Welcome to the Climate Radio archive! 2014 promises to be a pivotal and exciting year in the transition to our low carbon future. This year our contribution is likely to be predominantly in the form of print media. We will be posting developments here at the Climate Radio archive, so stayed tuned! In the meantime, Climate Radio’s monthly shows for 2013 can be found here. As can our additional special programmes including new economics foundation fellow Andrew Simm’s keynote speech “Seeking Goodland”, coverage of the Reclaim The Power protest camp against fracking in Balcombe and an audio document of the Two Degrees festival of climate arts-activism. Thanks to Artists Project Earth, Resonance FM and New Internationalist for their support in 2013.
“We are in danger of losing sight of some glaringly obvious truths about this exceptionally wet and stormy winter.” - Phil Rothwell, Head of Flood Risk Policy at the UK Environment Agency until December 2013
In the last post we looked at the clear link between climate change and the UK flooding. Here we discuss what we know and what we don’t know about the extent to which you can blame (or attribute) the exceptional run of storms that led to the widespread flooding, on (or to) climate change.
All weather events have a climate contribution
As Kevin Trenberth of the National Center for Atmospheric Research argues in Climatic Change, asking whether a particular weather event was “caused” by climate change is the wrong question:
All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be (…) no events are ’caused by climate change’ or global warming, but all events have a contribution.
Discerning the size of this contribution is the task of the science of attribution, a science which is still young and can’t tell us very much with certainty. The challenge is discerning how much is natural variability and how much is due to manmade climate change. As the World Meteorological Association’s report 2001-2010: A Decade of Climate Extremes puts it:
Owing to the naturally high internal variability of the climate system, however, it is still difficult to assess in a systematic way the degree and amount of climate-change influence on a single observed event.
Methodologically, the science is complicated and time consuming. The approach that many attribution studies take is to compare a long data sample of real world weather events against the results you get when you run a computer climate model without any human-induced climate change.
Attribution of trends is easier than for events
It’s easier to link climate change to trends than it is to specific events lying outside what is expected. Take for example this extract from an interview with the lead editor on a 2012 collection of studies of extreme events, concerning the record low summer Arctic sea ice in 2012.
Rebecca Lindsey: Of all the events that scientists chose to analyze, the ones that look for a human fingerprint in the record low Arctic sea ice extent in September 2012 might puzzle people. Is there still uncertainty that human-caused warming is the primary cause of Arctic sea ice loss?
Thomas Peterson: There’s still uncertainty about the speed with which Arctic sea ice will be melting in the future and when we will have an ice-free Arctic Ocean during the summer. We can see the long-term trends, and that’s obviously related to climate change. But we also see some major dips, like in 2012, when you have record low event. So what they’re trying to figure out is, even with the long-term trend, what caused that particular year to be extremely low. That’s relevant if you are looking at projections in the future. If this record-low year was due solely to global warming, that would alter one’s expectations of how quickly one should expect an ice-free Arctic Ocean.
RL: So you’re talking about the difference between the influence of human-caused climate change on a long-term trend versus its influence on a specific event?
TP: Yes, there’s attribution of change and attribution of events.
What does attribution science have to say about the UK floods and manmade climate change?
The head of the Met Office’s Climate Monitoring and Attribution team, Peter Stott, has written about what attribution studies are able to say about the link between climate change and the recent UK flooding and the answer is: ‘nothing – there have been no formal attribution studies, but we’ve got some great new models so maybe we’ll have something to tell you in the future.’
As Stott explains, the complicating factors are our lack of understanding about how and why the jet stream is changing and what caused the run of storms to be unusually persistent:
The current exceptionally wet and stormy British winter provides a particularly challenging test case for attribution science. A disturbed and stronger than usual jet stream has brought a sequence of intense storms on a more southerly track than usual.
(…) But an unusual feature of the weather this winter has been the persistence of weather patterns, with storms lining up across the Atlantic to batter the country one after the other.
At present we don’t know how different drivers within the global circulation have affected this sequence of storms, nor do we know for sure if our current generation of climate models are able to calculate the relevant processes reliably enough to make an accurate calculation of the changed risk of such events.
Something that may clear up the issue around the unusual persistence of the storms is research by Jennifer Francis and Stephen Vavrus which has suggested a link between the changes we are seeing in the Arctic (something we explored in this edition of Climate Radio) and an apparent recent pattern of prolonged weather events. This is new science over which there is still some debate. Listen to this conversation between Jennifer Francis and Kevin Trenberth to get an idea of the current state of the debate:
Climate deniers like to pounce on scientific uncertainty as support for their position. Listen to anti-climate action campaigner Nigel Lawson doing precisely this in the context of the UK floods on the agenda-setting BBC Radio 4 Today programme. However, a lack of understanding around a new and emerging situation is simply that. It does nothing to undermine what we already know from modelling, basic physics and observation.
What we know already: “the scale of the impacts will have been exacerbated by climate change”
For now, scientists have made clear statements on how manmade climate change has made the UK flooding worse due to both sea level rise and a greater risk of intense rainfall from increased moisture in the air:
We know that the sea level rise that has already gone on because the oceans have warmed, and we know therefore that some of the impact of Sandy in New York or some of the impacts in Haiyan [in the Philippines], or the impacts we’re seeing now [in the UK] are partly due to the increased sea level rise. So it makes the situation worse even if the overall event is not a climate change event.
and here’s Peter Stott again:
It is clear that global warming has led to an increase in moisture in the atmosphere – with about four per cent more moisture over the oceans than in the 1970s – which means that when conditions are favourable to the formation of storms there is a greater risk of intense rainfall.
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
- winter precipitation increases
- winter precipitation intensity increases
- sea level rises
- extremes of sea level become more frequent
“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.
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.”
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).
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
- 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.
Now published at Ceasefire Magazine.
In 2011 Anjali Appadurai gave a powerful speech at the UN climate talks on behalf of the youth of the world. She hounded negotiators for their lack of ambition, broken pledges and betrayal of future generations. In an exclusive interview with Ceasefire, she reflects on the incremental progress made in Warsaw in December, why a colonial attitude and corporate interests are holding us back, and on the solutions and strategies that can take us forward. Appadurai continues to track the negotiations with Third World Network and Earth in Brackets. You can view her 2013 TEDx talk and follow her on Twitter.
Phil England (PE): What’s at stake at the UN climate talks?
Anjali Appadurai (AA): With climate change I think we’ve really underestimated the gravity of the issue. The continued reports coming out from the Intergovernmental Panel on Climate Change are slowly helping to cement the idea that this has more consequences for the global community than any other problem we’ve tried to solve at the UN. What’s at stake is a global agreement which would not solve climate change in itself but would provide a legal framework within which solutions could be created and implemented.
PE: What is your overall sense of the progress made at the latest round of talks in Warsaw in December?
Videos of all the presentations given at the Radical Emissions Reductions Conference in December at the Royal Society are now available here. Here are the framework-setting opening speeches by Corrine Le Quere and Kevin Anderson, followed by Naomi Klein‘s keynote speech.
Here’s our interview with Pierre Friedlingstein – one of the lead authors on the latest Intergovernmental Panel on Climate Change (IPCC) report – which we were unable to fit into our October programme on Solutions. Here he explains some of the key findings of the IPCC’s fifth assessment report on the physical science of climate change.