There is a reason why the military are so clear-headed about the climate threat, according to Professor John Schellnhuber, a scientist who briefed the UN security council on the issue in February and formerly advised the German chancellor, Angela Merkel.

“The military do not deal with ideology. They cannot afford to: they are responsible for the lives of people and billions of pounds of investment in equipment,” he said. “When the climate change deniers took their stance after the Copenhagen summit in 2009, it is very interesting that the military people were never shaken from the idea that we are about to enter a very difficult period.”

He added: “This danger of the creation of violent conflicts is the strongest argument why we should keep climate change under control, because the international system is not stable, and the slightest thing, like the food riots in the Middle East, could make the whole system explode.”

The military has been quietly making known its concern about the climate threat to security for some time. General Wesley Clark, who commanded the Nato bombing of Yugoslavia during the Kosovo war, said in 2005: “Stopping global warming is not just about saving the environment, it’s about securing America for our children and our children’s children, as well.”

In the same year Chuck Hagel, now Obama’s defence secretary, said: “I don’t think you can separate environmental policy from economic policy or energy policy.”

Morisetti said there was also a direct link between climate change and the military because of the latter’s huge reliance on fossil fuels. “In Afghanistan, where we have had to import all our energy into the country along a single route that has been disrupted, the US military have calculated that for every 24 convoys there has been a casualty. There is a cost associated in bringing in that energy in both blood and treasure.

"So to drive up efficiency and to use alternative fuels, wind, solar, makes eminent sense to the military,” he said, noting that the use of solar blankets in Afghanistan meant fewer fuel resupply missions. “The principles of delivering your outputs more effectively, reducing your risks and reducing your costs reads across far more widely than just the military: most businesses would be looking for that too.”

Morisetti’s former employer, the Ministry of Defence, agrees that the climate threat is a serious one. The last edition of the Global Strategic Trends analysis published by the MoD’s Development, Concepts and Doctrine Centre concludes: “Climate change will amplify existing social, political and resource stresses, shifting the tipping point at which conflict ignites … Out to 2040, there are few convincing reasons to suggest that the world will become more peaceful.”

Schellnhuber was also clear about the consequences of failing to curb global warming. “The last 11,000 years – the Holocene – was characterised by the extreme stability of global climate. It is the only period when human civilisation could have developed at all,” he said. “But I don’t think a global, interconnected world can be managed in peace if climate change means we are leaving the Holocene. Let’s pray we will have a Lincoln or a Gorbachev to lead us.”