VOL. 34, L19703, doi:10.1029/2007GL031018, 2007

Long term climate implications of 2050 emission reduction targets
Andrew J. Weaver, Kirsten Zickfeld, Alvaro Montenegro, and Michael Eby

Received 15 June 2007; revised 27 August 2007; accepted 7 September
2007; published 6 October 2007.

Abstract: A coupled atmosphere-ocean-carbon cycle model is used to
examine the long term climate implications of various 2050 greenhouse
gas emission reduction targets. All emission targets considered with
less than 60% global reduction by 2050 break the 2.0 threshold
warning this century, a number that some have argued represents an
upper bound on manageable climate warming. Even when emissions are
stabilized at 90% below present levels at 2050, this 2.0 threshold is
eventually broken. Our results suggest that if a 2.0  warming is to
be avoided, direct CO2 capture from the air, together with subsequent
sequestration, would eventually have to be introduced in addition to
sustained 90% global carbon emissions reductions by 2050.


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