Detection of human influence on twentieth-century precipitation trends
Scientists found that currently observed rainfall patterns could not be accounted for by natural variation in precipitation — those caused by natural changes in climate, or volcanic eruptions and changes in solar radiation, which can also cause changes in rainfall. The model that did match the observed changes was the one that included response to human activities, such as increases in greenhouse gas emissions and sulphate and carbon aerosols — released as a waste-product of burning coal. "The thing that provides the best explanation, and explains most of the changes, is the human influence on the climate system," said one of the researchers. Many developing countries have experienced rainfall changes. Between the equator and 30 degrees north — including the northern part of sub-Saharan Africa and Latin America, South Asia, South-East Asia, and southern China — there has been an average 6–7 per cent decrease in rainfall over the last 75 years. Countries in the band between the equator and 30 degrees south — including the central part of sub-Saharan Africa and Latin America — have experienced an increase in rainfall because a band of heavy precipitation, called the intertropical convergence zone, has shifted further south (Source: SciDevNet 7 August 2007).
