Summary
Simpson et al. (2023) report a critical gap between climate model projections and observed hydroclimate trends in arid and semi-arid regions globally. Whilst all climate models simulate increased atmospheric water vapour capacity over these regions in response to warming, observational data show no corresponding increase, suggesting that moisture availability constraints in reality are more severe than model parameterisations represent. This discrepancy has potentially serious implications for the reliability of future projections of droughts, fire hazard, and water security in vulnerable arid and semi-arid agricultural systems.
UK applicability
The United Kingdom's predominantly temperate climate means direct applicability is limited; however, UK agricultural and water policy depends on climate projections for global regions that supply food imports and affect commodity prices. The identified modelling gaps may undermine confidence in projections for critical agricultural zones (Mediterranean, Middle East, sub-Saharan Africa) upon which UK food security partly depends.
Key measures
Atmospheric water vapour trends over arid/semi-arid regions; comparison of observed versus modelled hydroclimate data over four decades
Outcomes reported
The study compared observed atmospheric water vapour trends over arid and semi-arid regions during the past four decades against projections from climate model simulations. It identified a significant discrepancy: models predict increased atmospheric water vapour in these regions, whilst observations show no such increase.
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