethiopiadrought-2015_fortable.jpg' width = 450 height = 253 > Ethiopia Drought (2015)

wwa-drought_oxfam-flickr.jpg' width = 450 height = 253 > Western Drought (ongoing) wwa-brazildrought_aduarte-flickr_croppedfortable.jpg' width = 450 height = 253 > Southeast Brazil Drought (2014-2015) 2014attribution_eurogfx_europe.jpg' width = 450 height = 253 > Record European Heat (2014)