UK flooding & climate change

February 18, 2014
by phil

“It is fair to say this is consistent with what we think about climate change and it’s fair to say that the scale of the impacts will have been exacerbated by climate change.”Kevin Anderson (BBC Newsnight, 17 February 2014)

Is there a link?

A week ago most newspaper reports on the exceptional run of storms in the UK made no mention of climate change. A week later, a new analysis by Carbon Brief shows that the proportion of flooding stories that include a mention of climate change doubled from 7% to 15%. The researchers also found that stories discussing the link between the two were getting greater prominence – including front page leads in The Guardian, The Observer, New Statesman and The Spectator.

While it’s good that a link is being made more frequently, there are still those (including many MPs and professional deniers and dismissers) who continue to exploit apparent equivocation in scientific statements in order to argue against the need for taking action.

This is the first in a series of two posts which aim to clear the fog. Here we present evidence for the clear link between the flooding and climate change. The second post will explore the extent to which extreme weather events can be attributed to climate change.

Flooding is a long-predicted climate change impact for the UK

Twelve years ago the UK Climate Impacts Project (UKCIP) 2002 report Climate Change Scenarios for the United Kingdom ran a list of 15 expected changes in which they expressed high confidence, including:
  • winter precipitation increases
  • winter precipitation intensity increases
  • sea level rises
  • extremes of sea level become more frequent
These findings were in turn similar to the predictions made by UKCIP four years earlier in 1998. So we have been aware of the general trends predicted for the UK due to man-made climate change for at least fifteen years.

“The biggest challenge to the British Isles from climate change is flooding”

In 2004 the government Chief Scientist (2000-2008), Sir David King, presented a report he had commissioned to government on how best to manage the increased risk of flooding and coastal erosion over the coming decades. The report used the UKCIP 2002 findings as its starting point and confirmed (alongside its other recommendations):

  • “Under every scenario considered, flooding would increase substantially by the 2080s”
  • “Reducing global greenhouse-gas emissions would substantially help to manage future risks”

Speaking on BBC Newsnight on 12th February, King explained that “the biggest challenge to the British Isles from climate change is flooding.” The only thing that surprised him about the scale of the recent flooding in the UK was that such dramatic impacts were happening so soon:

Jeremy Paxman: Are you surprised by these floods?

Sir David King: I am surprised. I think it’s all happened a bit earlier than I would have expected. In the sense that we put in a report to government back in 2004 on flood and coastal defences and in that report we used the best that climate science could produce for us to anticipate what the challenges would be for the British Isles. The biggest challenge to the British Isles from climate change is flooding. So we set it out in some detail. It was an enormous piece of work. And the net result was that we were saying within in 20 years this sort of thing would be happening. So yes, it’s happening a bit more quickly than we expected.

JP: So you predicted it but the timescale has collapsed.

SDK: Right.

The warnings given by the 2004 Foresight report were, if anything, made more severe in a 2008 update.

Basic physics

This month the Met Office issued a briefing on the UK’s recent floods and storms which concluded (p.3): “There is an increasing body of evidence that extreme daily rainfall rates are becoming more intense, and that the rate of increase is consistent with what is expected from fundamental physics. There is no evidence to counter the basic premise that a warmer world will lead to more intense daily and hourly heavy rain events.”

As James Hansen puts it in his book Storms of My Grandchildren: “Global warming does increase the intensity of droughts and heat waves, and thus the area of forest fires. However, because a warmer atmosphere holds more water vapour, global warming must also increase the intensity of the other extreme of the hydrologic cycle – meaning heavier rains, more extreme floods, and more intense storms driven by latent heat, including thunderstorms, tornadoes, and tropical storms.”

Observations

The world has warmed by 0.8C since pre-industrial times. The observed changes we have seen over this period include: a sea level rise of about about 20 cm; extreme rainfall events in the UK becoming more common (events that were considered to be 1 in 125 day events during the 1960s and 1970s appear to be occurring about once in 85 days now on average – Met Office p.22); and a significant increase in the intensity of the very strong winter cyclones over the mid-latitude North Atlantic – i.e. the path of the recent storms (Met Office, p.21).

Complicating factors

The picture is complicated by the Arctic which is warming twice as fast as the global average. The reduced temperature differential between the polar North and the mid-latitudes appears to be destabilising weather patterns by changing the course and strength of the jet stream and the position of the polar vortex.

The unprecedented feature of the UK floods was the number of storms and the prolonged duration of the storm cluster that led to the wettest January-December since at least records began (248 years). Research by Jennifer Francis and Stephen Vavrus suggests a link between the changes we are seeing in the Arctic and such prolonged weather events.

The future forecast

The UKCIP website currently lists the key ways in which the UK climate is expected to change:
  • higher average temperatures in both summer and winter
  • changes in seasonal rainfall patterns
  • rising sea levels
  • more very hot days and heat waves
  • more intense downpours of rain and
  • higher intensity storms

The severity of these impacts depends on whether or not we start taking urgent action to mitigate climate change as an international community – as explained in my interview with IPPC lead author Pierre Friedlingstein.

Here’s Kevin Anderson, deputy director of the Tyndall Centre on BBC Newsnight last night (17 February 2014):

Victoria Derbyshire: Kevin Anderson, you believe global temperatures will rise by, what? Three, four, five degrees centigrade by the end of the century?

Kevin Anderson: Oh, certainly if we do not reduce our emissions.

VD: Right. What will Britain look like then?

KA: If you talk about 4C rise then we’re talking about at least a metre of sea level rise before the end of the century. And if you put on top of that the increased severity of storms and possibly increased frequency of storms as well…

VD: What will Britain be like if that happens?

KA: It will be a very different shape. It doesn’t matter how much dredging you do in the Somerset Levels you will not be able to keep that part of the country…

VD: The Somerset Levels wouldn’t exist?

KA: They simply wouldn’t exist, but nor would probably large parts around the Thames indeed as well. So the shape of the UK map… A lot of East Anglia would go, many of the islands would have gone off the north of Scotland, Humberside. Many parts of the UK would suffer and we would see major problems with trying to rehouse people. At the same time, remember this is a global problem, we’d be having problems with the imports of our food from elsewhere in the world. Our energy infrastructure is not designed for this, we still have an infrastructure that is very Victorian…

Finally, Carbon Brief today extract some key messages from the leaked forthcoming IPCC Working Group II report – on the future impacts of climate change – that relate to the likely impact on the UK from flooding under various emissions scenarios.

Update: A day after we published this post, the the Committee on Climate Change published its view on the link between UK floods and climate change which squares very closely with our own.

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