03/15/2010
A Climate Feedback between Tropical Cyclones and Ocean Circulation
Summary
More frequent tropical cyclones in Earth’s geological past may have contributed to persistent El Niño-like conditions in the tropics according to a team of climate scientists led by Dr. Alexey Fedorov of Yale University. The findings, which appeared in the February 25 issue of the journal Nature, could have implications for the planet’s future as global temperatures continue to rise due to climate change. The team used a hierarchy of climate and hurricane models to study the frequency and distribution of tropical cyclones during the early Pliocene epoch (roughly 5 to 3 million years ago) when temperatures were up to four degrees Celsius warmer than today. This period in the geological past, with CO2 concentrations in the range 350-400ppm, is considered the best analog to modern greenhouse climate. The team discovered that there were twice as many tropical cyclones during this period, that they lasted two to three days longer on average than they do now, and that, unlike today, they occurred across the entire tropical Pacific Ocean. The authors show that positive feedback between tropical cyclones and upper-ocean circulation in the Pacific can increase the number of storms and lead to warm El Niño-like conditions in the tropics. El Nino-like conditions result in major changes in storms and other weather effects, along with a temporary spike in global temperature. Including this feedback in climate models can potentially alter our projections for future hurricane activity and climate change in the tropics in general. The study was funded by the Department of Energy Office of Science and the National Science Foundation.
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References
Fedorov, A.V., Brierley, C., and K. Emanuel, 2010: “Tropical cyclones and permanent El Niño in the early Pliocene epoch.” Nature 463, 1066-1070. DOI:10.1038/nature08831