If you want to imagine the politics of the future, think about climate refugees.

This week the ABC published internal briefing notes from the Australian Defence Force warning about huge population flows spurred by environmental disasters, with the former defence force chief Chris Barrie telling the broadcaster he once estimated the number at 100 million people.

Already, catastrophic weather forces some 24 million from their homes each year. We can expect more of that: more sudden floods and storms and other disasters of the kind that send people seeking shelter.

But the slower, incremental effects will be worse.

Even leading Morrison government ministers recognise the consequences of sea level rises.

You’ll remember that, back in 2015, Peter Dutton failed to see a live mic when yukking it up with Morrison and Tony Abbott about the likely fate of Pacific Island nations.

“Time doesn’t mean anything,” Dutton joked, “when you’re about to have water lapping at your door.”

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Meanwhile, arid countries also face an existential threat, from desertification and permanent drought.

By 2050, the World Bank expects the displacement of perhaps 143 million people from sub-Saharan Africa, South Asia and Latin America.

Those are, of course, some of the poorest regions in the world, places that benefited least from the Great Acceleration of consumer capitalism in the post-war era. The carbon-belching industries of the 21st century have not enriched the average person in Somalia – and yet the UNHRC now warns of climate change in that nation exacerbating the floods and droughts already sending millions into camps.

“The oft noted scandal of climate change,” say Geoff Mann and Joel Wainwright in their book Climate Leviathan, “is that whose who caused it will not live to see its full consequences and those who are suffering or will suffer worst did not cause the problem.”

Crucially, the Refugee Convention offers no succour at all to those displaced by climate.

It defines a refugee as “any person who owing to a well-founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group or political opinion, is outside the country of his/her nationality and is unable, or owing to such fear, is unwilling to avail himself/herself of the protection of that country”.

Climate refugees, in other words, don’t exist – at least, not from the perspective of the current legal apparatus.

They might have done nothing wrong (few people have smaller carbon footprints than the inhabitants of sub-Saharan Africa).

They might be the victims of processes set in train by others.

But that doesn’t matter.

As international law now stands, they’re not entitled to anything.

The urban theorist Mike Davis suggests that:

“Instead of galvanising heroic innovation and international co-operation, growing environmental and socio-economic turbulence may simply drive elite publics into more frenzied attempts to wall themselves off from the rest of humanity. Global mitigation … would be tacitly abandoned – as, to some extent, it already has been – in favour of accelerated investment in selection adaption for Earth’s first-class passengers. The goal would be the creation of green and gated oases of permanent affluence on an otherwise stricken planet.”

Australian refugee policy provides a pretty good inkling of what that might look like, with one of the richest countries in the world obsessively preoccupied with excluding desperate people seeking assistance.

Note that authorities classify the vast proportion of those detained in Australia’s offshore facilities as “refugees”. They’ve passed all the assessments; they’ve jumped through all the hoops – they’re legally entitled to protection.

Yet, according to the Refugee Council of Australia, the government spends more than $573, 000 on each of them, not to provide them with a new home but to keep them incarcerated.

Indeed, a 2016 report by Unicef Australia and Save the Children put the total cost of boat turnbacks, offshore and onshore detention between 2013 and 2016 at a staggering $9.6bn.

That’s the budget allocated to repel asylum seekers – even though, as a signatory to the 1951 Refugee Convention, Australia is obliged to protect displaced people from refoulement.

You can draw your own conclusions as to the likely treatment of those to whom Australia has no legal obligations at all.

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In the documents obtained by the ABC, the defence force says 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”.

That might be true in the narrowest sense. Yet the anti-refugee infrastructure created over the last decades creates – merely by its existence – a default policy on climate. Unless there’s massive political change, the bipartisan commitment to excluding people fleeing the carnage created (at least in part) by western military adventures will provide the basis for excluding people fleeing the carnage created (at least in part) by western industrial pollution.

As the novelist William Gibson once said, the future is already here – it’s just unevenly distributed.

If we don’t do anything now, the response to climate change will exacerbate and extend existing inequities, with the burden heaped upon the poor and the weak.

But the reverse also holds true.

If we want to prevent the population flows spurred by climate culminating in dystopia of barbed wire and armed enforcers, we need to fight the Orwellian system already enforced on Manus Island and Nauru.

Whatever justice we offer refugees today helps lay the foundation for justice in the much more challenging period to come.