Q: What happens when you put 270 physics, chemistry and environment PhDs in a room for eight years?

A: You get a revolutionary manifesto for changing the planet and saving humankind. Its arguments so irresistible, that 195 governments around the world have no alternative but to assent to its publication in their joint names.

In the last eight months, the world's climate scientists have published three times under the banner of the IPCC. Their first two reports set out a stark message about how bad the climate crisis is now. In essence they told us that humankind has to adapt or die.

The third report, published on Monday, is a classic Hollywood narrative moment. It is where the doomsayer who has just told the cast why their plight is hopeless, then turns around and says: "This is going to sound crazy, but hear me out because it might just work".

The IPCC scientists’ plan is nothing less than a complete restructuring of the global economy, a re-ordering of the way we do business, a re-imagining of our cities and a re-purposing of what we do with our saved wealth.

On its own it would be written off as crazy and outlandish. But the evidence presented in the first two reports makes the case for this being our last best hope. And the authors by definition are all very serious people, not given to fanciful flights of enviro-populism.

Since the Industrial Revolution, our economies and all the wealth they generate have been based on carbon. Burning coal, oil, wood, peat and gas. This report says that to all intents and purposes, that entire economic model cannot go on any longer, and we have to replace carbon based energy with renewables, hydrogen and nuclear.

This is where the scriptwriters usually give the pessimist in the group a line like: "That’s ridiculous, you have no idea what you’re asking us to do".

But the argument for running with the IPCC plan is irresistible. If we want to keep temperature rise at or below 1.5 degrees, then in the next 30 years, we would have to reduce our coal consumption by 95%, our oil by 60% and gas by 45%.

If our heroes were less ambitious and prepared to settle for keeping warming to 2 degrees (a pretty awful world in which to live) they do not get off the hook. They would still have to cut coal consumption by 85%.

But that will not be enough. Industrial activity will have to be substantially relocated so that it happens near places where there is abundant renewable energy, not near ports, or the source of the raw material as we do now.

All of our built environments are going to have to change radically to allow people to live near their work, they say. Cities are going to have to effectively become non-motorised, as cars – yes, even EVs - make way for walking and cycling.

Future building cannot rely so heavily on concrete and steel. Everything we eat and wear will have to have a low environmental impact. There is no area they do not look to find a few more million tons of carbon dioxide fallen down the back of the couch.

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The say the world’s wealth has to be mobilised to achieve this – the pension and the hedge funds, the saved wealth of the world needs to be spent on this effort. And they say there is enough liquid wealth in the world right now to do what needs to be done, but that the transfer of wealth to the global south needs to increase by a factor of three.

Not even Karl Marx proposed such a radical transfer of wealth.

The governments of 195 countries might not be proclaiming this manifesto from the rooftops, but neither have they blocked the publication of a radical and revolutionary overhaul of the way we do everything.

The political aspiration expressed in Paris in 2015 by the world’s leaders to keep warming as close to 1.5 degrees as possible has been spelled out by the world’s scientists. This document will - if read and widely circulated - become a yardstick of ambition for the rest of this critical decade.