Extreme weather events, for science it is man’s fault

According to the Climate Brief report, which analyzed 504 studies dedicated to single extreme events, 71% were caused or exacerbated by human action. Hot record? Some extreme temperatures would be impossible without our influence

Heat waves, floods, droughts: human hands are behind these extreme events. At least in most cases. And this time it is science that agrees on the attribution of blame. A new study by Climate Brief researchers collected 504 studies dedicated to single extreme events to understand which and how many of these could be attributable to human-induced climate change, and the result is that 71% of these 504 extreme weather events were found to have been caused or exacerbated by human activities.

Notably, of the 152 extreme heat events assessed by scientists, 93% were made more likely or more severe by humans, as were 56% of the 126 rain or flood events surveyed, and 68% of the 81 drought events. 9% of climate and weather events have been made less likely or less severe by human activities, meaning that 80% of all events have been impacted by humans. Because from the studies analyzed, only 20% of the events do not show any clearly identifiable human influence.

In short: the scientists concluded that human-caused climate change altered the probability or severity of an extreme weather event in 80% of the cases studied (in 71% it made it more severe or likely and in 9%, less). First published in July 2017, this study represents the fifth annual update of a work that is constantly updated. Interestingly, the first edition of 2017 had identified human responsibility in 68% of the events (in 63% of cases it was made more serious or probable and in 6% less).

Extreme temperatures impossible without human influence

The Carbon Brief attribution map includes studies of 152 extreme heat events, of which 142 (93%) were made more likely or more severe due to climate change. No studies found a heat wave made less severe by climate change, while studies of two events (1%) did not identify any influenza and eight others (5%) were not conclusive.

In recent years, studies have shown that various extreme temperatures would have been impossible or virtually impossible without human influence on the climate. These include the Siberia heatwave of 2020, the Pacific Northwest ‘heat dome’ event of 2021, and Europe’s record summer of 2021.

Heavy rain, floods and droughts

Of the 126 rain or flood events included in the attribution map, 71 (56%) found that human activity made the event more likely or more severe, a much lower percentage than in heat studies. Nineteen studies (15%) found that climate change had made the whole event less likely to occur. Of the remaining heavy rainfall events, studies of 24 (19%) found no evidence of a link to climate change, while 12 (10%) were inconclusive.

Of the 81 drought events and trends considered here, climate change was found to have increased severity or probability by 55 (68%). Moreover, the probability or severity was reduced for one event (1%), while no discernible link with human activity was found for 15 (19%) and 10 (12%) inconclusive.