Humanity, through its actions, or lack of action, has unequivocally overheated the planet. Nowhere on Earth is escaping rising temperatures, worse floods, hotter wildfires or more searing droughts.

The future looks worse. “If we do not halt our emissions soon, our future climate could well become some kind of hell on Earth,” says Prof Tim Palmer at the University of Oxford.

This would be the sentence for these climate crimes, but it has yet to be passed down. The world can avoid the harshest punishment, but only just. 

Immediate repentance for the delays that have brought the world to the brink is required in the form of immediate and deep emissions cuts.

The key aspect of the IPCC report is that the 42-page summary is agreed, line by line, by every government on the planet, with the scientists vetoing any politically convenient but unscientific proposal.

As a result, governments that continue to fail to take action have nowhere left to hide – the crystal-clear report has bust all of their alibis.

“Too many ‘net-zero’ climate plans have been used to greenwash pollution and business as usual,” says Teresa Anderson at ActionAid International.

The report exposes such plans with its stark statement that immediate action is the only way to avoid ever-worsening impacts, of which today’s wildfires in California, Greece and Turkey, floods in Germany, China and England, and heatwaves in Canada and Siberia are merely a foretaste. As Greta Thunberg says, the climate crisis must be treated as a crisis.

The action required is well known and the IPCC report must be the spur for it to be taken, says António Guterres, the UN secretary general: “This report must sound a death knell for coal and fossil fuels, before they destroy our planet. 

"If we combine forces now, we can avert climate catastrophe. But, as the report makes clear, there is no time for delay and no room for excuses.” 

Every choice made now matters. Helen Clarkson, the CEO of the Climate Group, which represents 220 regional governments and 300 multinational businesses, covering 1.75 billion people and 50% of the global economy, says: “Every decision, every investment, every target, needs to have the climate at its core.” 

The gravity of the situation laid out in the report blows away blustering over the supposed costs of climate action. In any case, not acting will cost far more. 

“It’s suicidal, and economically irrational to keep procrastinating,” says Prof Saleemul Huq, director of the International Centre for Climate Change and Development at the Independent University, Bangladesh.

For those governments and businesses that still chose inaction, the IPCC report may well end up being used as key evidence against them in real courtrooms. “We’ll be taking this report with us to the courts,” says Kaisa Kosonen at Greenpeace.

“By strengthening the scientific evidence between human emissions and extreme weather the IPCC has provided new, powerful means to hold the fossil fuel industry and governments directly responsible for the climate emergency,” she says. 

“One only needs to look at our recent court victory against Shell to realise how powerful IPCC science can be.” 

Hope remains, just. Christiana Figueres, who was UN climate chief when the Paris deal was sealed in 2015, says: “Everything we need to avoid the exponential impacts of climate change is doable. But it depends on solutions moving exponentially faster than impacts.” 

The IPCC’s report means all the evidence that will ever be needed is now in place. 

“The continued dithering to address climate change is no longer about the lack of scientific evidence, but directly tied to a lack of political will,” says Kristina Dahl of the Union of Concerned Scientists.

That means political leaders are now in the dock and the vital UN Cop26 summit in Glasgow in November may be the last hearing at which they can avoid the judgment of history.

• Guardian