51�Թ�

Unstable at normal sea-level pressure and temperatures, gas hydrates can be dangerously explosive as temperatures rise.

An observer in Antigua reported a sea-level pressure reading of 27.2 inches.

Low sea-level pressure and favorable wind conditions also helped.

A phenomenon called the El Nino-Southern Oscillation has precipitated widespread changes in sea-level pressure across Indonesia, Australasia and the tropical Pacific.

But the first quarter was 15 percent warmer than usual as the jet stream shifted north and changed the North Atlantic Oscillation, which measures surface sea-level pressure differences, from negative to positive.