Climate Talk

Overshoot explained: what 'temporary breach' of 1.5C actually means

The GONOM post defines overshoot as warming rising above 1.5C for a period before, in theory, being brought back down. I want to go a bit deeper because 'in theory' is carrying a lot there.

To bring temperature back down after overshoot, the world needs net-negative emissions: removing more CO2 than we emit, for decades. That means large-scale carbon removal (forests, soil, direct air capture, bioenergy with capture) at sizes that don't exist today.

Also, some impacts during overshoot may not reverse when temperature comes back down. Sea level keeps rising for a long time after warming stops, and some ice loss or ecosystem damage could be permanent. So 'temporary' overshoot can still leave permanent marks.

That's why I think the IISD framing about keeping overshoot as low as possible is the most useful one. Size and length of the overshoot both matter.