A drier than expected future, supported by near-surface relative humidity observations

Area of Science:

• Climate Science
• Earth System Science
• Hydrology

Background:

• Global climate models exhibit high dependency on specific models for terrestrial water cycle projections.
• Accurate prediction of future climate conditions, including water availability, is crucial for global environmental management.

Purpose of the Study:

• To constrain 21st-century projections of continental near-surface relative humidity using observational data.
• To assess the impact of different observational constraints on climate model projections of drying trends.

Main Methods:

• Utilized quality-controlled, gridded observational data for temperature and humidity.
• Constrained climate model projections by integrating surface temperature and relative humidity observations.

Main Results:

• Projections of continental drying are poorly constrained using only surface temperature observations.
• Integrating both temperature and relative humidity observations reveals an inevitable continental drying trend, especially in northern midlatitudes.
• Anthropogenic aerosols masked long-term drying trends in northern midlatitudes until the late 1980s.

Conclusions:

• Mitigation policies should consider factors beyond global warming levels.
• Urgent need for robust adaptation strategies due to projected continental drying.
• Land surface processes may contribute to uncertainties in climate models.