Back in 2017, the Medical Society Consortium on Climate and Health warned that climate change was making Americans sicker. Dr. Mona Sarfaty, the group’s director, put it bluntly: “Physicians are on the frontlines and see the impacts in exam rooms,” she said. “What’s worse is that the harms are felt most by children, the elderly, Americans with low income or chronic illnesses, and people in communities of color.”
Nearly a decade later, the evidence outlining the grave threat climate change poses to human health has only grown stronger. While many Americans still don’t connect climate change directly to health risks, the data supports the connection: increasingly extreme heat, severe weather, worsening air pollution, shifting insect populations, and food and water contamination are harming–and in some cases, killing–millions of Americans.
Below are some of the major health risks tied to our capricious climate, along with updated research that expands the conclusions from the MSCCH’s 2017 report.
Rising Heat
Extreme heat is one of the most direct (and deadly) health threats created by climate change. Heat waves are becoming hotter, longer, and more frequent. In the U.S. alone, heat-related deaths more than doubled between 1999 and 2023, climbing from around 1,000 deaths per year to more than 2,300 deaths in 2023. Europe has faced similar crises: in 2023, extreme heat killed 47,000 people across the continent, with women and older adults most at risk.
Heat stress can trigger heat stroke and worsen chronic illnesses like heart disease and kidney disease. Certain life-saving medications also reduce the body’s ability to regulate temperature, making heat more dangerous for patients managing conditions such as hypertension or depression. And while staying indoors with fans and air conditioning may provide temporary relief (for those who have access to electricity and AC), it also drives up energy costs across the board and discourages people from healthy outdoor activity.
Natural Disasters
A warming planet fuels stronger storms, heavier rains, longer droughts, and more destructive floods. These disasters take lives directly but also cause immediate and long-lasting ripple effects: injuries, trauma, displacement, and loss of access to clean water, food, shelter, and healthcare. It takes years of dedication and a lot of taxpayer dollars to rebuild and re-home the victims of the world’s natural disasters, with the strain ever-increasing. The U.S. government has spent over $200 billion rebuilding the fallout zone of 2005’s Hurricane Katrina, and even twenty years later, the effort still isn’t finished.
Furthermore, communities already at risk—children, the elderly, the poor, and people with disabilities—are typically hit hardest. In the U.S., regions such as the Southeast, Great Plains, and Southwest are especially vulnerable to weather-based catastrophe. Globally, the WHO warns that health systems in low-resource regions may be pushed past their limits by repeated climate shocks.
If you’re anxious about the toll the increasing number of storms could take on you and your family, check out our brief guide on disaster preparedness here: ‘Hurricane Season is Underway: Are You Ready?’
Air Pollution
Climate change and air quality are tightly connected. Rising temperatures thicken smog, fuel more frequent wildfires, contribute to dangerous bacteria and mold growth indoors, and lengthen pollen seasons. The result: more asthma attacks and respiratory illness, more emergency room visits, higher rates of serious heart and lung disease, and more strain on the American healthcare system.
Air pollution is already a silent killer. The World Health Organization attributes 7 million premature deaths worldwide every year to polluted air. In the U.S., wildfire smoke alone has affected tens of millions of people in recent summers, sending pollution levels in cities like New York, Chicago, and Portland far above safe limits.
Infectious Insects
Warmer temperatures expand the reach of disease-carrying insects. Ticks that spread Lyme disease now inhabit almost half of U.S. counties, up from only 30% in 1998. Mosquito-borne illnesses such as West Nile virus and dengue are spreading northward, with outbreaks now documented in places where they were once rare, including parts of the U.S. Southeast and Midwest.
These shifting patterns put millions more Americans at risk of infections that were once considered region-specific.
Contaminated Food and Water
Climate change threatens both the safety and nutritional quality of our food and water. Heavy rainfall, flooding, and rising temperatures encourage bacteria growth and spread these harmful microorganisms to our crops, contaminating the plants themselves as well as the livestock and humans that consume them. Warmer waters also promote harmful algae blooms and increase toxin levels and heavy metals in seafood, oceans, rivers, reservoirs, and other recreational bodies of water.
Beyond safety concerns, climate change reduces the nutrient density of many staple crops. Higher atmospheric carbon dioxide levels are linked to lower concentrations of key minerals such as zinc and iron in wheat, rice, and other essential foods. Combined with heat waves and droughts that disrupt crop growth and supply chains, even if food is readily available, it may be less nutritious than in previous generations.
Food- and water-borne illnesses are particularly prevalent in regions like the Southwest and Midwest, where extreme heat and variable rainfall patterns are intensifying.
Mental Health and Wellbeing
The psychological impacts of climate change are profound and multifaceted. Extreme weather events—such as wildfires, hurricanes, and floods—have been linked to significant increases in mental health disorders. For instance, a 2023 study found that 92% of individuals exposed to wildfires experienced PTSD symptoms during the subacute phase, and 33.3% reported depression 18 months later.
Beyond direct exposure to disasters, an increasing and pervasive awareness of climate change contributes to what researchers term “eco-anxiety.” A 2023 survey revealed that 60% of young people ages 16-25 reported being very worried about climate change, with nearly half stating that this anxiety affects their daily functioning. Unlike other anxieties, eco-anxiety is tied not only to personal safety but also to global consequences, leaving individuals grappling with the sense of helplessness born of knowing that no single effort will suffice without collective action.
These mental health challenges are not only a response to immediate disasters but also to the chronic stressors associated with long-term environmental changes. Rising temperatures, increased frequency of extreme weather events, and the gradual loss of familiar landscapes contribute to a collective sense of grief and uncertainty about the future.
Addressing the mental health impacts of climate change requires a multifaceted approach, including increased access to mental health services, community support systems, and public education to build resilience. Recognizing and validating the emotional responses to climate change are crucial steps in mitigating the psychological toll on individuals and communities.
Looking Ahead
The World Health Organization estimates that between 2030 and 2050, climate change will cause an additional 250,000 deaths per year globally from malnutrition, malaria, diarrheal disease, and heat stress alone. These figures don’t even account for losses from air pollution, natural disasters, or mental health impacts.
Protecting public health in the face of climate change requires both individual preparedness and systemic solutions. That means stronger healthcare systems, cleaner energy, better infrastructure, and public awareness.
Climate change isn’t just about probabilities on the horizon—it’s a health crisis that is already here.
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This article was updated on 10/2/2025.