Climate change means we will have to get used to flooding

 

Professor Nigel Arnell
Tuesday 11 February 2014 20:54
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A resident wades through the floodwater that has swept into Chertsey, which lies just west of London
A resident wades through the floodwater that has swept into Chertsey, which lies just west of London

The political blame-game is in full swing over who is at fault for the current flooding crisis. But ministers debating local dredging operations in Somerset is a sideshow.

It will be a miracle if the winter of 2013-14 does not go down as the wettest on record – and frankly, it is difficult to see what could have been done to prevent massive disruption given the rainfall. But why is this happening?

The immediate answer is that the UK is “stuck” in a weather pattern – a common feature of our climate. But what is uncommon is the exceptional intensity of the rain and waves.

There is a perfect so-called “storm factory” in the Atlantic caused by warm, moist air from the tropics coming up unusually close to the very cold polar air. The jet stream is then acting as a conveyor belt, continually firing these violent weather systems eastwards at us.

The more difficult question is: to what extent is this is down to climate change? On that, the jury is still out.

The latest UN climate report last year was clear that man-made activities over the past 100 years are causing unprecedented climate change. Global temperatures have increased, Arctic sea ice is melting, sea levels are rising and the oceans are getting warmer.

The policymakers asked scientists for consensus and they have it – leaving climate change for future generations to deal with is a phenomenally high-risk option.

Scientists cannot attribute individual weather events to climate change – but coming hot on the heels of major floods in 2007 and 2012, there could well be a link.

We have long been exposed to risk from flooding, but climate change is loading the dice.

Rising sea levels now takes less of a storm surge for coastal flooding to occur than it did a few decades ago. Warmer air can hold more water, and across many parts of the world we have seen more heavy rain over the past few decades.

Most projections of future climate across the UK suggest that we will experience wetter conditions in winter but it is difficult to predict exactly how flood risk will change. What we do know is that relying on historical records is no longer enough, and will likely lead us to underestimate risk.

Climate change affects flood risk differently across the world. In some areas, the flood risk may decrease, because of lower rainfall or perhaps smaller snowmelt floods. But in other areas, risk is likely to increase substantially if greenhouse gas emissions continue to rise, particularly in some densely populated regions such as south Asia.

Overall global exposure to flooding will increase much faster than the projected rises in population and economic growth alone might suggest.

The message for politicians is clear. Even if deep cuts to emissions of greenhouse gases are successful, we will have to live with more floods in Britain.

Once the immediate challenge is over, we need to think deeply about how to manage our flood risk as the climate changes.

Professor Nigel Arnell is Director of the Walker Institute for Climate System Research at the University of Reading

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