Climate commitment in an uncertain world
Article first published online: 15 JAN 2011
Copyright 2011 by the American Geophysical Union.
Geophysical Research Letters
Volume 38, Issue 1, January 2011
How to Cite
2011), Climate commitment in an uncertain world, Geophys. Res. Lett., 38, L01707, doi:10.1029/2010GL045850., and (
- Issue published online: 15 JAN 2011
- Article first published online: 15 JAN 2011
- Manuscript Accepted: 2 DEC 2010
- Manuscript Revised: 28 NOV 2010
- Manuscript Received: 18 OCT 2010
- climate commitment;
- committed warming
 Climate commitment—the warming that would still occur given no further human influence—is a fundamental metric for both science and policy. It informs us of the minimum climate change we face and, moreover, depends only on our knowledge of the natural climate system. Studies of the climate commitment due to CO2 find that global temperature would remain near current levels, or even decrease slightly, in the millennium following the cessation of emissions. However, this result overlooks the important role of the non-CO2 greenhouse gases and aerosols. This paper shows that global energetics require an immediate and significant warming following the cessation of emissions as aerosols are quickly washed from the atmosphere, and the large uncertainty in current aerosol radiative forcing implies a large uncertainty in the climate commitment. Fundamental constraints preclude Earth returning to pre-industrial temperatures for the indefinite future. These same constraints mean that observations are currently unable to eliminate the possibility that we are already beyond the point where the ultimate warming will exceed dangerous levels. Models produce a narrower range of climate commitment, but undersample observed forcing constraints.