Climate Change and Health: The need for evidence-based approaches
Climate change is rapidly altering health outcomes worldwide, yet medical and public health responses remain insufficiently evidence-based, according to researchers from the University of Washington. Their analysis, published March 10 in JAMA, highlights critical gaps in understanding and addressing climate-related health effects and calls for a more systematic approach to building resilience in healthcare systems.
The paper, authored by Jeremy J. Hess, MD, MPH and Kristie L. Ebi, PhD, MPH from the Center for Health and the Global Environment at the University of Washington, argues that while clinicians, scientists and policymakers may assume efforts to manage climate change health risks are evidence-based, this is not yet reality.
“The medical field has not fully assimilated evidence from observed and projected effects of climate change on health,” the authors write. “This fact, along with insufficient financial investment in developing and implementing effective health protection, leaves communities vulnerable to preventable climate-sensitive conditions.”
Direct health impacts already documented
The researchers point to substantial evidence demonstrating climate change’s direct health effects. These include consistently quantified morbidity and mortality from extreme heat, wildfire-related air pollution, infectious diseases (including dengue, malaria, Lyme disease, and various bacterial infections), floods, and other extreme weather events.
A 2014 World Health Organization assessment estimated climate change would cause 250,000 excess deaths annually by 2030 from just a small subset of climate-sensitive diseases. However, the authors note this figure “was almost certainly a substantial underestimate” as it excluded numerous other known climate-sensitive conditions, including more than half of known human infectious diseases with documented climate sensitivity and climate-sensitive mental health effects.
The paper also highlights indirect health impacts through effect modification, such as increased HIV infection risk associated with climate-related food insecurity resulting from drought, pest infestations, or severe weather exacerbated by climate change.
Future projections even more concerning
Looking toward century’s end, the health consequences grow more severe. Temperature increases of 4°C above pre-industrial levels may occur by 2100, potentially causing unprecedented effects on natural and human systems.
“There is a high risk of extinction for nearly half of the world’s insect species at warming of 3.2°C,” the authors warn. “Temperature increase of 3 to 4°C is expected to result in loss of nearly all coral reefs, collapse of ocean food sources, and widespread plant and animal extinctions.”
These environmental disruptions will have cascading health consequences through reduced productivity, migration, direct loss of life from extreme events, food and water insecurity, and infectious disease outbreaks. The medical community can expect these effects to manifest first as slower progress toward global health priorities, followed by reversals of hard-won gains in areas such as malaria elimination and access to essential healthcare.
Evidence gaps in climate-health science
A central issue identified in the paper is the minimal incorporation of climate change science into global risk assessments such as the Global Burden of Disease Study, national assessments like Healthy People 2030, or local Community Health Needs Assessments required of nonprofit hospitals and health systems in the US.
The authors emphasize that additional evidence is urgently needed to support fundamental aspects of medical and public health practice for climate-sensitive conditions, including prognosis, prevention, and effective interventions. For instance, they note the “paucity of evidence for interventions that reduce respiratory and cardiovascular effects of wildfire smoke exposure” which limits the development of evidence-based treatment protocols.
Clinical challenges in a changing climate
While diagnosing climate-sensitive conditions like heat-related illness may not be inherently challenging, the changing geographic distribution of various infections requires new diagnostic approaches and updated clinical reasoning. Clinicians need to adjust pretest probabilities for climate-sensitive diseases based on geographic location as these patterns shift.
The effectiveness of common interventions, such as fans for protection against heat-related illness or heat early warning systems, requires better evidence to support practice recommendations. The authors suggest using metrics like “number needed to treat” to prioritize interventions according to efficacy, and employing meta-analyses to guide policy development.
When sufficient evidence becomes available, they recommend updating practice guidelines with recommendations for clinical care and implementing relevant health protections, such as guidance for screening patients at risk of heat-related illness, treatment protocols, and discharge planning during extreme heat events.
Surveillance and system resilience
The paper highlights significant gaps in surveillance for climate-related health effects. While standardized approaches for tracking climate-related disease and injury are lacking, existing methods can be employed to monitor outbreaks of climate-sensitive infectious diseases following extreme weather events and enhance surveillance for heat-, flood-, and wildfire-related health impacts.
“Attribution analyses using counterfactuals and quantifying health loss and damage” could strengthen surveillance, the authors suggest. “Such quantification would clarify the financial losses from climate-related population health effects and strengthen the argument for investments to support preventive measures.”
Healthcare systems must become more resilient to challenges posed by extreme weather, including facility damage, staff shortages, supply chain disruptions, and surges in care demand. The authors propose developing measures of resilience, such as the proportion of essential services maintained one year after an extreme event, to help facilities prepare for climate threats like sea level rise and support risk assessment before major capital investments.
Recommendations for clinicians and health systems
The paper offers concrete recommendations for medical professionals seeking to incorporate climate considerations into practice:
- Educate themselves about climate change health effects through continuing education, resources from the Global Consortium on Climate and Health Education, government publications, and professional societies
- Incorporate social and environmental history into clinical practice
- Encourage health systems and public health agencies to use environmental information (weather data, urban heat island intensity, tree cover, greenspace) alongside patient demographics to identify those at higher risk for climate-sensitive conditions
- Advocate for insurance coverage of evidence-based treatments addressing climate change, such as energy subsidies for heating and cooling
- Question healthcare administrators about greenhouse gas emission reduction efforts and plans to increase resilience to climate-related extreme weather events
The authors emphasize that building and implementing an evidence base takes time, but rapid progress is possible through innovations that support screening at-risk populations, updating treatment protocols, developing new therapies, implementing scenario-based planning for health system operations, and enhancing surveillance.
“Incentives such as federal support for reductions in health system emissions, investments in resilience of communities and health systems, and applying environmental data to support health care delivery have potential to prevent avoidable morbidity and mortality,” they conclude. “Given the rapid pace of climate change, there is no time to waste.”
Reference:
Hess, J. J., & Ebi, K. L. (2025). An Evidence-Based Approach to Climate Change and Health. JAMA. Published online March 10, 2025. doi: https://doi.org/10.1001/jama.2024.27927
