It’s the heat and the humidity: The complementary roles of temperature
and specific humidity in recent changes to the energy content of the
near-surface atmosphere
Abstract
Global change is a change in the planetary energy balance. It is usually
expressed as a change in near-surface (2 m) air temperature (Ta), but
changes to Ta represent only part of the atmospheric energy balance,
which includes specific humidity (q) and more. We analyzed MERRA-2
reanalysis data and 15 Atmospheric Model Intercomparison Project (AMIP)
models over the 1980-2014 period. Some 41%, 37%, and 49% of the
near-surface atmosphere showed significant increases in ET, ESH, and E,
respectively. The average increase in ET (ESH) was 10.6 J kg−1 year−1
(11.5 J kg−1 year−1) but AMIP models estimated that ET (14.5 J kg−1
year−1) exceeded ESH (13.7 J kg−1 year−1). Global near-surface Ta would
have increased at more than twice the observed rate if energy was not
partitioned into latent heat. Results demonstrate the critical role that
q plays in recent changes to near-surface atmospheric energy.