Environmental author and activist Naomi Klein doesn’t fly much these days on principle, but she’s come to Australia for the first time in 14 years because now is a crucial moment for climate change.

The weird thing is that Klein and the prime minister, Tony Abbott, are in complete agreement on one fundamental thing: both believe that seriously tackling climate change is incompatible with capitalism as we know it.

Of course, Klein starts with that and goes on to argue that our economic system must be upended if we are to have any chance to save the planet from the worst impacts of climate change. Abbott makes clear that he will protect the way things are at almost any cost.

Yet their starting point is the same: you can have perpetual economic growth, with all that goes with it, or you can have an approach to climate change that treats it as the most serious issue the planet faces, but you can’t have both.

As the critical Paris climate summit in December looms – the last realistic chance for an international accord that could limit warming to 2C – it’s that tension that seems to lie at the heart of what we confront. It was Klein’s book, This Changes Everything, that pushed the discussion out into the open.

Not that it’s accepted by everyone. There are many people arguing that it is still possible to contain global warming without making systemic change to market capitalism. Yet even many of those agree that we’re running out of time.

Abbott, in rhetoric and deed, has not embraced the pro-market view of climate change. He mentions global warming grudgingly and rarely enthuses about the economic opportunities for a sun soaked Australia.

He appoints sceptics to key government positions. He has cut Australia’s renewable energy target, speaks of coal in reverential terms and has done much to discourage “visually awful” wind farms. Climate change is to Abbott just another political problem to be managed. Labor’s policies, he says with relish, would “hit our economy with massive and unmanageable costs, massive increases in power prices, massive increase in the hit on families’ cost of living”.

Klein understands people like Abbott. Global warming threatens what they hold most dear: free markets, limited government regulation and unending material progress. So it makes sense, as Klein said on the ABC’s Q&A this week, that the political right is often so resistant to climate change.

“The reason for that is that if the science is true, then their world view collapses,” she said.

It may be true that Klein was anti-capitalist before she became concerned with climate change, but her ideas have become central to this argument, the questions she raises impossible to ignore.

She helped advise the Vatican before Pope Francis’ extraordinary June encyclical, Laudato Si. It was imbued with ideas that Klein would recognise – that unending material progress had a disastrous and destructive side, especially for the poor. That what was needed was a radical transformation of how our politics and our economy work.

“The time has come to accept decreased growth in some parts of the world,” the Pope said. He drew links between climate change, poverty, corporate greed, materialism, vested interests and political inertia. It was a moral call to action, infused with an activist’s rage.

It is stirring all this, but the critique of Klein’s work is that there is little detail about would replace neo-liberal capitalism. Her strength is that she lays out the problem so well and lets nobody off the hook.

She is scathing about some environmental groups, accusing them of pretending that global warming can be solved by fiddling a bit here and a bit there. It is deceptive, she argues, to suggest a solution wouldn’t inconvenience the west by redistributing resources to poorer countries that contributed little to global warming.

Most of her points are indisputable: there has been a huge mismatch between the problem of climate change and the response by governments; endless international meetings have been full of hot air; pledges to reduce emissions have turned out to lead to big increases of emissions; faith in technological solutions is often naïve; and given our tardiness, there is now a need to reduce emissions drastically and quickly.

To hold the earth’s warming to 2C will still mean a rise in deadly heatwaves, extreme weather and life-threatening sea rises. But at the moment, scientists say we’re on track for a 4C rise by the end of the century, which would be catastrophic for life on earth.

Little of that is seriously disputed, yet Klein’s key thesis remains contentious. The most prominent to dismiss it is UK economist Nicholas Stern, who rejects the economic growth versus climate action dichotomy.

He’s really countering governments that are fearful of the economic cost of climate action, but his points apply to Klein, too. There is now “much greater understanding of how economic growth and climate responsibility can come together and, indeed, how their complementarity can help drive both forward,” he said recently.

In Australia, too, the government’s rhetoric about the potentially disastrous economic cost of climate action is at odds with several studies.

Even long-time environmentalists in Australia question Klein’s key contention. Erwin Jackson, a “principled pragmatist”, is deputy CEO of the Climate Institute and he hasn’t read Klein’s book.

“All the analysis that’s been done at a macro level presuming we get along with it is that you can have a strongly growing economy and reduce emissions at the same time,” he says.

“The key barrier is political will, it’s not capitalism,” he says.

Mark Wakeham is the CEO of Environment Victoria. He and 80 others spent a full day with Klein in Melbourne this week workshopping how to put her book’s ideas into practice.

The big lesson, he says, is that green groups need to work much more closely with other organisations, such as unions. Yet Wakeham, too, is more optimistic than Klein about the role of capital.

“Where I see a divergence [from Klein] is that I see we’ll need a civilised capital to actually solve the problem,” he says. “The scale of investment that we’re going to need in clean energy is going to require all levels of government and organised capital to provide the capital for a solution”.

Both Jackson and Wakeham agree with Klein that dealing with climate change will have to mean a stronger role for government regulation.

As for Klein, she and such figures as Desmond Tutu and the founder of 350.org, Bill McKibben, are calling for mass action ahead of the Paris conference. They see a “great historical shift” on the way, as momentous as the anti-slavery and anti-apartheid movements.

Only a public uprising will force governments to treat climate change as the crisis it is, she argues. With that kind of movement, everything else will be shaken up, too. Which is, of course, Tony Abbott’s worst nightmare.

Naomi Klein will speak at the Festival of Dangerous Ideas, Sydney on 5 September.