RealClimate: Area-based global hydro-climatological indicators
The World Meteorological Organisation (WMO) Global Climate Observing System (GCOS) and Copernicus Climate Change Services (C3S) both provide sets of global climate statistics to summarise the state of Earth’s climate. They are indeed valuable indicators for the global or regional mean temperature, greenhouse gas concentrations, both ice volume and area, ocean heat, acidification, and the global sea level.
Still, I find it surprising that the set does not include any statistics on the global hydrological cycle, relevant to rainfall patterns and droughts. Two obvious global hydro-climatological indicators are the total mass of water falling on Earth’s surface each day P and the fraction of Earth’s surface area on which it falls Ap.
Global surface area can now be analysed with satellite observations and global reanalyses such as the ERA5 reanalysis. Apparently, Earth’s fractional surface area receiving daily precipitation, Ap, has shrunk over time while the total mass of water falling on Earth’s surface P has increased. Furthermore, our recent analysis…