Why has the UK’s wintery weather stuck around for so long this year? The question’s attracted a good deal of media attention recently, with claims the Met Office has called a rapid response meeting of experts, to get to grips with the question of whether melting Arctic sea ice could be skewing the British weather.
Unusually low temperatures this spring have had many media outlets asking whether climate change could be causing the prolonged winter weather. In an interview for ITV news, the Met Office’s Julia Slingo said scientists need to understand any possible link ” as a matter of urgency“.
ITV suggested the Met Office had convened a “meeting of top experts from around the world”, with the Daily Mail claiming an “emergency meeting” had been called. The Met Office has played down this suggestion to us today, but said that it is investigating the issue as part of ongoing research. So how do scientists think climate change and this year’s cold spell could be linked?
A meandering jet stream
Dr Jennifer Francis, polar scientist at Rutgers University, told us how the Arctic could be involved. Temperatures are rising faster in the Arctic than at lower latitudes – known as Arctic amplification. Because of this, the temperature difference between the frozen north and the more temperate mid-latitudes is decreasing. Losing reflective sea ice speeds up Arctic warming – what’s known as a positive feedback.
The suggestion is that these changes can weaken the jet stream – a stream of fast-flowing air in the atmosphere – which could then start to move about more. This could allow cold Arctic air to reach further south, over mid-latitude countries like the UK. Combined, this means wintery conditions could stay longer in one place.
This is a relatively new area of research and the precise mechanism is far from settled. But it is a topic of very current research, and the idea that there might be a link between the Arctic and UK weather appears to be gaining scientific support.
The Met Office told us it’s holding an “informal workshop” in the next two to three months on the potential influence of the changing Arctic on mid-latitude weather systems. The workshop will be for leading UK scientists plus several international experts.
A spokesperson told us the Met Office’s views on Arctic amplification:
“haven’t changed from the position we’ve held for some time – namely that it’s an area of ongoing research but preliminary evidence suggests there may be a link between low sea-ice extent and cold winters.”
With any area of scientific research – but particularly emerging ones – there remains some degree of uncertainty. As Professor Charles Greene from Cornell University told us:
“Nothing is ever entirely certain in science; rather we deal with probabilities. The Earth’s climate system is changing so rapidly that it is hard to achieve the statistical level of confidence that scientists would prefer because we don’t have the long time series of data needed to say things with 90 or 95% confidence.”
And there’s more to UK weather than just the jet stream. So while scientists are making progress in working out how climate change could influence the odds of abnormal weather, it would be unwise to try to attribute one year’s events to a single cause. For example, the Met Office’s official blog explains:
“Changes in sea surface temperatures due to natural cycles may be playing a part, but there is more research to be done before anyone can establish how big a role they play.”
Matter of urgency
Although the UK’s cold weather is seemingly on its way out, it’s important that scientists get a better handle on how far climate change could be influencing things, to be better prepared in the future. As Green tells us:
“Global warming has increased the loss of summer sea ice in the Arctic, which has altered atmospheric conditions in a manner that stacks the deck in favor of more severe winter outbreaks …I think that the probabilities are high enough that society should be very concerned that we are altering our winter weather patterns in a substantive way.”
Climate scientists have been speculating about how climate change could influence UK weather long before this year’s cold spell. But given the UK’s notoriously complicated weather patterns, teasing out how much of what we’re seeing is down to natural variability and how much could be influenced by greenhouse gases is likely to be a tough task.