Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum
- Andreas Schmittner1,*,
- Nathan M. Urban2,
- Jeremy D. Shakun3,
- Natalie M. Mahowald4,
- Peter U. Clark5,
- Patrick J. Bartlein6,
- Alan C. Mix1,
- Antoni Rosell-Melé7
- 1College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331–5503, USA.
- 2Woodrow Wilson School of Public and International Affairs, Princeton University, NJ 08544, USA.
- 3Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
- 4Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14850, USA.
- 5Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
- 6Department of Geography, University of Oregon, Eugene, OR 97403, USA.
- 7Institució Catalana de Recerca i Estudis Avançats and Institute of Environmental Science and Technology, Autonomous University of Barcelona, Bellaterra, Spain.
- ↵*To whom correspondence should be addressed. E-mail: aschmitt{at}coas.oregonstate.edu
Abstract
Assessing the impact of future anthropogenic carbon emissions is currently impeded by uncertainties in our knowledge of equilibrium climate sensitivity to atmospheric carbon dioxide doubling. Previous studies suggest 3 kelvin (K) as the best estimate, 2 to 4.5 K as the 66% probability range, and nonzero probabilities for much higher values, the latter implying a small chance of high-impact climate changes that would be difficult to avoid. Here, combining extensive sea and land surface temperature reconstructions from the Last Glacial Maximum with climate model simulations, we estimate a lower median (2.3 K) and reduced uncertainty (1.7 to 2.6 K as the 66% probability range, which can be widened using alternate assumptions or data subsets). Assuming that paleoclimatic constraints apply to the future, as predicted by our model, these results imply a lower probability of imminent extreme climatic change than previously thought.
- Received for publication 28 January 2011.
- Accepted for publication 20 October 2011.
