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Find Your Science at GSA
27 January 2012
GSA Release No. 12-06
Christa Stratton
Director of Education, Communication, & Outreach

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GSA Today, February 2012

A human-induced hothouse climate?

Boulder, Colo., USA — Writing in the February issue of GSA TODAY, David L. Kidder and Thomas R. Worsley consider the question of whether human-induced planetary warming has the potential to force Earth's climate to change to a condition similar to those of the warmest periods of Earth's history — a climate state referred to as a "hothouse climate" — or if the present cooler than average climate state will moderate these climate change effects.

Hothouse climates during the Phanerozoic (i.e., the past 542 million years) were achieved or closely approached during more than a dozen geologically brief intervals when large igneous province (LIP) volcanic carbon dioxide emissions triggered a cascade of warming feedbacks that pushed greenhouse climates toward hothouses. These large and geologically brief pulses of greenhouse gasses are thought to be a useful analog to study the effects of modern increases in carbon dioxide and their effects on global climate. Oceanographic and atmospheric changes that were deleterious to life developed during these warming intervals, and mass extinction coincided with a number of these episodes.

Human forcing of the modern icehouse to a hothouse climate would be difficult to achieve for two reasons. First, carbon dioxide release from human burning of past and estimated available fossil fuels in coming centuries would fall more than 100 times short of the carbon dioxide emitted by the much larger LIPs associated with hothouse climates, such as the end-Permian Siberian Traps. Second, cooling feedbacks in icehouse climates like the present one appear to have worked against major carbon dioxide injections to the atmosphere more effectively than those operating in past greenhouse climates. Thanks to human efforts, however, carbon dioxide is being added to Earth's atmosphere faster than any other known interval in Earth's history, and the degree to which this rate will overwhelm normal icehouse cooling feedbacks is difficult to precisely determine. Although Kidder and Worsley conclude that a human-induced hothouse is unlikely, a greenhouse climate in which melting of considerable amounts of Earth's existing ice will raise sea level by tens of meters appears quite possible within a matter of centuries. Recent modeling results by other workers suggest that such conditions are likely to persist for thousands of years.

The February GSA TODAY science article is now online. Peer-reviewed GSA TODAY articles are open access. Please discuss articles of interest with the authors before publishing stories on their work, and please make reference to GSA TODAY in articles published. Contact Christa Stratton for additional information or assistance.

A human-induced hothouse climate?
David L. Kidder and Thomas R. Worsley, Dept. of Geological Sciences, Ohio University, Athens, Ohio 45701, USA; doi:10.1130/G131A.1,