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With a programme that looks at the numbers in the news, in life, and in statistical models predicting climate catastrophe, I'm Tim Harford.

Whether we like it or not, global warming is happening. The global temperature

has already gone up and it's going to go up more because the atmosphere is already full of carbon

dioxide and other greenhouse gases and we're continuing to add to that stock. Quite how much

it will increase by is a very important question for all of us.

Until relatively recently, during much of the 2010s and into the 2020s,

many scientists claimed that if we just kept on with business as usual,

then by the end of the century, global temperatures would increase by nearly five degrees centigrade.

That, in case you're wondering, is a big number.

Since pre-industrial times so far, they're up by a bit over one degree.

This projection was based on something called RCP 8.5,

a statistical scenario used by scientists to model the

future of the climate. You can still find scientific papers published in 2025 that make the same

claim. However, there's a good case that RCP 8.5 should never have been used as a business-as-usual scenario. And in hindsight,

it doesn't look like an accurate vision of the future at all. So what's going on?

So I am Dr. Z. Kausfather. I'm a climate scientist and the climate research lead at Stripe,

which is a financial technology company. Back in 2020,

I published a piece of nature, the world's sort of foremost scientific journal, along with a

researcher in Norway named Glenn Peters. And in it, we essentially argued that the climate science

community had been making a mistake for the last decade. And that mistake is that they had been

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