Residency · Residency · Preventive Medicine

Climate Change and Health: Mitigation and Adaptation Strategies

Overview

Climate change is the defining public health threat of the 21st century, as documented by the Lancet Countdown. Global average temperature has increased approximately 1.1 degrees Celsius above pre-industrial levels and is on track for 2.5-3 degrees by 2100 without aggressive mitigation. Health effects are both direct (heat illness, extreme weather injuries) and indirect (food insecurity, vector-borne disease expansion, population displacement, mental health deterioration). Climate change exacerbates existing health inequities, with low-income populations, communities of color, and low-income countries bearing disproportionate burdens despite contributing least to the problem. Preventive medicine physicians have important roles in health system adaptation, community resilience building, and advocacy for mitigation policies.

Direct Health Effects

Heat-Related Illness and Mortality

Heat waves are the deadliest weather-related hazard in the United States. The clinical spectrum progresses from heat cramps through heat exhaustion to heat stroke, which is a medical emergency carrying 10-50% mortality. The urban heat island effect makes cities 1-7 degrees Fahrenheit warmer than surrounding areas due to concentrated concrete, asphalt, and reduced vegetation. Vulnerable populations include the elderly, outdoor workers, those without air conditioning, and individuals with chronic diseases. Adaptation strategies include heat action plans, cooling centers, early warning systems, and urban greening programs.

Extreme Weather Events

Climate change is increasing the frequency and intensity of hurricanes, floods, droughts, and wildfires. These events cause direct injuries and deaths while damaging infrastructure that supports healthcare, water supply, sanitation, and transportation. Wildfire smoke generates fine particulate matter (PM2.5) that causes respiratory and cardiovascular disease exacerbations over enormous geographic areas far from the fires themselves. Post-disaster conditions including contaminated water and crowded shelters facilitate infectious disease outbreaks.

Air Quality Degradation

Higher temperatures accelerate ground-level ozone formation. Wildfire smoke events increasingly affect air quality across entire regions for extended periods. Climate change is producing longer and more intense pollen seasons as allergenic plant growth is stimulated by elevated CO2 and warmer temperatures. These changes exacerbate asthma, COPD, and cardiovascular disease.

Indirect Health Effects

Vector-Borne Disease Expansion

Warming temperatures expand the geographic range of disease vectors including mosquitoes and ticks. Aedes mosquitoes carrying dengue, Zika, and chikungunya are expanding into previously temperate zones. Ixodes tick populations responsible for Lyme disease are moving northward in North America and Europe. Warmer temperatures accelerate viral replication of West Nile virus within mosquitoes. Malaria may re-emerge in highland areas of Africa and Asia where cooler temperatures previously prevented transmission.

Food Security and Nutrition

Heat stress, drought, and extreme precipitation events reduce crop yields. Elevated CO2 concentrations decrease the nutritional quality of staple crops, reducing their protein, zinc, and iron content. Ocean warming and acidification disrupt fisheries. Food price volatility disproportionately affects low-income populations. Warmer and more humid conditions increase mycotoxin contamination of stored grains.

Water Security

Altered precipitation patterns produce more intense rainfall events interspersed with prolonged droughts. Glacial melt threatens water supplies for billions of people dependent on snowmelt-fed rivers. Sea level rise causes saltwater intrusion into coastal aquifers. Flooding and infrastructure failure increase waterborne disease risk.

Mental Health

Eco-anxiety, climate grief, and solastalgia (distress caused by environmental change in one's home environment) are emerging mental health concerns. Extreme weather events trigger post-traumatic stress, depression, and substance use. Agricultural communities face drought-related financial stress and increased suicide rates. Children and young adults are disproportionately affected by climate anxiety.

Displacement and Migration

An estimated 21.5 million people are displaced annually by weather-related events. Sea level rise threatens coastal communities and small island nations. Climate-driven migration exacerbates overcrowding, resource competition, and infectious disease transmission in receiving areas. Health infrastructure in destination communities may be overwhelmed.

