He et al. (2025) Drying Tropical America Under Global Warming: Mechanism and Emergent Constraint

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Geophysical Research Letters
• Year: 2025
• Date: 2025-12-18
• Authors: Chao He, Xiaolong Chen, Tianjun Zhou, Fred Kucharski, Fengfei Song
• DOI: 10.1029/2025gl117131

Research Groups

Not specified in the abstract.

Short Summary

This study investigates the mechanisms driving precipitation changes in Tropical America (TAM) using CMIP6 models, revealing that amplified equatorial Pacific warming induces a Gill-type atmospheric response that suppresses TAM rainfall. It finds that climate models likely underestimate future TAM drying, projecting a regional mean annual rainfall decline of 46 mm per 1 K of global warming, which is 1.5 times higher than raw projections.

Objective

• To understand the atmospheric mechanisms linking equatorial Pacific warming to precipitation changes in Tropical America (TAM).
• To quantify the projected future drying in TAM and assess the reliability of current climate model projections, particularly regarding potential biases.

Study Configuration

• Spatial Scale: Tropical America (TAM), equatorial Pacific, Amazon, and American monsoon regions.
• Temporal Scale: Present-day climate model biases and future climate change projections (implied by "projected rainfall changes" and "global warming").

Methodology and Data

• Models used: 42 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6).
• Data sources: Model outputs from CMIP6.

Main Results

• Amplified equatorial Pacific warming induces a Gill-type atmospheric response that suppresses precipitation across TAM by weakening atmospheric ascent.
• This mechanism explains over half of the inter-model spread in projected TAM rainfall changes.
• The magnitude of projected TAM drying is strongly dependent on the simulated present-day zonal sea surface temperature gradient over the tropical Pacific.
• Climate models systematically underestimate this gradient, likely leading to an underestimation of both equatorial Pacific warming and subsequent TAM drying.
• An emergent constraint suggests a regional mean annual rainfall decline of 46 mm over TAM per 1 K of global warming.
• This constrained projection is approximately 1.5 times the raw model projection and reduces uncertainty by 30%.
• Drought-related risks in the Amazon and American monsoon regions may become more severe than previously estimated.

Contributions

• Identifies a specific atmospheric teleconnection (Gill-type response to equatorial Pacific warming) as a primary driver for projected precipitation suppression in Tropical America.
• Highlights a systematic bias in CMIP6 models regarding the tropical Pacific sea surface temperature gradient, which leads to an underestimation of future TAM drying.
• Provides an emergent constraint that refines projections for TAM rainfall decline, increasing the projected drying magnitude and reducing uncertainty.
• Emphasizes that future drought risks in critical regions like the Amazon may be more severe than previously understood.

Funding

Not specified in the abstract.

Citation

@article{He2025Drying,
  author = {He, Chao and Chen, Xiaolong and Zhou, Tianjun and Kucharski, Fred and Song, Fengfei},
  title = {Drying Tropical America Under Global Warming: Mechanism and Emergent Constraint},
  journal = {Geophysical Research Letters},
  year = {2025},
  doi = {10.1029/2025gl117131},
  url = {https://doi.org/10.1029/2025gl117131}
}