New research method reveals close ties between extreme floods and rising temperatures

The intensity of extreme water cycle events such as floods and droughts correlates with global warming, a new study has shown. Researchers used satellite observations to quantify and rank more than a thousand extreme weather events over the last 20 years that previously defied easy measurement. The results from the novel method – known as GRACE-FO – agreed with a recent report released by the Intergovernmental Panel on Climate Change (IPCC).

The report, published by Nature Water journal on 13 March, showed that events such as drought and flooding have increased as global temperatures have risen. Co-author Matthew Rodell of NASA told Agence France-Presse (AFP) that:

Warm air increases evaporation so that more water is lost during droughts, and warm air also holds and transports more moisture, increasing precipitation during wet events. So what we are seeing – greater intensity of extreme wet and dry events as the world warms – makes sense.

Since 2015, the frequency of the highest category extreme events has increased to four per year. The study said that the previous 13 years had three such events per year.

Nonetheless, the way in which the pace of global warming closely mirrored the intensity of water cycle disruption events surprised the researchers. The impact was even stronger than the naturally occurring El Niño and La Niña weather phenomena.

Prepare better for future floods and droughts

The findings leave little doubt that increasing temperatures will cause more frequent, widespread and severe droughts and precipitation events in the future. Earth’s surface has warmed, on average, 1.2C since the late 19th century. With current governmental policies worldwide, it is on track to heat up 2.8C above that benchmark by 2100.

The largest extreme event of the past 20 years was a sustained deluge over central Africa that “dwarfed” all the others measured. It caused Lake Victoria to rise by over a metre. Furthermore, it was still ongoing in 2021 when the study concluded. The water level rise led to severe floods in Kenya, Uganda and Tanzania.

Roughly a third of the top 30 wet and dry events globally occurred in South America. More broadly, the correlations were particularly strong in tropical climates. The most intense dry event registered happened in the Amazon during 2016, the hottest year on record.

Extreme droughts and floods are ranked as some of the world’s worst disasters. They have huge impacts on economies, societies, and agriculture. Nature Water study author Matthew Rodell told AFP:

The conclusion of this study suggests that preparation and adaptation will be that much more important in the future.

The Nature Water research offered concrete support for the IPCC’s most recent assessment report, published in August 2021. It found that the severity of extreme water cycle events is increasing. Regarding the IPCC report, PBS reported that:

it is clear that the severity of climate change impacts are closely linked to greenhouse gas emissions: Reducing emissions will reduce impacts. Every fraction of a degree matters.

Featured image via xchipsmore and thelivingtr/Wikimedia Commons, resized to 770*403

Additional reporting by Agence France-Presse