Purdue Climate Change Research Center

A Sensitivity to History

December 21, 2012

A sensitivity to history

Matt Huber - Nature Geoscience 6,15–16 (2013) doi:10.1038/ngeo1695 Published online

Questions about the sensitivity of Earth's climate to greenhouse gas forcing challenge our understanding of climate change. Matthew Huber looks at what we can learn from past greenhouse periods.

Predicting the climatic responses to post-industrial greenhouse gas perturbations is one of climate science's grand ambitions. A key parameter in these predictions is climate sensitivity — that is, the equilibrium temperature response to the doubling of atmospheric CO2concentrations. For considerations of climate change in the coming century, climate sensitivity is often restricted to feedbacks that respond quickly, such as clouds and sea ice. Model-derived estimates for this parameter range widely, from 2.1 to 7.1 °C per CO2 doubling. Attempts to further constrain climate sensitivity typically rely on empirical calculations with historical observations of temperature and forcing; for example, CO2 change1. Further constraints can be derived by comparing palaeoclimate model predictions with data from ancient climates23. Indeed, a comparison of past greenhouse proxy data with model output may be the only validation of model climate sensitivity most of us are likely to see in our lifetimes.

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