World Weather Attribution Explained

World Weather Attribution is an academic collaboration studying extreme event attribution, calculations of the impact of climate change on extreme meteorological events such as heat waves, droughts, and storms. When an extreme event occurs, the project computes the likelihood that the occurrence, intensity, and duration of the event was due to climate change. The project specializes in producing reports rapidly, while news of the event is still fresh.^{[1] [2] [3]}

World Weather Attribution was founded in 2014 by climatologists Friederike Otto, who continues as leader, and Geert Jan van Oldenborgh.^[4] Participating institutions are Imperial College London, the Royal Netherlands Meteorological Institute, Laboratoire des sciences du climat et de l'environnement, Princeton University, the U.S. National Center for Atmospheric Research, ETH Zurich, IIT Delhi, and climate impact specialists at the Red Cross / Red Crescent Climate Centre.^[5]

The WWA response to an extreme meteorological event has three parts:^{[1] [6]}

• Define the event: the geographic region affected, which weather parameters are of interest.
• Gather historical data: weather data from the region from 1950 to the present. From this historical data statistics on normal and extreme weather patterns for the locale can be computed.
• Simulate the event many times with computer models, comparing simulations with present-day greenhouse gas conditions against previous greenhouse-gas conditions.

Results are synthesized into a report and published first rapidly, then eventually through the scientific review process.

Example incidents

The following are examples of extreme cold, flood, heat, and drought events that have been studied by WWA.

• An unusual weather pattern which froze vineyards and other crops in France in spring 2021^[7] was 60% more likely due to climate change.^[8]
• Floods in Nigeria and neighboring areas in 2022 were rendered more likely and more intense due to climate change. WWA modeled the June to September rainfall in the Lake Chad and lower Niger river catchment areas, looking at total rainfall and intense rain weeks.^{[9] [10]}
• The 2022 heat wave in India and Pakistan was rendered 30 times more likely and more intense due to climate change.^{[11] [12]}
• A several year draught contributing to famine in Madagascar in 2021 was likely not caused by climate change. WWA studied rainfall in southern Madagascar for the two-year period ending June 2021, concluding that the observed drought had a 1 in 135 chance of occurring, which was only slightly affected by climate change.^{[13] [14]}

Notes and References

1. News: Roston . Eric . Gu . Jackie . July 19, 2022 . Is the Heat Wave Caused By Climate Change? This Is What Scientists Say . Bloomberg News . 2022-11-17.
2. News: Hayhoe . Katherine . Otto . Friederike . August 17, 2021 . What Cutting-Edge Science Can Tell Us About Extreme Weather . New York Times . 2022-11-17.
3. News: October 22, 2021 . The climate project that changed how we understand extreme weather . . . 2022-11-25.
4. News: Fountain . Henry . October 22, 2021 . Geert Jan van Oldenborgh, 59, Dies; Linked Weather Disasters to Climate Change . . 2022-11-17.
5. Web site: About World Weather Attribution initiative . World Weather Attribution . 2022-11-17.
6. van Oldenborgh . G.J. . van der Wiel . K. . Kew . S. . etal . Pathways and pitfalls in extreme event attribution . Climatic Change . 166 . 13 . 2021 . 13 . 2022-11-17 . Springer. 10.1007/s10584-021-03071-7 . 2021ClCh..166...13V . 234099522 . 10044/1/92062 . free .
7. News: Noack . Rick . April 26, 2021 . French vineyards devastated by April frost that followed unusually warm March . Washington Post . 2022-11-25.
8. June 18, 2021 . Climate change increased the likelihood of damaging frosts from the French April 2021 cold wave by about 60% . Government of France, Commissariat à l’énergie atomique et aux énergies alternatives . 2022-11-25 . en.
9. News: Wanjohi . Kabukuru . November 16, 2022 . Nigeria floods 80 times more likely with climate change . 2022-11-25 . . en.
10. November 16, 2022 . Climate change exacerbated heavy rainfall leading to large scale flooding in highly vulnerable communities in West Africa . World Weather Attribution . 2022-11-25.
11. May 26, 2022 . Lottie . Butler . Siobhan . Stack-Maddox . Climate change made deadly heatwave in India and Pakistan 30 times more likely . Imperial College London . 2022-11-25.
12. News: Aniruddha . Ghosal . May 24, 2022 . South Asia's intense heat wave a 'sign of things to come' . 2022-11-25 . . en.
13. News: Zhong . Raymond . December 1, 2021 . 'So Many Dimensions': A Drought Study Underlines the Complexity of Climate . en-US . The New York Times . 2023-01-10 . 0362-4331.
14. December 1, 2021 . Factors other than climate change are the main drivers of recent food insecurity in Southern Madagascar . World Weather Attribution . 2023-01-10.