27 July 2007
A paper published on 26 July in Nature breaks new ground in climate change research by showing for the first time that anthropogenic activities have influenced the changing global precipitation patterns over the last century. The international team of authors included CSD senior scientist Susan Solomon.
Background: Over the past century, climate records indicate sizable shifts in precipitation patterns around the globe, including increased rain and snowfall in northern regions, drier conditions in tropical areas north of the equator, and increased rainfall in the southern tropics. The authors looked at average conditions over broad regions of the globe and compared them to changes anticipated due to human influence on climate. They studied the combined effect of changes in greenhouse gas emissions as well as sulfate aerosol concentrations in the atmosphere. By using an analysis combining the results from 14 different models, the authors increased the accuracy of their results.
Significance: Human-induced changes have not previously been detected in global studies of precipitation, partly because drying in some regions cancels moistening on others, reducing the global signal. These authors used the patterns of the changes in different latitude bands instead of the global average. The paper shows that human-induced climate change has caused most of the observed increase in precipitation north of 50° latitude, a region that includes Canada, Russia, and Europe, as well as in the southern hemisphere. The anthropogenic influence is also contributing to the drying observed in a broad region north of the equator that includes Mexico, Central America, and northern Africa. These shifts may have already had significant effects on ecosystems, agriculture, and human health, especially in regions that are sensitive to changes in precipitation (e.g., the Sahel region in northern Africa). This work supports NOAA's Climate Goal to understand climate variability and change to enhance society's ability to plan and respond.