The chancellor, Philip Hammond, has written to the prime minister to warn against adopting the strict targets on greenhouse gas emissions recommended by the government’s advisers.

His intervention, first reported by the Financial Times (£), raises the important question of whether or not it makes economic sense to save the planet.

If the question sounds absurd, that’s because it is. If we fail to move to a low-carbon economy, the consequences will be dire. According to the Intergovernmental Panel on Climate Change, the body of the world’s leading climate scientists convened by the UN, we must drastically reduce our emissions in the next decade to avoid a catastrophic situation in which droughts, floods, heatwaves and extreme weather across the globe devastate lives, destroy agriculture, lay waste to wildlife and force millions to flee.

Set against that, the costs – of £50bn a year in investment, according to the Committee on Climate Change (CCC), which set out the case last month for a target of net-zero emissions by 2050, or £70bn a year, according to the Department for Business, Energy and Industrial Strategy – of maintaining our current lifestyles and orderly existences are trivial. The UK’s economy is worth roughly £2tn a year at present, so Hammond’s estimate of a £1tn cumulative cost by 2050 amounts to less than half of one year’s GDP in three decades.

Doug Parr, the chief scientist for Greenpeace UK, said: “The Treasury is putting their ideology before our wellbeing, and trying to shape the public debate for political ends. If you want to know whether a policy is good, include the benefits as well as the costs. In this case, the benefits include an economy fit for the 21st century, cleaner air, warmer homes, and maximising the chances of civilisation surviving. If reality doesn’t fit with the Treasury models, it’s the models that need to change.”

Yet the question – can we afford to keep our planet liveable? – has dogged debates on climate change for more than three decades. While scientists have issued ever stronger warnings about the likely impacts of climate change, nations have held back on taking action to reduce greenhouse gases, which have remained stubbornly high, though their growth rate has slowed.

The Stern review, conducted by the former World Bank economist Lord Stern for the Treasury in 2006, was supposed to settle this question once for all. Stern found, and his analysis has been widely backed up since, that the cost of dealing with climate change would be the equivalent of shaving 1-2% from GDP growth rates per year, compared with a cost of at least 5% of GDP per year from leaving global heating unchecked.

The CCC, in its recommendation of a net zero target, also estimated a cost of 1-2% of GDP by 2050, which is far outweighed by the costs of not acting. Nor would the UK be alone: the EU is considering a similar net zero target by 2050, while Norway, New Zealand and a few other countries have already done so.

Stern said that in the decade since his landmark review, the case for urgent action on the climate had grown even stronger. “In 2006, we understated the case: it has turned out that the risks of climate change were even greater than we knew, and the costs [of taking action] are far lower,” he said. “I think the current cost estimates will turn out to be far too high too, as we will adopt new ways of doing things.”

He added: “If reports of the letter are correct, Hammond has not understood the urgency of the challenge and the immense costs of climate change, and has failed to understand the capabilities of the UK. The UK is in an enormously powerful position to take leadership, with its strengths in research and development, in innovation, in finance in the City, with our skills in city planning – there is enormous potential here.”

The chancellor’s intervention may cause international consequences for the UK beyond Theresa May’s “legacy”. This weekend, the UN is set to discuss whether the UK or Italy should hold the COP26 conference in 2020, a crucial follow-up meeting to the 2015 Paris agreement. Awarding the conference to London now looks a harder decision.

When we ask whether we can afford to tackle climate change, we are really asking – as the IPCC report and decades of climate science show us – whether we want humanity to survive in anything like our current structures. If our economic system stands in the way of doing so, perhaps it is the economics that are at fault. And economics, like politics, are just a human construct. The physics of the earth’s atmosphere are not.

• Fiona Harvey is an environment correspondent for the Guardian.