A landmark assessment of climate change, released on Monday (Aug 9) as a consensus statement by 234 international scientists, makes clear that the world faces a frightening future even if the global economy is decarbonised rapidly.

Failure to cut greenhouse gas emissions deeply would lead within a few decades to what a leading climatologist called “hell on earth”.

The stark warnings of the Intergovernmental Panel on Climate Change will come as no surprise to those who have watched evidence of human-induced heating accumulate since the IPCC last reported in 2013. No one should imagine that this report is unduly alarmist.

It represents mainstream scientific opinion which some climatologists would express even more strongly.

Nor did the lengthy IPCC writing process allow the authors to take full account of the latest signs that climate may be changing even faster than most models had suggested: Extreme heatwaves, catastrophic floods and rapid melting of Arctic ice and permafrost.

The report makes depressing reading but provides policymakers with no excuse to throw up their hands and give up.

It shows actions by business and governments in the near future will have an impact for generations; some effects of climate change, such as rising sea levels and melting polar ice, will last for hundreds of years.

In the IPCC’s most optimistic but achievable scenario, “immediate, rapid and large-scale reductions” in emissions limit the rise in global temperatures to a peak of 1.6°C above pre-industrial temperatures shortly after 2050.

This would further increase the frequency and intensity of disruptive weather events, such as storms, droughts and heatwaves, but would ensure that earth remains essentially liveable.

Under a very high emissions scenario, warming could reach 3°C by 2060 and 5.7°C by 2100, threatening the very existence of human civilisation.

The report should fortify the resolve of global leaders to agree on a far-reaching route toward net zero emissions at November’s COP26 summit in Glasgow.

Many, including conference host Boris Johnson, will have to resist political pressure from people who remain sceptical about the severity of climate change in the face of all the evidence or who only see the short-term economic costs of decarbonisation.

Although advocates of strong action often emphasise the economic growth generated by investment and innovation on the path to net zero, they should not paint an unrealistically rosy picture.

Cutting carbon-intensive activities will bring real pain and costs too, requiring appropriate compensation.

The IPCC report also should prompt environmental campaigners to abandon some traditional prejudices, particularly against nuclear power.

Smaller nuclear plants deserve investment for the role they could play in generating carbon-free electricity. Attitudes may need rethinking, too, to geoengineering: Use of technology to cool the planet by removing CO2 from the atmosphere or reflecting more of the sun’s energy into space.

Besides concerns about safety and unintended consequences, campaigners fear that the prospect of a technological fix will reduce the incentive to tackle the fundamental problem — that we are emitting too much greenhouse gas.

But research into geoengineering would be a worthwhile precaution. With such a serious climate emergency looming, the world cannot afford to rule out anything that might be part of the solution.

But, as the IPCC recognises, the main route away from hell on earth must involve weaning humanity off its carbon addiction. FINANCIAL TIMES