The frequency of heavy rainfall in Glasgow could be up to 4.5 times higher by the 2070s compared with the 1990s, according to worrying new climate change data.
The latest climate science indicates extreme rainfall could be more "frequent and severe" than predicted at the last climate conference two years ago in Madrid.
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 addition to the increase in high intensity rainfall, the number of days when 80mm of rain falls in 24 hours could become 4.5 times more likely in Glasgow by 2070 under a high emissions scenario.
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.
Although the high emissions scenario is higher than the expected outcome of COP26, plausible high emissions scenarios like this are routinely used for long term risk assessment.
The calculations used the latest UKCP Local projections.
Flooding events over the past 12 months include devastating flooding in central Europe during summer 2021, flooding of the London underground in July 2021 and in Zhengzhou, China in the same month.
Extreme weather events are nothing new, but the frequency with which they are occurring is changing.
For the UK, five of the 10 wettest years on record have happened since 2000, and the flooding in London in July 2021 is illustrative of the type of event the. UK is likely to see in the future.
Met Office climate scientist, Professor Lizzie Kendon, said: “Recent developments in high resolution climate projections are letting us examine changes in future extreme rainfall in unprecedented detail. 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 organisations and individuals need to be resilient to the changes in our weather that we’re already committed to."
Because of the global warming that’s already taken place, rainfall extremes have already started to change – with one chief saying it's "no longer just an issue about the future."
Science Fellow in Climate Attribution at the Met Office Hadley Centre, Professor Peter Stott, said: “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.”
