How hot is too hot for our planet? For years, says Emma Marris in The Atlantic, the consensus has been clear: “no more than 1.5 degrees Celsius above pre-industrial levels”. That was the figure used in the 2016 Paris Agreement, and the political classes continually emphasise the importance of not exceeding it. Here’s the thing, though: that number “isn’t based on any scientific calculation”. It doesn’t mark some sort of “planetary threshold or ecological tipping point”. For decades, climate negotiators had talked about not exceeding two degrees. But in the late 2000s, a group of small island states – the likes of Fiji and Mauritius – argued that this would leave them under water, so they proposed 1.5 degrees. The number quickly “gained momentum” – and here we are.
Most climate scientists always knew this was an unrealistic target. But it’s been a hugely consequential one. In 2018, a UN-commissioned report concluded that staying below 1.5 degrees would require drastically slashing emissions by 2030 – which is where all the “we have x years to save the planet” rubbish comes from. And once we cross the threshold, probably within a decade or so, our collective failure will likely be used to justify the payment of reparations to poorer nations – it is already being cited in lawsuits brought by climate activists to force governments to curb emissions further. Of course everyone wants to curb global warming. But 1.5 degrees really is just a number. “A little better than 1.6 degrees, a little worse than 1.4 degrees.”