Climate change: Anthropogenic climate change influenced hurricane rainfall in 2020

Human-induced climate change increased hourly rainfall amounts during the 2020 Atlantic hurricane season by up to 10% compared to pre-industrial levels, suggests a paper published in Nature Communications.

The 2020 hurricane season was one of the most active on record with 30 named storms. Human activities continue to increase the amount of greenhouse gases in the atmosphere, and previous research has shown an increase of more than 1°C in the global average sea surface temperature in 2020 compared to pre-industrial levels. It has been suggested that the increase in surface temperature may have impacted storm intensity and occurrence, however, unravelling the various competing climate effects on storm parameters remains challenging.

Kevin Reed and colleagues modelled the impact of human-induced climate change on sea surface temperatures and suggest that during 2020 surface temperatures rose by 0.4–0.9°C across the Atlantic. They then used a hindcasting (the opposite of forecasting) technique to show how much of the extreme rainfall across the whole of the 2020 North Atlantic hurricane season could be attributed to human-induced sea surface temperature increases. They found that both extreme 3-hourly storm rainfall rates (amount of rainfall in 3 hours) and extreme 3-day accumulated rainfall amounts (amount of rainfall over 3 days) for tropical strength storms were increased by 10% and 5%, respectively, compared to pre-industrial (1850) conditions. The authors also indicate that for hurricane-strength storms the human-induced effect was 11% and 8%, respectively.

The authors suggest their findings demonstrate an anthropogenic signal in rainfall from hurricanes that will have direct consequences for coastal communities.