What is it about?

Persistent dry spells represent a growing matter of concerns in many regions worldwide. Yet, global projections of seasonal precipitation are much less reliable than their temperature counterparts. Here, future changes in meteorological drought properties are characterized through the multi-scale standardized precipitation index. Two extended seasons are distinguished from October to March and April to September, respectively. Consistent and statistically significant large‐scale patterns of changes in mean frequency, duration, intensity and severity date are projected across timescales and seasons, leading to the definition of regional “dry spots” such as northern South America and the Caribbean Islands. Yet, the magnitude and sign of such changes remain model‐dependent over a majority of regions and such modeling uncertainties cannot be simply related to contrasted model responses in global mean temperature or regional precipitation over the historical period.

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Why is it important?

Droughts refer to periods of time with substantially below-average moisture conditions, usually covering large areas, during which limitations in water availability result in negative impacts for various components of natural systems and economic sectors. Depending on the variables used to characterize it and the systems or sectors being impacted, drought may be classified in different types such as meteorological (precipitation deficits), agricultural (e.g., crop yield reductions or failure, often related to soil moisture deficits), ecological (related to plant water stress that causes e.g., tree mortality), or hydrological droughts (e.g., water shortage in streams or storages such as reservoirs, lakes, lagoons, and groundwater). Meteorological droughts generally precede the other types but are unfortunately the most model-dependent in global climate projections. Better understanding the geographical distribution of their projected changes and better quantifying the associated modelling uncertainty thus represent a priority for the design of no-regret adaptation policies.

Perspectives

The present study provides a comprehensive evaluation of the CMIP6 model ability to simulate the local properties of multi‐scale meteorological drought events. It also analyzes how these properties may change under two illustrative emission scenarios and how this response may vary across regions and models. “Dry spots” have been identified based on their much stronger severity in a future climate, regardless of the season and timescale. An attempt has been also made to narrow the inter‐model spread in the projections, with limited success so far given the weak connection with climate sensitivity, the strong internal variability of seasonal precipitation and, though to a lesser extent, persistent uncertainties in the observations. Further studies could pay more attention to precipitation data homogenization, changes in drought seasonality, but also to annual and longer timescales given their potentially greater impacts on both societies and natural ecosystems. So far, the results suggest that many regions that are already vulnerable to natural precipitation variability will soon face an even more difficult situation unless drastic mitigation policies are rapidly implemented. Regardless of the mitigation efforts and of the new advances expected by the Earth system modeling community, the next generation of climate projections will be increasingly constrained by the emergence of regional climate change in the observations. In the meantime, it could be wise for decision‐makers to consider the inter‐model spread as an additional motivation to act rather than as a pretext for inaction.

Hervé Douville

Read the Original

This page is a summary of: How Do Projections of Meteorological Droughts Vary Across Models and Regions?, Geophysical Research Letters, February 2026, American Geophysical Union (AGU),
DOI: 10.1029/2025gl119644.
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