December 2, 2021

I, Science

The science magazine of Imperial College

The wet weather last winter is likely to be repeated and climate models are showing why ...

This news story was published in the World News section of the Super Science issue (issue 28), as one of the most important science stories of the past few months.

Reservists from 7 Battalion, The Rifles Reinforcing a Dam During Flooding

The chances of heavy winter rainfall on the south of England have increased by 25% since pre-industrial times according to research carried out by a team at the University of Oxford.

Catastrophic floods like those experienced earlier this year are now predicted to happen once every 80 years, rather than once every 100 years, which was the previous estimate.

It’s been widely reported that one reason for last winter’s extreme weather could be man-made global warming. Research presented at the AAAS meeting at Chicago suggested that with more of the Sun’s radiation hitting Earth, comparatively more will hit hot areas within the tropics than will hit more northerly latitudes. That larger difference between the temperature at mid-latitudes and at more northerly latitudes could speed up jet streams that move in a north easterly direction across the Atlantic and Pacific oceans.

Speaking on the extreme weather at the Chicago meeting, Professor Jennifer Francis of Rutgers University in New Jersey said: “We can expect more of the same and we can expect it to happen more frequently.”

The immediate trigger for the UK storms was attributed to unseasonable storms in Indonesia that led to an acceleration of the jet stream across the Pacific. This pushed the warm, wet air further north than it normally goes leading to a ‘polar vortex’ and a harsh winter in the United States with temperatures as low as -26 °C in the Midwest.

It was thought this had a knock on effect for the Gulf Stream over the Atlantic that caused it to move faster and bring with it wave after wave of storms.

The 2013/14 winter was the wettest winter since records began in 1766. If Professor Francis and her research team are correct, these periods of persistent rainfall are likely to stay.


IMAGE: UK Ministry of Defence