Changes in Hydrological Cycle
Increase in global average temperature has caused increased evaporation rates, which has resulted in increased moisture availability for precipitation. Increased water vapour in the troposphere has led to increased warming as water vapour absorbs radiation.
- At the global level, large-scale variation has been observed in the trends in precipitation over the last 100-plus years, from 1900 to 2005. While an increase in the precipitation has been observed in the eastern parts of North and South America, northern Europe, and northern and central Asia, a decrease has been observed in the Sahel, the Mediterranean, southern Africa, and parts of southern Asia.
- Changes in precipitation and evaporation over the oceans are suggested by freshening of mid- and high-latitude waters (implying more precipitation), along with increased salinity in low-latitude waters (implying less precipitation and/or more evaporation).
- There has been an increase in the number of heavy precipitation events over many areas during the past century, as well as an increase since the 1970s in the prevalence of droughtsâ€”especially in the tropics and subtropics.