Two degrees is out of reach

This is the worrying news coming from the latest-generation of climate modelling efforts, just published in Geophysical Research Letters (abstract) by a Canadian team of scientists. The team use an Earth system model, fired up with a new generation of carbon emissions scenarios, to conclude that even limiting the 2100 temperature rise to 2.3C above pre-industrial would require “an immediate and rapid ramp down of emissions, followed by negative emissions (sequestration) in the later half of this century”.

As for the goal of holding “the increase in global average temperature below 2C above pre-industrial levels”, well, to get onto that trajectory we would have to take global emissions “down to zero immediately”, because the allowable cumulative carbon budget associated with that temperature target has already been emitted. Whoops! This is unfortunate because keeping below 2 degrees is now the world’s ‘official’ goal, which was agreed at Cancun amidst great celebrations (pdf here – see para 4). Now, in the cold light of day, it looks like we’re already too late.

Two degrees is out of reach

HT greendig via Twitter