Environment Counts | Greenhouse gases amplify the effects of changes in the Earth’s climate
Author: Geoff Zeiss – Published At: 2012-12-09 01:57 – (1404 Reads)
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This article assumes that the ultimate driver of glacial-interglacial transitions has been the weak influence of varying insolation (solar radiation) associated with Milankovitch cycles (changes in the Earth’s orbital geometry). The Vostok ice cores from Antactica have shown a close, positive correlation between temperature and CO2 and CH4 concentrations in the Earth’s atmosphere over the past 400,000 years. This article makes the argument that CO2 and CH4 concentrations amplify the weak influence of changes in the Earth’s orbit and are responsible for much of the observed paleoclimatic variation during the past million years. Physics Today, October 2012, p16.
 GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L10703, 2006
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reviewed here, it is assumed that the timing of glacial-interglacial cycles is triggered by cycles in the amount of sunlight reaching the earth. But the variation in the amount sunlight reaching the Earth is so weak that the observed magnitude of warming and cooling, during glacials and interglacials, cannot be explained by the solar variations alone.
The Vostok ice core record shows that over about 400,000 years there is a close, positive correlation between temperature and atmospheric carbon dioxide and methane. This article argues that the observed temperature change leading to glacials and interglacials is explained by the strong variation in atmospheric carbon dioxide and methane concentrations.
The article suggests that there is a positive feedback in the earth climate system : a small initial warming caused by a change in solar input causes carbon dioxide and methane concentrations to rise, which in turn causes more warming. The feedback works in the opposite way leading to cooling when solar-input decreases.
Applied to our current climate, it is suggested that the feedback mechanism amplifies the warming caused by anthropogenic GHG emissions. It is estimated that if doubling CO2 concentrations would cause 1.5–4.5°C warming, the feedback mechanism would actually result in 1.6–6.0°C warming or up to 1.5°C warmer temperatures than currently predicted by the IPCC.
Ice-driven CO2 feedback on ice volume, W. F. Ruddiman, Clim. Past, 2, 43–55, 2006
