Additional peril

Reliance on fossil fuels, she notes, invariably requires having to transport them. The more you have to transport fuels, the more costly the risks.

"It means putting ourselves at additional peril," she notes.

And the role of Middle East oil in determining the US geopolitical strategy is an obvious example of this.

Ms Goodman says challenges for the US military include the vulnerability of military assets themselves, such as naval bases that are at risk from rising sea levels and storm surges, as well as the fact strategic planning requires preparation for more global instability through crop failure or forced migration within and across borders, and spending more time and effort on disaster relief.

Sherri Goodman, a former deputy under secretary of defence for environmental security in the US, says Australia lies in "disaster alley". Wilson Centre

" The way it's been managed in the defence budget is that oil and gas is taken as an additional, huge cost on top of the normal spend," she says.

"They'd much rather that that money was available for equipment and personnel so that's become an incentive to innovate," she said.


Broader use of renewables

That can involve anything from solar-powered batteries for soldiers or micro grids at forward positions to broader use of renewables in defence establishments.

The US military has dedicated programs to try to deal with this growing strategic risk by investing in energy research, development and demonstration programs, and new technologies.

Ms Goodman says that, as in Australia, the climate change debate in the US is still "overly politicised, despite the science being abundantly clear".

However, she says climate deniers have shifted from denying climate change to arguing about how fast it is happening, thus introducing uncertainty into what to do about it.

But, she says, from the military's perspective, there is no opportunity to wait, likening it to being prepared for a threat of terrorism, weapons of mass destruction, or North Korea's nuclear capacity.

"You don't wait until you have 100 per cent certainty you are going to be attacked," she said.