Source: Geophysical Research Letters
As the Earth’s climate warms due to increasing greenhouse gases, relative humidity (RH) over land is projected to decrease. Previously, the ocean has been considered the cause of the land RH decrease through its constraint on the changes of land surface energy and humidity. However, Zhou et al.  suggest that the decrease of land RH can take place independent of ocean influence.
Based on the CMIP6 models and the interactive-vs-prescribed soil moisture experiments of a coupled land-atmosphere model and its idealized radiative-convective equilibrium mode, this study shows that interactive soil moisture is necessary and sufficient to produce a decrease of land RH. Specifically, when soil moisture is prescribed to prevent it from responding to climate change, climate models fail to produce a decrease of land RH. In the radiative-convective equilibrium mode without ocean, soil moisture decreases under warming and land RH decreases consequently.
This study identifies the important role of land surface processes in controlling the RH response to warming and underscores the need for further research to understand the mechanistic pathways for how soil moisture adjusts to changes in surface fluxes to reach a drier equilibrium state.
Citation: Zhou, W., Leung, L. R., & Lu, J. (2023). The role of interactive soil moisture in land drying under anthropogenic warming. Geophysical Research Letters, 50, e2023GL105308. https://doi.org/10.1029/2023GL105308
— Guiling Wang, Editor, Geophysical Research Letters