Warming 'worst case' must be considered say experts

By Matt McGrath
Environment correspondent, BBC News

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image captionClimate change may lead to crop failures and food shortages later this century

Climate change risks should be assessed in the same way as threats to national security or public health according to a new report.

For too long the world has seen rising temperatures as a problem of predicting long range weather forecasts.

The authors says that that leaders must focus on the 'worst case scenarios' and how likely they are to occur.

The report has been compiled by an international group of scientists and experts in risk.

In a foreword to the new study, UK foreign minister Baroness Anelay says that previous responses to the threat of climate change have been far too narrow.

"When we think about keeping our country safe, we always consider the worst case scenarios. That is what guides our policies on nuclear non-proliferation, counter-terrorism, and conflict prevention. We have to think about climate change the same way," she said.

Systemic risks

The report underlines, once again, the direct risks that warming poses. It says that at current rates of carbon emissions, a temperature rise of 4 degrees C is "as likely as not" by 2150.

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image captionThe authors warn that climate change could lead increased migration and political instability

This would lead to significant impacts with lethal levels of heat stress, drought and crop failures among a host of other negatives.

But the report goes on to stress that the biggest threats of climate change may come from what are termed "systemic risks".

The study says that these come from the interactions of people, markets and governments.

For instance, climate change may significantly increase the risk of extreme events impacting food production in the second half of this century.

"If policy and market responses amplify rather than mitigate the shock," the report says, "a plausible worst-case scenario in the present day could produce unprecedented price spikes on the global market, with a trebling of the prices of the worst affected grains."

The report also warns that the security implications of high levels of warming are considerable. Growing populations competing for resources could threaten the stability of countries that are currently considered developed.

Migration, the authors warn, could become "more of a necessity than a choice".

Politicians needed to consider the bigger picture, said Fiona Morrison, from the Institute and Faculty of Actuaries, a co-sponsor of the report.

"One of the most important goals of climate change policy should be to recognise the possibility of very bad outcomes and a full risk assessment of all possibilities is the best way to achieve this. As actuaries, we see good decisions as being based on exploring difficult scenarios and using this information to mitigate risk."

Commissioned by the UK Foreign Office the authors include Sir David King, the UK Foreign Secretary's Special Representative for Climate Change and leading members of US and Chinese scientific committees along with experts in risk in energy, finance and military issues.

Campaigners and environmentalists welcomed the report as a useful contribution, saying they believed it would help put pressure on politicians to deliver a new global deal by the end of this year, that would limit warming to 2 degrees C above pre-industrial levels.

"All countries need to better understand the potential consequences for their national security and prosperity of failing to meet the 2 degree C goal," said Nick Mabey from environmental think tank E3G.

"This will require robust national climate risk management regimes to be built in the years after Paris if we are to see the additional action needed to maintain a climate that can deliver global security and prosperity."

Follow Matt on Twitter @mattmcgrathbbc.

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