The energy source that drives the atmospheric and oceanic circulations is the solar radiation,
whose direct effect is to heat the atmosphere and the underlying surface, and therefore generates
the evaporation of water from the surface of land and oceans. The water vapor is transported by winds
and condensed to form clouds and precipitation that falls to land and oceans ultimately. The sequence
of above processes is called the hydrologic cycle (also known as water cycle). The hydrologic cycle is
an essential part of energy cycle in the climate system and plays a fundamental role in affecting Earth's
climate. Its role in El Niņo-Southern Oscillation (ENSO) is an example. ENSO is the strongest natural
interannual climate signal and has widespread effects on the surface climate (such as surface temperature
and precipitation) in different regions of the globe.
A central question in climate change is how the hydrological cycle responds to man-made greenhouse gases?
Does the hydrologic cycle play the same role in El Nino warming as in global warming?