Future extreme rainfall more extreme than first thought

The impacts of extreme rainfall could be more frequent and severe than had previously been thought at the last UN climate conference, COP25, two years ago in Madrid as reported in this Met Office article.

A new generation of climate models and the latest IPCC assessment (AR6) have provided a new light to look at the recent catastrophic floods seen across the world in the last year and what could be expected in the future.

In a stark example, new calculations using a high emissions scenario with around 3°C of warming by 2070 show that

• In Glasgow, where COP26 is being hosted, the number of days where 30mm of rain or more is recorded in an hour could be 3.5 times more likely by the 2070s compared with the 1990s.

• In London 30mm/hr could be 2.5 times more likely.

30mm of rain in one hour is a threshold which is typically used to trigger flash flood warnings.

These results suggest a big increase in the frequency of flash flood-producing rainfall events.

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