The Mail on Sunday has claimed two high profile Met Office scientists disagree with each other on what’s behind the recent exceptional weather in the UK. But the scientists involved say the newspaper has got it wrong, and that “there is no disagreement.”
This weekend, the Mail On Sunday ran an article by climate skeptic journalist David Rose, entitled ‘No, global warming did NOT cause the storms, says one of the Met Office’s most senior experts’.
The piece quotes Professor Mat Collins, a climate scientist at the University of Exeter who is also affiliated with the Met Office. It suggests Collins disagrees with the Met Office’s chief scientist, Dame Professor Julia Slingo, over the link between climate change and the recent wild weather. The piece says:
“One of the Met Office’s most senior experts yesterday made a dramatic intervention in the climate change debate by insisting there is no link between the storms that have battered Britain and global warming â?¦ His statement appears to contradict Met Office chief scientist Dame Julia Slingo”.
But yesterday, Collins and the Met Office issued a joint statement dismissing the interpretation, saying “this is not the case and there is no disagreement.”
A warmer, wetter world
Last week, Slingo spoke to journalists ahead of the launch of a Met Office report, authored by her, into what’s behind the recent exceptional weather in the UK. Her comments have been widely reported.
When asked whether she thought the intense recent storms and flooding could be linked to rising temperatures, Slingo responded:
“In a nutshell, while there is no definitive answer for the current weather patterns that we have seen, all the evidence suggests that climate change has a role to play in it.”
Slingo’s comments reflect scientists’ confidence that the extremely heavy rainfall we’re seeing these storms deliver fits in with what scientists expect in a warming world. Over the UK, there’s already evidence that heavy rainfall events are getting more frequent. According to the Met Office, what might have been a 1 in 125 day rainfall event is now more likely to be a 1 in 85 day event.
What would have been a 1 in 125 year rainfall event in the 1960s is now more likely to be a 1 in 85 year event. Source: Met Office report “The recent storms and floods in the UK”.
Basic physics says that a warmer atmosphere can hold more moisture. That means when rain does fall, it tends to fall in heavier bursts. With so much rain in such a short space of time, the ground hasn’t had chance to recover – leading to widespread flooding.
In the Mail on Sunday article, Collins makes the same point:
“Prof Collins made clear that he believes it is likely global warming could lead to higher rainfall totals, because a warmer atmosphere can hold more water.”
And in the Met office statement released yesterday, the Met Office and Collins say:
“What the Met Office report – and indeed the IPCC – does say is that there is increasing evidence that extreme daily rainfall rates are becoming more intense â?¦ [W]hen conditions are favourable to the formation of storms there is a greater risk of intense rainfall. This is where climate change has a role to play in this year’s flooding.”
So on the extreme amounts of rainfall we’ve been seeing, Collins, Slingo and the report she authored agree the evidence points to climate change playing a role.
A “stuck” jet stream
But there’s another factor in the recent flooding. On top of the extreme amount of rain we’ve seen, there’s the question of ‘why now’? – Why have so many storms have hit the UK in quick succession?
On this point, a link with climate change is much less clear – and it’s this that Collins is speaking about in the Mail on Sunday piece. The article gives Collins’s explanation for the continued run of storms, saying:
“[Collins told the Mail on Sunday] the storms have been driven by the jet stream – the high-speed current of air that girdles the globe – which has been ‘stuck’ further south than usual”
This video from the BBC’s David Shukman gives a good explanation of how changes in the jet stream link up with the weather we’ve seen in the UK.
Is the unusual behaviour of the jet stream down to climate change? The Mail article quotes Collins as saying:
“[There is] no evidence that global warming can cause the jet stream to get stuck in the way it has this winter. If this is due to climate change, it is outside our knowledge.’
While the Mail on Sunday piece argues Collins’s comment “appears to contradict Met Office chief scientist Dame Professor Julia Slingo”, the Met Office report which Slingo authored makes a very similar point. It says there is not enough evidence yet to say whether or not a more southerly-than-usual jet stream could be a consequence of climate change, saying:
“This is a critical question because it raises the possibility that disruption of our usual weather patterns may be how climate change manifests itself. The Met Office is now actively researching the best way to detect changes in the dynamics of the jet stream.”
Yesterday’s statement from Collins reiterates this point:
“[L]ow confidence remains in projecting changes in Northern Hemisphere storm tracks, especially for the North Atlantic basin. This is the basis for Prof Collins’ comment and means that we are not sure, yet, how the features that bring storms across the Atlantic to the UK – the jet-stream and storm track – might be impacted by climate change.”
In other words, it’s work in progress.
Overstating the link?
So do Slingo’s comments suggest a stronger connection between climate change and our recent weather than the evidence suggests?
At the moment, it’s beyond scientific understanding of extreme weather to know exactly what the contribution from climate change has been to the recent flooding, or any particular weather event. It’s possible that on a planet that wasn’t warming, this particular run of flooding could have reached the same proportions simply by chance.
But people who work in climate science usually talk about the weight of evidence, not definitive links. The science on the jet stream’s behaviour may be inconclusive, but there is already ample evidence pointing to the fact that climate change increases the odds of seeing extreme conditions when storms do hit – and the shift towards heavier rain we’re already seeing in the UK fits that pattern.
In summary, neither the Met Office nor Professor Collins argue the unusually long sequence of storms we’ve seen in the UK is definitely down to climate change.
But Collins, Slingo, the report she authored all agree that the increasingly heavy rainfall the storms have delivered – and the heightened flood risk – fits in with what scientists expect as the climate changes.
Distinguishing between climate change’s impact on different elements of what we’re seeing across the UK – the succession of storms, the heavy rainfall and the widespread flooding – is difficult enough without suggesting controversy between scientists where there isn’t any.