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Contrasting the Hydrological Cycle in Past and Future Warm Climates - with implications for Ocean Overturning Circulatio

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Date and time Mar 18, 2019
from 04:10 PM to 05:00 PM
Location MP606
Host Deepak Chandan

Natalie Burls

George Mason University (Washington D.C.)

Contrasting the Hydrological Cycle in Past and Future Warm Climates - with implications for Ocean Overturning Circulatio

 
During the warm Miocene and Pliocene epochs, subtropical regions had enough precipitation to support rich vegetation and fauna. Only with global cooling and the onset of glacial cycles some 3 million years ago, towards the end of the Pliocene, did the broad patterns of arid and semi-arid subtropical regions become fully developed. However, current projections of future global warming caused by CO2 rise generally suggest the intensification of dry conditions over these subtropical regions, rather than the return to a wetter state. What makes future projections different from these past warm climates? In an effort to answer this question, this talk focuses on the warm Pliocene – the most recent time in Earth’s history during which reconstructed atmospheric CO2 concentrations are estimated to have been in the region of 400ppm. We investigate this question by comparing a typical quadrupling-of-CO2 experiment with a simulation driven by sea surface temperatures closely resembling available reconstructions for the early Pliocene. Sensitivity studies exploring cloud controls on tropical climate, and theoretical arguments inferring Pliocene cloud radiative forcing will be discussed, as well as implications for the meridional ocean overturning circulation in the Pacific basin during the Pliocene.
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