Satellite tracking of worldwide storms for more than a decade show melting polar ice sheets and increased rainfall are sending more fresh water into the oceans at the same time areas that need rain are getting less, according to a first-of-its-kind study by scientists at UC Irvine.
“In general, more water is good,” said Jay Famiglietti, UCI Earth system science professor and principal investigator on the study. “But here’s the problem: Not everybody is getting more rainfall, and those who are may not need it.”
“What we’re seeing,” he added, “is exactly what the Intergovernmental Panel on Climate Change predicted — that precipitation is increasing in the tropics and the Arctic Circle, with heavier, more punishing storms. Meanwhile, hundreds of millions of people live in semiarid regions, and those are drying up.”
The NASA-funded study, which put together a 13-year record of water patterns and will be published this week in the Proceedings of the National Academy of Sciences, says greenhouse gases have fueled higher temperatures, triggering monsoons and hurricanes.
All told, 18 percent more water fed into the world’s oceans from rivers and melting polar ice sheets in 2006 than in 1994, with an average annual rise of 1.5 percent, according to the study.
“That might not sound like much — 1.5 percent a year — but after a few decades, it’s huge,” said Famiglietti.
The study is continuing. It uses NASA and other world-scale satellite observations, rather than computer models, to track total water volume each month flowing from the continents into the oceans.
Researchers noted that “natural ups and downs” occur in climate data, and the ongoing study will look at long-term trends.