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Evidence: extreme weather ‘event attribution’

Extreme weather

(Image: NASA)

How we know if extreme weather is due to climate change: ‘Event Attribution’

Summary

  • ‘Event attribution’ works out what percentage, if any, climate change is responsible for the frequency and scale of extreme weather and other events such as extreme forest fires, melting glaciers, and rapid phenological shifts (plants and animals moving and/or dying out), drought (Fig. 1), and events such as the June 2021 Pacific Northwest heatwave that killed an estimated billion marine animals and over 500 people (US and Canada).
  • If we understand how likely an event occurs because of climate change, versus the internal ‘noise’ of Earth’s climate—natural fluctuations such as El Niño—we can better plan for and help mitigate future climate costs.
  • Insurance underwriters use these tools to help calculate how much you will have to pay for insurance, or to decline insurance; for example if you live in an area at risk from rising sea levels.

For too long, weather’s randomness has kept events such as these from being blamed squarely on climate change… Now, we can specify increased chances for specific events. This extends to forecasts: we can identify the places that are more likely to see wildfires, mudslides and fish die-offs. Such calculations dent both climate denial and a false sense of security. They take away the argument that ‘extreme weather happens anyway, so we don’t need to worry about it’. Extreme weather happens—and these metrics pinpoint what is becoming more likely, by how much and why… Such evidence is also useful for legal proceedings when citizens call corporations or governments to account for their role in climate change.Richard A. Betts

As this is such a diverse field, if you would like to know more about specific events see World Weather Attribution

Event attribution for New Zealand is undertaken by NIWA and funded by the Deep South National Science Challenge.

Carbon Brief also regularly archives ‘science explainer’ event-attribution articles, including research on New Zealand’s vanishing glaciers. and patterns of extreme rainfall and drought (Fig. 3).

Fig. 1: Local anomalies in rainfall (top) and the “climate moisture index” (CMI; bottom) from 1860 to 2019 across the globe. Brown shows drying while green shows increases in rainfall and moisture. (Image: Bonfils et al.)

“More than 300 peer-reviewed studies have been published since 2000, that examine weather extremes around the world, from wildfires in Alaska (pdf) and hurricanes in the Caribbean to flooding in France and heatwaves in China. The result is mounting evidence that human activity is raising the risk of some types of extreme weather, especially those linked to heat.” – Carbon Brief

Fig. 2: Click on the image to be taken to the list of ‘event attribution’ research papers (Carbon Brief).
Fig. 3: How climate change affects extreme weather around the world. Click on the Carbon Brief map to see other countries and zero in on specific events.

References and further reading