It’s not easy these days to be shocked about climate change. We’ve heard all the dire predictions; we know that global warming at its worst will make the planet uninhabitable; and know the recalcitrance of some countries and some companies to do what everyone know is the right thing.

But here’s a figure that’s truly shocking – 2%!

That’s the best guess today of the percentage of global GDP the world needs to spend each year on technologies and infrastructure to prevent cataclysmic climate change.

Just 2%! Not 50%! Not 25%! Not 10% - just 2% of annual global GDP to save the Earth and civilisation, and countless people and animals and plants, from extinction. For such a potential catastrophe, 2% of global GDP sounds like a comparative trifling to pay.

In this TED Countdown presentation hot-off the press (June 2022), Yuval Noah Harari, the bestselling author of Sapiens, says he and his team of researchers poured over the climate change literature to confirm the 2% expenditure consensus.

Of course, 2% of global GDP annually is a VERY BIG NUMBER. Global GDP is estimated at US$85 trillion, which means our climate transition spend needs to be about US$1.7 trillion each year.

To help us understand what US$1.7 trillion / 2% of global GDP looks like and how feasible it might be to spend that much every year, Yuval gives us some very useful comparisons.

It’s reasonable to begin with other crises – the US spent 36% of GDP during World War II and 3.5% in 2008 to bail out its banks. In the first nine months of 2020, governments worldwide spent 14% of total GDP on COVID -stimulus packages.

Maybe a more apposite comparison is the annual subsidy governments around the world give to the fossil-fuel industry – US$500 billion. That’s right, the total annual investment to stop climate change is about 30% of what governments are already paying the polluters right now.

Yuval also offers a more novel alternative – buy all the cleared rainforest in South America for about US$800 billion. Other options include reducing food waste (2.4% of global GDP over two years) or tax evasion on profits by corporates or oligarchs that’s kept in offshore havens (US$1.4 trillion).

Whatever the climate change details are agreed in November at COP 27 in Cairo, as Yuval says, we now have a new number to consider along with the ambition to restrict global warming to 1.5C° above pre-industrial temperatures – it’s 2%.