Meteorological data from the past 60 years suggested that tropical Atlantic trade winds have grown stronger. Until, that is, researchers Hiroki Tokinaga and Shang-Ping Xie corrected for a quirk in the observations.
Ships that traverse the Atlantic are the primary source of historical wind data. As ships have gotten taller, their anemometers measure wind at correspondingly higher altitudes.
Recalculating the data to adjust for those changes and factoring in observations from other sources, the International Pacific Research Center scientists found that trade winds over the Atlantic have weakened significantly.
At the same time, the pattern of ocean surface temperatures has changed, resulting in significantly more rain to the equatorial Amazon and Guinea coast and less rain in the Sahel region of Africa, they report Feb. 6, 2011, in Nature Geoscience online.
In addition, upwelling of cold, nutrient-rich water that supports marine life has declined in the eastern tropical Atlantic, they write.