Health Co-Benefits of Climate Mitigation

Transitioning from fossil fuels to clean energy reduces air pollution (PM2.5, ozone, NOx, SO2), producing immediate health benefits. Promoting active transportation — walking and cycling — reduces cardiovascular disease, obesity, diabetes, and depression. Plant-forward diets reduce both greenhouse gas emissions and chronic disease risk. Energy-efficient housing reduces respiratory illness and energy poverty. Research indicates that the health co-benefits of climate action may offset or exceed the direct costs of mitigation.

Health System Adaptation

Climate-Resilient Health Systems

Building climate resilience requires health facility preparedness for extreme weather events including backup power, water, and supply chain redundancy. Surge capacity planning must account for heat waves, wildfire smoke events, and storms. Health workforce training should include climate-sensitive diseases. Pharmaceutical and medical device supply chains need resilience planning against climate-related disruptions.

Surveillance and Early Warning

Heat-health early warning systems linked to public health response protocols save lives during heat waves. Syndromic surveillance can track climate-sensitive health conditions. Air quality monitoring and the Air Quality Index system provide real-time health advisories. Vector surveillance programs track the geographic expansion of disease-carrying arthropods.

Healthcare Decarbonization

The healthcare sector is responsible for approximately 4.4% of global greenhouse gas emissions and about 8.5% in the United States. Opportunities for reducing the healthcare carbon footprint include improving energy efficiency, adopting renewable energy, implementing sustainable procurement, managing anesthetic gas emissions, and reducing waste. Health Care Without Harm is a global coalition promoting sustainable healthcare practices.

Mitigation Policy

The Paris Agreement aims to limit warming to well below 2 degrees Celsius, preferably 1.5 degrees. Carbon pricing through carbon taxes or cap-and-trade systems internalizes the health costs of fossil fuel use. The clean energy transition encompasses renewable electricity generation and transportation electrification. Methane reduction targets agriculture, fossil fuel infrastructure, and waste management. Nature-based solutions including reforestation, wetland restoration, and urban green infrastructure sequester carbon while providing co-benefits for health.

<image>A diagram showing the direct and indirect pathways through which climate change affects human health. At the top, "Climate Change" (rising temperatures, extreme weather, sea level rise) branches into direct pathways (heat illness, injuries from storms, air quality) and indirect pathways (vector-borne disease expansion, food insecurity, water insecurity, displacement, mental health). Moderating factors (social determinants, adaptation capacity, health infrastructure) are shown influencing the magnitude of health effects. Arrows connect each pathway to specific health outcomes. Climate and health education diagram.</image>

<image>A world map showing the projected expansion of Aedes aegypti mosquito range under climate change scenarios, with current range in one color and projected expanded range by 2050 and 2100 in additional colors. Inset shows the diseases transmitted by Aedes (dengue, Zika, chikungunya, yellow fever) and the number of additional people at risk. Climate and vector-borne disease education illustration.</image>

Clinical Pearls

Heat-related mortality is largely preventable through public health interventions including early warning systems, cooling centers, and check-in programs for isolated elderly residents. The health co-benefits of climate mitigation are often the strongest argument for policy action — reduced air pollution alone can save thousands of lives annually in the near term. Healthcare itself is a major greenhouse gas emitter, making climate-conscious clinical practice (reducing waste, choosing lower-carbon anesthetics, supporting telehealth) an emerging professional competency. Climate change disproportionately harms those who contributed least to the problem, making it fundamentally a health equity issue. For board preparation, understand the direct and indirect health pathways of climate change, the concept of co-benefits, and the distinction between adaptation and mitigation strategies.

References

• Romanello M, et al. The 2023 report of the Lancet Countdown on health and climate change. Lancet. 2023;402(10419):2346-2394.
• Watts N, et al. The Lancet Countdown on health and climate change. Lancet. 2018;391(10120):581-630.
• Ebi KL, et al. Hot weather and heat extremes: health risks. Lancet. 2021;398(10301):698-708.
• IPCC. Climate Change 2023: Synthesis Report. Intergovernmental Panel on Climate Change; 2023.
• Eckelman MJ, Sherman JD. Environmental impacts of the U.S. health care system and effects on public health. PLoS One. 2016;11(6):e0157014.

Read this lecture as Markdown