Climate change could lead to increased extreme rainfall, flooding - study

An hour of 30 mm of rain is considered the threshold that triggers flash flood warnings and often leads to flash foods in general.

Lightning strikes over the Mediterranean sea during a rain storm near the city of Ashkelon (photo credit: AMIR COHEN/REUTERS)
Lightning strikes over the Mediterranean sea during a rain storm near the city of Ashkelon
(photo credit: AMIR COHEN/REUTERS)

Extreme rainfall of the future could be more severe and frequent than previously thought, new data reveals.

Using data gained from new climate models and the latest IPCC assessment, experts have been able to look at the severe flooding seen throughout the world in 2021 and project expectations for the future.

And these expectations are not good.

Currently, the Scottish city of Glasgow, which is hosting the UN climate conference known as COP26, sees occasional days of rain with 30 mm or more of rainfall an hour. However, assuming temperatures rise by around 3°C by 2070, these extreme rainfalls in Glasgow could be 3.5 times as likely, and 2.5 times as likely in London. 

An hour of 30 mm of rain is considered the threshold that triggers flash flood warnings and often leads to flash foods in general. With rainy days like this being more likely, it seems flash floods could also become more likely in the future as well.

Nahariya man drowns in flood while attempting to save others (credit: NOAM FLAKSA/TPS)Nahariya man drowns in flood while attempting to save others (credit: NOAM FLAKSA/TPS)

This projected temperature rise is more than the expected outcome of COP26, but it is important to use these plausible high emissions for long-term risk assessment. This is especially true regarding recent flood events, which have shown that the issue is more urgent than previously thought.

In the UK, for example, the 10 wettest years on record have all been since 2000.

Devastating floods were seen in the summer of 2021 in Central Europe, the London underground and Zhegzhou, China.

During the European flooding, Western Europe saw in some parts two months' worth of rain over the course of just two days.

This is also in line with the recent climate models showing slower-moving storms. These can lead to a high accumulation of rainfall, meaning it can rain harder for longer.

According to a study by the Met Office and Newcastle University, these slow-moving storms will be 14 times more frequent in Europe by 2100, should global temperatures rise by 4.3°C. 

“Recent developments in high-resolution climate projections are letting us examine changes in future extreme rainfall in unprecedented detail,” Met Office climate scientist Prof. Lizzie Kendon said in a statement

“We’re seeing that extreme rainfall events are being made both more frequent and more intense as a consequence of human-induced climate change. Recent flooding events around the world show the devastation that intense rainfall can cause. By reducing our greenhouse gas emissions, the worst impacts can be avoided, but organizations and individuals need to be resilient to the changes in our weather that we’re already committed to.”

“Climate change is no longer just an issue about the future,” explained Prof. Peter Scott, science fellow in climate attribution at the Met Office Hadley Centre. 

“With the atmosphere having already warmed by around 1°C it can hold roughly 7% more moisture than it would have in the pre-industrial period, leading to more extreme rainfall events. As well as the chances of more extreme rainfall in the future we’re seeing the influence of climate change on the weather we’re experiencing now.”