Anthropogenic contribution to global occurrence of heavy-precipitation and high-temperature extremes

…more than half of the hot extremes worldwide and nearly a fifth of precipitation extremes can be attributed to global warming. Not one of these events is solely the direct result of warming, but warming increases their frequency. And the less common and more extreme the hot extreme or heavy rainfall event, the more this can be attributed to a man-made contribution.

Dr. Erich Fischer, ETH Zürich

With every degree of warming it is the rarest and the most extreme events—and thereby the ones with typically the highest socio-economic impacts—for which the largest fraction is due to human-induced greenhouse gas emissions

Erich Fischer and Reto Knutti, ETH Zürich

• Applies a similar framework as past studies attributing specific heatwave and heavy precipitation events to human-caused climate change but estimates what fraction of all globally occurring heavy precipitation and hot extremes is attributable to warming
• Shows that at the present-day warming of 0.85 °C about 18% of the moderate daily precipitation extremes over land are attributable to the observed temperature increase since pre-industrial times, which in turn primarily results from human influence
• Finds that for 2°C of warming, the fraction of precipitation extremes attributable to human influence rises to about 40%.
• Finds that today about 75% of the moderate daily hot extremes over land are attributable to warming
• Holds it is the most rare and extreme events for which the largest fraction is anthropogenic, and that contribution increases nonlinearly with further warming
• Asserts the approach introduced is robust owing to its global perspective, less sensitive to model biases than alternative methods and informative for mitigation policy, and thereby complementary to single-event attribution