Just imagine that the Australian Government approaches the New Zealand Government with an offer to pay this country $100 billion to take 1 million of its people and resettle them here.
Why? Because Australia has been savagely affected by climate change.
It can't provide enough water and food for its citizens. It is in the grip of extreme droughts, heatwaves and fires caused by climate change. Not to mention rising sea levels affecting coastal cities. The $100b would be paid over a 10-year period.
What would New Zealand do?
This question is unlikely to create a problem for Jacinda Ardern during her period as Prime Minister. Nor would it have been at the back of her mind as she "poked the bear" yet again at the Pacific Islands Forum this week, positioning New Zealand as a poster child in the international climate warrior stakes — against Australia.
Australian Prime Minister Scott Morrison later helped Ardern by characterising her comments ("stop digging and exporting coal" is how other Pacific leaders put it) as having been "misinterpreted".
But both prime ministers are looking in the wrong end of the telescope.
If the Pacific has an existential problem from prospective climate change, then so too does Australia.
The thought experiment I alluded to was posed to politics students at Otago University this year — and also put to a number of us who took part in a series of guest lectures on foreign policy.
We can assume that under current climate change scenarios, New Zealand will at some date be inundated with calls to accept "climate refugees" from the Pacific Islands. But notably, as editorialists across the Tasman have been pointing out, Australia is already far more virtuous than this country when it comes to accepting refugees on a per capita basis.
But some of those Pacific Islands are also dependencies of New Zealand and it would be hard to block them.
Who would we welcome first? Australians with their chequebook? Or Pacific Islanders?
If our thought experiment became reality, would our Government take account of the fact that Australia has for many years been an economic safety valve for this economy? That our greatest export to that country has probably been our talented people — hundreds of thousands of them in search of greater opportunity and higher wages?
And that a helping hand in return might not go amiss?
Or would our prospective future New Zealand Government turn out to be as much of a realist when the chips are down, as the current Australian Government is when it fires back New Zealand-born criminals after they have served their time?
The reality is that New Zealand is blessed with natural resources and can power up the country through hydro, geothermal and, increasingly, wind. And yes, we do export oil.
Just five years ago, former Australian Liberal Treasurer Joe Hockey was boasting that Australia was poised to be the world's largest exporter of energy within a decade, still quarrying massive loads of iron ore and sharing New Zealand's destiny of being an Asian "food basket".
Hockey's "future Australia" would have an enormous demand for immigrants to staff all those gas wells, coal and uranium mines, quarries and farms — not to mention all the professional jobs that go with a prosperous economy.
"We're blessed to be in the fastest growing time zone in the history of humanity," the Australian Treasurer chirped to the audience at an event I attended to take note of the "insatiable demand that was going to continue".
Australia was investigating using its uranium reserves for nuclear energy. But it also had about 400 years of coal it expected to underpin its economy into the future.
Attitudes are changing and it now has some hard economic decisions ahead of it.
But so does New Zealand.
It is obvious that this Government, like its predecessors, has cut the agricultural community considerable slack over its emissions — yet Pacific Island leaders this week were not being silkily nudged to slag off New Zealand.
The point of this is to say we don't know yet how the future will pan out.
But plenty of forecasting from the CSIRO and others points to some severe impacts ahead for Australia.
As to the thought experiment, it is difficult to work through, isn't it?
Where would we house 1 million Australians?
Would we build a new city with the $100b?
And would it be enough?
As we head into a third weekend in a row with foul weather warnings in some parts of the country, it's an interesting question to ponder.