If you are a bit incredulous about cosmic rays affecting climate then try Sahara dust storms affecting Atlantic hurricanes.

Writing today (Oct. 10, 2006) in the journal Geophysical Research Letters, the scientists discuss a surprising link between hurricane frequency in the Atlantic and thick clouds of dust that periodically rise from the Sahara Desert and blow off Africa's western coast. Lead author Amato Evan, a researcher at UW-Madison's Cooperative Institute for Meteorological Satellite Studies (CIMSS), pored over 25 years of satellite data - dating from 1981 to 2006 - and noticed the correlation. During periods of intense hurricane activity, he found, dust was relatively scarce in the atmosphere. In years when stronger dust storms rose up, on the other hand, fewer hurricanes swept through the Atlantic. . .

Evan decided to explore the correlations between dust and hurricane activity after CIMSS research scientist Christopher Velden and others suggested that dust storms moving over the tropical North Atlantic might be able to suppress the development of hurricanes.

The UW-Madison researchers say that makes sense because dry, dust-ridden layers of air probably helps to "dampen" brewing hurricanes, which need heat and moisture to fuel them. That effect, Velden adds, could also mean that dust storms have the potential to shift a hurricane's direction further to the west, which unfortunately means it would have a higher chance of hitting U.S. land.

While the UW-Madison work doesn't confirm that dust storms directly influence hurricanes, it does provide compelling evidence that the two phenomena are linked in some way. "What we don't know is whether the dust affects the hurricanes directly, or whether both [dust and hurricanes] are responding to the same large scale atmospheric changes around the tropical Atlantic," says Foley. "That's what future research needs to find out."

Correlation again, like earlier work on cosmic rays effects, needing more research to identify a mechanism that can cause the effects.