Tropical Pacific Warming Patterns Influence Future Hydroclimate Shifts and Extremes in the Americas

The eastern tropical Pacific (ETP) Ocean is projected to warm faster than the Atlantic or Indian Oceans in the 21st century, yet this prediction is highly uncertain due to model-observation discrepancies. The potential impacts of this uncertainty on regional terrestrial hydroclimates are largely unknown, which is problematic for climate risk assessments. To address this, we designed novel atmospheric model experiments simulating future global warming with and without enhanced ETP warming, superimposed upon an idealized El Niño-Southern Oscillation cycle. Our results show that enhanced ETP warming significantly influences future terrestrial hydroclimates in several regions across the tropical and subtropical Americas. In southern Mexico, Central America and the Amazon region, enhanced ETP warming exacerbates long term drought trends and extreme drought events, yet the opposite is true in south-central South America. Along the west coast of the continental western United States, the effects of enhanced ETP warming manifest as El Niño-related extreme precipitation anomalies. These findings illustrate how climate impact projections may be misrepresented in conventional multi-model analysis, which does reflect true uncertainty of the future tropical Pacific warming pattern.