"A changing climate will have real impacts on [the US] military and the way it executes its missions", US Defense Secretary Chuck Hagel said on Tuesday. And the US military is planning how to deal with the threat now.
The Department of Defense's 2014 Climate Adaptation Roadmap, published Tuesday, suggests climate change has the potential to exacerbate some of the world's most significant challenges, from disease to international conflict. It calls climate change a "threat multiplier" with the potential to increase the impact of numerous security concerns.
This isn't the first time the US military has expressed its concerns about climate change. But the roadmap is one of the first documents to "really go into great detail about what the US military should be doing in response to climate change now" Francesco Femia, co-director of the Center for Climate and Security thinktank, tells Carbon Brief. The report shows that military has decided the risk from climate change "is great and it's immediate", Femia says.
The roadmap outlines a number of new ways climate change could cause the military to be called into action. Its findings are driven by two things, Femia says: developments in climate science and "what the military is seeing on the ground".
The armed forces may have to respond to more natural disasters as a consequence of climate change both in the US and abroad, the report says - and the military should be prepared to be involved in responding to an increasing number of natural disasters at home.
Earlier this year, the government's National Climate Assessment highlighted how climate change could impact the US. The northeast can expect much heavier rainfall increasing the possibility of floods, while the southwest is likely to be increasingly hit by heatwaves, the assessment says. Extreme weather events are expected to become more intense and commonplace across the country.
It's a similar picture abroad. The US military is gearing up for more frequent operations requiring it to provide humanitarian assistance in response to floods, storms and drought.
But it's not just the military's humanitarian expertise that will be called on more often as a result of climate change. It's also anticipating more military operations to deal with international conflict.
The impacts of climate change can potentially impair access to food and water, damage infrastructure, and restrict availability to electricity, the report says. Such situations have the potential to "undermine already fragile governments" as well as heightening "tension between countries vying for limited resources", increasing the chance of violent conflict, it argues.
This broadly matches the conclusions of the Intergovernmental Panel on Climate Change's major report, released earlier this year. It said that while climate change may not cause conflict itself, it can amplify the drivers of conflict across the world.
One region in particular appears to have caught the US military's eye: the Arctic. Last year, the Department of Defense released its Arctic Strategy, outlining US military's vision for the rapidly-changing region.
It called for "responsible stewardship" of the delicate but resource-rich region, enforced by the US military.
Tuesday's report elaborates on the military's plans. "The opening of formerly frozen Arctic sea lanes will increase the need for the Department to monitor events, safeguard freedom of navigation, and ensure stability" in the Arctic, it says.
As well as having to deal with new conflicts, the military may be faced with new conditions that alter the way it conducts its missions.
The roadmap gives the examples of sea level rise making amphibious landings harder, and extreme weather causing air surveillance and reconnaissance to become more difficult. Extreme heat and cold may also affect the reliability of some weapons.
Climate change might also affect how the safety of its bases. For instance, as rainfall increases, many bases are becoming more prone to flooding. The army's access to food and water could become more restricted in certain areas, as climate change drives more intense droughts and heatwaves.
To address such challenges, the military has undertaken a survey of its 7,000 facilities to assess how to make them more climate resilient, the report says.
President Obama last month told the UN that the once-distant threat of climate change has"moved firmly into the present". The climate adaptation roadmap suggests the US military agrees.
When faced with uncertainty, the military takes the available evidence and uses it to "prepare for a future with a wide spectrum of possible threats", Hagel says. And assessing the impacts of climate change is no different.
The climate adaptation roadmap uses the military's experience to address what it sees as an immediate threat from climate change, while planning for the challenges climate science suggests are yet to come.
Originally published by Carbon Brief. Reproduced with permission.