By Sid Perkins
SAN FRANCISCO — Inhabitants of the tropics can expect to see more severe storms if sea-surface temperatures in the region continue to rise as Earth’s climate changes.
The growth of “thunderheads” — the massive and extremely tall clouds that generate the most severe thunderstorms — is driven by the rise of warm, moist air. A NASA satellite designed to monitor such deep convective clouds detects about 6,000 of them each day, says George Aumann, a climate scientist at the Jet Propulsion Laboratory in Pasadena, Calif. He and JPL colleague Joao Teixeira have analyzed five years’ worth of data from the satellite. They reported December 19 in San Francisco at the annual meeting of the American Geophysical Union that such rainfall-producing clouds are more frequent over areas where ocean temperatures are warm — a finding that bolsters a previous study that showed an increase in global rainfall as climate has warmed in recent decades.
For every 1 degree Celsius increase in average sea-surface temperature, the team noted a 45 percent increase in how frequently deep convective clouds appeared. Other studies show that Earth’s average temperature is now rising about 0.13 degrees Celsius per decade, says Aumann. So, if that temperature rise continues, the tropics will see the frequency of strong storms rise about 6 percent each decade.
At present, deep convective clouds cover only 1 percent or so of the world’s tropical oceans. Despite covering a small area, those storms are intense: They account for more than 25 percent of the rain falling on tropical oceans, Aumann notes.
