It's the Heat and the Humidity: The Complementary Roles of Temperature and Specific Humidity to Recent Changes in the Energy Content of the Near-Surface Atmosphere

Global climate change is a change in the planetary energy (E) balance. It is usually expressed as a change in near-surface air temperature (T-a), but changes in energy content due to T-a (E-T) represent only part of the near-surface energy balance, which also includes E changes due to specific humidity (E-SH). We analyzed MERRA-2 and ERA5 reanalysis data and 15 CMIP6 Atmospheric Model Intercomparison Project (AMIP) models from 1980 to 2014. Some 44%, 39%, and 50% of MERRA-2 pixels showed significant increases in E-T, E-SH, and E, respectively. The average increase in E-T (E-SH) was 16.9 (13.6) J kg(-1) year(-1), but AMIP models estimated larger average E-T (21.6 J kg(-1) year(-1)) and E-SH (16.7 J kg(-1) year(-1)). Global T-a would have increased at nearly double the observed rate if energy was not partitioned into latent heat. Results demonstrate the critical role that specific humidity plays in recent climate changes.

Automated summary

Global climate change refers to a change in the planetary energy balance, in which specific humidity plays a critical role. The study found that from 1980 to 2014, the change in global near-surface air temperature (T-a) is influenced not only by the energy change due to T-a (E-T), but also by the energy change due to specific humidity (E-SH).