Humans have released carbon dioxide and other greenhouse gases, and the result is an accumulation of heat in the Earth's climate system, commonly referred to as "global warming". "How fast is the Earth's warming?" is a key question for decision makers, scientists and general public.
Previously, the global mean surface temperature has been widely used as a key metric of global warming. However, a new study published in AGU's Eos proposed a better way of measuring global warming: monitoring ocean heat content change and sea level rise. The authors come from a variety of international communities including China (Institute of Atmospheric Physics, Chinese Academy of Sciences), U.S.A. (NCAR, NOAA, and University of St. Thomas) and France (Mercator Ocean).
To determine how fast the Earth is accumulating heat, scientists focus on the Earth's energy imbalance (EEI): the difference between incoming solar radiation and outgoing longwave (thermal) radiation. Increases in the EEI are directly attributable to human activities that increase carbon dioxide and other greenhouse gases in the atmosphere. Extra heat trapped by increasing greenhouse gases mainly ends up in the oceans (more than 90% is stored there). Hence, to measure global warming, we have to measure ocean warming!
Ocean heat content ...