With the very worst impacts of the recent storms beginning to tail off, Prime Minister David Cameron waded into the media debate this week by appearing to connect the dots between climate change and recent “abnormal” weather.

Some newspapers suggested Cameron’s comments aren’t backed by the facts, but a close look at what he said shows his comments to be uncontroversial, scientists say.

Stormy weather

The heavy storms hitting Britain in recent weeks attracted a lot of media coverage. Some commented on potential links with climate change, but most left the topic well alone, and one or two flatly dismissed the idea of a connection between the weather the UK is experiencing and any wider climate change.

During Wednesday’s Prime Minister’s questions, Liberal Democrat MP Tim Farron suggested the recent weather in the UK was a “destructive and inevitable consequence, at least in part, of climate change”. Asked whether he agreed, David Cameron replied:

“I agree with you that we are seeing more abnormal weather events. Colleagues across the House can argue about whether that is linked to climate change or not. I very much suspect that it is.”

Soon after, BBC News reported:

“The floods affecting large parts of the country are probably connected to climate change, David Cameron has said”.

While the Guardian headlined:

“David Cameron ‘very much suspects’ climate change is behind recent storms”

Reaction

The media were quick to suggest Cameron’s comments may not sit well with some of his colleagues, who are known to be skeptical about the science of climate change. In particular, the Telegraph and the Independent report that environment Secretary, Owen Paterson, who has previously suggested climate change could have advantages for the UK, “sidestepped” the question of whether he agreed with the Prime Minister.

The Telegraph also published a piece yesterday titled “Prime Minister climate change opinion not backed up by science, says Met Office” However, the Met Office tells us it’s complained about the piece, which presumably doesn’t reflect its views.

So was Cameron right to say what he did?

Risk of heavy rain and flooding set to rise, scientists say

On top of strong winds, a particularly destructive impact of the recent storms has been widespread flooding across the country. By Monday this week, the Met Office had issued flood warning for almost all of the UK and 100 still remain in place across England and Wales.

Flood warnings in place across most of the UK on Monday. Source:  Met Office

Will climate change lead to more scenes like this?

One thing that affects flood risk is the amount of rain that falls when a storm hits. Research suggests rising greenhouse gases have doubled the likelihood of extreme rainfall in Europe and North America. Professor Richard Allan from Reading University explains there’s a fairly simple physical reason for this:

“As temperatures rise, basic physics dictates an increase in the amount of atmospheric moisture, which is the fuel for heavy rainfall events.”

Professor Peter Stott from the Met Office told journalists at a briefing in London today what this increase in atmospheric moisture means for the UK:

“There’s a great deal of variability in UK rainfall but the greater moisture in the atmosphere, which feeds storms when they form â?¦ that means when we get weather patterns conducive to heavy or prolonged rainfall, we can expect the rainfall to be more intense.”

Alongside rising sea levels and houses being built on floodplains, scientists are confident that heavier rainfall events in the future as a result of climate change are likely to increase the risk of flooding. Although Cameron didn’t specifically refer to flooding risk in his answer, he would have been justified had he done so.

On the other hand, had he been implying climate change definitely played a role in the current spell of flooding, the case is less clear cut.

Scientists are keen to point out no single weather event can be definitively linked to climate change, nor can one event be considered representative of what’s happening to the climate in the longer term. Instead, they talk about how climate change is altering the odds of an extreme event occurring.

The Met Office says it’s too soon to tell for sure whether climate change influenced the odds of the recent flooding happening. A spokesperson tells us:

“No attribution study has been carried out on the stormy weather the UK has recently experienced.”

Too early to predict storms

While the link between climate change and heavy rainfall is well-understood, not all types of extreme event are affected by rising temperatures in the same way.

When it comes to knowing how climate change might affect the number of storms, globally or in the UK, the evidence is far from clear. As a recent Met Office News blog puts it:

“Climate models provide a broad range of projections about changes in storm track and frequency of storms. While there’s currently no evidence to suggest that the UK is increasing in storminess, this is an active area of research under the national climate capability.”

It’s important to be clear that the view of the Met Office is there’s no evidence for a link between climate change and more frequent storms. It’s also important to understand what scientists are saying here – no evidence for a link is not the same as evidence there is no link.

Professor Alan Thorpe from the European Centre for Medium Range Weather Forecasts told journalists today:

“It’s a difficult question to work out the effects of climate change on these storms as there are competing processes at play â?¦ we are doing research on it right now â?¦ to look at whether there were trends in storminess during the 20th century â?¦ It’s an important but quite tricky problem.”

While the evidence for heavier rainfall is pretty clear cut, a lot more work is needed before scientists can say one way or the other about storms.

A broader view of extreme weather

Although Cameron was responding to a question about flooding, his answer appears carefully worded to cover all types of “abnormal” weather. And scientists do believe that climate change is leading to an overall increase in weather extremes.

As Professor Rowan Sutton from Reading University told the BBC’s Today Programme:

“[W[hen we look worldwide, and we look at the patterns over a number of years, then the [Intergovernmental Panel on Climate Change] had a very clear statement; human influence on the climate system is clear, and we should not be surprised to see unusual patterns of weather emerging over timescales of decades, as indeed is happening.”

Myles Allen, professor of climate change at Oxford University, told journalists today:

“[The Prime Minister said he] ‘very much suspects a link’ and that’s the sort of nuanced language I would probably use myself â?¦ I would not have used the Telegraph headline â?¦ On that score, my view is that he got the balance about right â?¦ We are seeing more abnormal weather events and [Cameron] did not say – and it would be wrong to say – that every kind of damaging weather event is becoming more likely because of climate change.”

As usual when discussing extreme weather, it’s important to be clear about exactly what’s being talked about.

Distinguishing between storm frequency, rainfall intensity and flooding risk is important when talking about links to climate change – even if it’s a challenging level of detail to fit into PMQs.

But judging by the scientists who’ve spoken about this in the last few days, claims Cameron’s comments are “at odds” with the science are unfounded – this time at least.