Australia's military has warned of a possible influx of climate refugees and an increased potential for conflict because of the effects of climate change.

Key points: A briefing note warns there is no "overarching strategy" to address climate change risks

A briefing note warns there is no "overarching strategy" to address climate change risks The Indo-Pacific region is projected to experience prolonged droughts and increased flooding from rising sea-levels

The Indo-Pacific region is projected to experience prolonged droughts and increased flooding from rising sea-levels Defence admits that their operations could be impacted by ocean acidification and extreme weather

Internal Australian Defence Force (ADF) briefing notes from last year, obtained by the ABC under Freedom of Information, also predict the military may be forced to increase patrols in Australia's northern waters to deal with "sea-borne migration" sparked by rising sea levels in the Indo-Pacific.

One document warns that climate change could "exacerbate the potential for conflict" and contribute to "state fragility and the undermining of economic development in our immediate region".

Former Defence Force chief Chris Barrie said Australia would be seen as the "land of opportunity" for many people affected by climate change.

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"I once suggested to government we might be talking 100 million people," said Admiral Barrie, who is now a member of the Global Military Advisory Council on Climate Change.

"One-hundred million people when we're only 40 million people — you can get the enormity of this problem. Frankly, it would be beyond our resources."

The Defence Force admits in the documents it "does not currently have an overarching strategy or policy to specifically address the risks posed by climate change beyond the 2016 Defence White Paper".



Climate change 'may directly impact' Defence operations

The ADF has refused to release documents relating to the impact of sea level rises and flooding on defence training areas, telling the ABC that it is not in the national interest.

"Release of this information could reasonably be expected to cause damage to the ability of the Defence Force to remain an effective force as well as potentially providing an avenue through which foreign incursions could significantly impact our critical infrastructure," it said.

But one briefing note warns that the Indo-Pacific region is projected to experience challenges such as prolonged droughts and increased flooding from increased sea levels.

"Sea level rise, ocean acidification, increase in extreme temperatures and a forecast increase in intensity of bushfires and extreme weather events may directly impact Defence capabilities, personnel and equipment," it read.

The ADF has already identified climate change as a challenge to Australia's future security.

Its 2016 Defence White Paper predicted that Australia may be called on to conduct more humanitarian and disaster relief operations.

The internal notes obtained under freedom of information go further in warning about climate change risks.

"Further, an increase in illegal foreign fishing or sea-borne migration to Australia because of climate change effects may increase demands for Australian Defence Force patrols in Australia's north waters," the briefing note said.

Admiral Barrie said Australia was "wide open" for climate refugees, using Bangladesh as an example — its border with India is already being heavily patrolled by the Indian military.

"Bangladesh — a very populated country — runs out of fresh water and also has problems with sea level rise. Where will all the Bangladeshis go?" he said.

'Impacts are unavoidable'

The briefing documents include a report assessing the impact of sea level rises and flooding on "selected defence training areas and ranges".

The report, by global infrastructure consultancy Aecom, says the "warming of the climate system is unequivocal…atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years".

Ex-ADF chief Chris Barrie says Australia will be seen as the "land of opportunity" for many people affected by climate change. ( AAP: Alan Porritt )

It states that the warming of Australia's mean air temperature could "reach 0.6 degrees Celsius to 5.1C depending on the emission scenarios".

The report cites such impacts as increased flooding, coastal erosion, bushfires and heatwaves.

"Even with considerable reductions in global greenhouse gas emissions, the inertia of the global climatic system means that many of these impacts are unavoidable."

Last year defence chiefs told the Senate's Foreign Affairs, Defence and Trade committee that rising sea levels and coastal erosion could damage military bases "in the short to medium term".

The committee's report warned that "climate change may also eventually contribute to greater irregular migration pressure in vulnerable countries to Australia's north, potentially becoming a substantial security threat to Australia".

A United States Department of Defence report released this year warned that more than two-thirds of the US military's "operationally critical installations" were under threat by climate change, with flooding being the biggest single risk.

Admiral Barrie said Defence had been considering the threat to their bases.

"I know what Defence has been doing is looking at some of its bases and things from an infrastructure development perspective and saying given sea level rise, given potential vulnerabilities our bases might have, doesn't it make sense to start thinking about moving some of those around," he said.

"I guess that's the bit that's been redacted [in the FOI documents] because no decisions have been made.

"I mean you don't have to look far beyond a map of sea level rise to realise just how serious this problem is."