The climate crisis is much more severe than most people and politicians realise.Most information, education and media reporting around climate change (global heating) focuses on reducing our annual emissions to a target based on a ‘trajectory of progressive reduction’, and eventually ‘net’ zero annual emissions by 2050 or some other date.

But this ignores the reality that it is the concentration of greenhouse gases in the atmosphere and their contribution to radiative forcing in real time that actually drive global heating.

Also, it’s not just CO2 that matters. The IPCC found that real time heating in the decade from 2010 to 2019 from relatively short-lived but very climate-active methane contributed more than half as much heating as CO2, even though its atmospheric concentration was much lower. But CO2 remains in the atmosphere for a very long time: much of it will still be in the atmosphere for more than 100 years, as shown below.

This article highlights some key insights that should underpin climate policy.

Every tonne of emissions adds to global heating and the longer it is in the atmosphere the bigger its cumulative impact

When we refer to our annual emissions in reports on climate change, it sends an unstated message that this is the most important indicator of our performance – and if annual emissions are declining towards ‘net’ zero by 2050, that is sufficient action. It’s not. As I pointed out to some young students recently, much of the emissions we release today will still be heating the planet when........

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