Paris (AFP) – The concept of a carbon budget is dead simple: figure out how much CO2 humanity can pump into the atmosphere without pushing Earth’s surface temperature beyond a dangerous threshold.

The 2015 Paris climate treaty enjoins the world to set that bar at “well below” two degrees Celsius (3.6 Fahrenheit) in order to avoid an upsurge in killer heatwaves, droughts and superstorms made more destructive by rising seas.

Last year, the UN’s climate science body concluded this…