 According to 2006 studies by the National Oceanic and Atmospheric Administration, "the strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth's climate is warmed by increasing levels of greenhouse gases in the atmosphere".A greater percentage (+13%) of tropical cyclones are expected to reach Category 4 and 5 strength with 2 °C warming.Studies published since 2008, by Kerry Emanuel from MIT, indicate that global warming is likely to increase the intensity but decrease the frequency of hurricane and cyclone activity.