With historical peak of the Atlantic hurricane season just weeks away, NOAA’s Climate Prediction Center is preparing its updated outlook for the remainder of the season to be released today at 11 AM.To-date, three named storms have formed in the Atlantic basin: Ana, Bill, and Claudette. The Atlantic hurricane season began June 1 and continues through November 30. Previously, NOAA’s Climate Prediction Center said the 2015 Atlantic hurricane season will likely be below-normal. Given this new study, I wonder how future outlooks might play out if they give up on the idea that a warmer world equals more hurricanes?
Key Points of this new study:
- 4K cooler climate experiment is conducted using a high resolution AGCM
- Number of TCs is significantly increased in the 4K cooler climate
- Tropical cyclone genesis can occur at SST well below 26˚C
Masato Sugi, Kohei Yoshida, Hiroyuki Murakami
Accepted manuscript online: 31 July 2015 DOI: 10.1002/2015GL064929
More tropical cyclones in a cooler climate?
Recent review papers reported that many high-resolution global climate models consistently projected a reduction of global tropical cyclone (TC) frequency in a future warmer climate, although the mechanism of the reduction is not yet fully understood. Here we present a result of 4K-cooler climate experiment. The global TC frequency significantly increases in the 4K-cooler climate compared to the present climate. This is consistent with a significant decrease in TC frequency in the 4K-warmer climate. For the mechanism of TC frequency reduction in a warmer climate, upward mass flux hypothesis and saturation deficit hypothesis have been proposed. The result of the 4K-cooler climate experiment is consistent with these two hypotheses. One very interesting point is that the experiment has clearly shown that TC genesis is possible at sea surface temperature (SST) well below 26°C which has been considered as the lowest SST limit for TC genesis.