Climate Anomalies’ Enduring Impacts on U.S. Mortality and Health Landscape

December 2025

Author(s)

Yanbin Xu, PhD, FRM

Wenjun Zhu, FSA, CERA, PhD

Tianxiang Shi, FSA, MAAA, PhD

Executive Summary

This report establishes a U.S.-focused, policy-relevant framework to quantify how El Niño–Southern Oscillation (ENSO) anomalies affect public health, using cause-specific mortality as the primary outcome and a distributed-lag econometric design supplemented by life-table attribution and economic valuation. This framework measures both short-run and persistent effects in historical data, attributes life-expectancy changes to individual causes, monetizes welfare losses, and projects future burdens under alternative climate pathways.

Key findings are threefold. First, El Niño persistently impedes mortality improvement in major diseases, most notably circulatory system diseases and external causes, with effects that intensify among middle and older ages. Second, the 1982–83 and 1997–98 events produced substantial life-expectancy losses and multi-trillion-dollar welfare costs, concentrated in circulatory causes. Third, under intensified ENSO variability, mid-century to end-of-century projections indicate material erosion of U.S. life-expectancy gains, with growing scenario-dependent uncertainty under higher emissions.

The main insights and implications are summarized as follows:

Interpretation and mechanisms. The pattern of ENSO-health links is consistent with climate and behavioral pathways: heat and humidity stress and degraded air quality elevating cardiovascular risks; and environmental and systemic stresses increasing injury and external-cause mortality. The signal is persistent, indicating that El Niño’s health burden propagates beyond the event window rather than being fully offset by quick rebounds in mortality improvement.
Position within the literature and actuarial insights. U.S.-based studies have reported ENSO associations with infectious disease hospitalizations and influenza mortality, but findings were episodic and disease-specific. This study extends that line of work with a unified, quantitative national risk model that integrates multi-cause mortality analysis, scenario-based projections, and economic valuation with traditional actuarial framework. It provides the actuarial community with a quantitative evidence base for understanding how climate anomalies shape population mortality assumptions, health trajectories, and insurance exposures.
Granularity and attribution. Through life-expectancy changes decomposition and sub-causes analysis (e.g., heart disease within circulatory; transport accidents within external causes), this study identifies dominant causal pathways and illustrates how age-specific vulnerabilities evolve from immediate to cumulative five-year horizons. These insights enable actuaries and health system planners to refine stress-testing frameworks, longevity models, and capital adequacy projections under climate risk scenarios.

Material

Climate Anomalies’ Enduring Impacts on U.S. Mortality and Health Landscape

Suggested Citation

Xu, Yanbin, Wenjun Zhu, and Tianxiang Shi. Climate Anomalies’ Enduring Impacts on U.S. Health Landscape. Society of Actuaries Research Institute, 2025.

Acknowledgements

The authors’ deepest gratitude goes to those without whose efforts this project could not have come to fruition: the volunteers who generously shared their wisdom, insights, advice, guidance, and arm’s-length review of this study prior to publication. Any opinions expressed may not reflect their opinions nor those of their employers. Any errors belong to the authors alone.

Project Oversight Group members:
Andre Chen, ASA
Andrew Dilworth, FSA, MAAA
Jing Feng, FSA, MAAA
Sam Gutterman, FSA, FCAS, MAAA, CERA, FCA, HonFIA
Rebecca Owen, FSA MAAA FCA
Mark Velkoff, FCAS
Nathan Worrell, FSA

At the Society of Actuaries Research Institute:
Rob Montgomery, ASA, MAAA, Research Project Manager
Barbara Scott, Sr. Research Administrator

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