The two scientists decided to unravel the paradox after Parlange, a professor in Hopkins' Department of Geography and Environmental Engineering , heard a Russian hydrology researcher refer to it during a symposium on water resources and global warming, held last spring at Hopkins. The Russian researcher had no clear explanation for some evaporation figures that did not seem to align with other climate change indicators. To probe the paradox, the researchers focused on the Earth's hydrologic cycle, in which water falls to the ground as rain or snow, soaks into the soil or moves into bodies of water, then evaporates to form clouds that start the cycle once again. Over the past two or three decades, data collected in parts of the United States, the former Soviet Union, India and Venezuela have indicated that the pace of this hydrologic cycle is picking up. In other words, it has been taking less time to complete each cycle of precipitation through evaporation.
Scientists disagree on the reason.
It may be a natural phenomenon or one that humans have triggered by releasing more carbon dioxide. But the existence of this accelerated water cycle is now widely accepted. Nevertheless, many climate researchers have been unable to explain why evaporation figures have decreased in areas where rainfall and cloudiness have become more prevalent. But it's been an awkward problem that has bothered scientists studying climate change. To explain the paradox, Parlange and Brutsaert looked at the way evaporation is recorded.