Alan S. Miller
5 min readJan 5, 2024

Health Impacts of Climate Change: Enormous and Growing

The Health Community Is Beginning to Raise Alarm Bells

Construction workers are among those suffering from heat extremes. Image credit: OSHA

In 2019, William Salas Jiminez was among many farm workers in California’s central valley who died when high temperatures, in his case from a heart attack. A 2022 summer heat wave in Europe killed an estimated 60,000 people, and last year’s extreme temperatures harmed many more.

The health consequences of climate change are now becoming difficult to ignore. The impacts of extreme temperatures on human health has become a frequent journal topic, and even the focus of a best-selling book, The Heat Will Kill You First, by Jeff Goodell. The federal agency OSHA is currently in a lengthy process begun in 2021 developing a heat standard. Such regulations already exist in some states including California, while others, notably Texas and Florida, have rejected such measures in response to industry lobbying.

In fact, the health impacts of climate change, most obviously from extreme temperatures, have been a serious concern among scientists and medical experts for decades. As early as 1995, the Second report of the Intergovernmental Panel on Climate Change (IPCC), a consensus review of then known science, stated that “Climate change is likely to have wide-ranging and mostly adverse impacts on human health, with significant loss of life.” The authors warned of both direct and indirect effects, including an increase in malaria and other vector borne diseases; however, they acknowledged that quantifying the projected impacts was difficult due to the many factors involved. In the years that followed a few public health experts (notably professors Jonathan Patz and Paul Epstein) did their best to promote awareness of the issue. A leading health journal, The Lancet, has published an annual assessment of progress addressing climate and health issues for many years, most recently in November 2023.

While some donor funded climate finance was dedicated to health issues in the past, the topic was for decades not a major focus of international climate negotiations. For many years, health officials, other than a few representatives of international organizations like the WHO, did not attend climate negotiations. This changed dramatically at COP28. Health officials from more than 100 countries attended the Dubai meetings, along with hundreds more medical professionals, reflecting the increasing attention to climate change in the public health community. Dozens of side events and webinars on climate and health issues took place, many with high-level government officials and sponsorship by leading medical organizations.

One of the COP outcomes was a declaration on climate and health, the first such statement from the annual international climate meetings. In addition to many predictable pledges of more support for research and planning, a formal linkage to healthiness was endorsed through inclusion of health considerations in national climate plans and strategies.

Increasing evidence that health impacts of climate change are increasing and emerging in many forms

Rising temperatures are a great threat in many developing countries, where most of the population have limited or no access to air conditioners and refrigerators at home or in the workplace. In South Asia alone, it is estimated that heat kills tens of thousands of people every year. Cooling is increasingly being understood as critical to development, akin to energy and water. A 2023 analysis found that, across 77 countries, an estimated 1.2 billion people are at high risk due to a lack of access to cooling, with women making up 52 per cent of the high-risk population in rural areas and 54 per cent in urban areas. There are growing calls to recognize access to cooling as a human right.

Climate change impacts human health in a multitude of ways both direct and indirect. Several impacts due to climate change include the spread of malaria and other insect borne diseases, damage to health infrastructure, hunger and malnutrition from declining farm productivity, and injuries and water pollution caused by floods and intense rainfall events. Climate change is one of several reasons crop-killing diseases are spreading globally creating the threat of mass hunger. Heavy rains in California this year are being linked to a range of public health risks.

As the climate changes, the past is no longer prologue; medical authorities are finding that they must be quicker to detect and adapt to new threats. As a recent article on climate related diseases notes, in Peru, dengue is one of several diseases occurring in far greater frequency, thus challenging the ability of the health system to predict and prepare for outbreaks. The country had its worst outbreak of the disease in 2023, with 250,000 cases and over 400 deaths, and officials are implementing new measures in an effort to detect outbreaks much earlier.

Climate and health are also linked through dietary choices. More than a third of greenhouse gas emissions are attributable to the production, consumption, and disposal of food, and a healthy diet — less red meat, more fruits and vegetables — is also better for the climate.

The burning of fossil fuels, the greatest contributor to rising temperatures, is also a source of enormous health effects from the small particles and other emitted pollutants. A 2021 study concluded that more than 5 million people die globally each year from fossil fuel pollution, while there is recent evidence that such pollution also contributes to a range of other conditions including dementia, Parkinson’s disease, and impaired kidney function.

While health issues are first and foremost a social and ethical issue, the economic implications are also enormous. Health care costs related to climate change are easily in the billions of dollars allowing for millions of additional hospital visits. The inclusion of value of life estimates for the millions of premature mortalities was a significant factor in support of EPA regulations to protect the ozone layer. In an analysis done in 1986, the EPA projected 40 million additional skin cancers and 800,000 deaths in future decades due to ozone depletion with a figure of $2.5 million per life lost, equivalent to $4.5 million today. When critics of climate policy claim that out-of-pocket costs and investments are too high, they obviously fail to weigh the costs of inaction — the costs to society of lives lost and other health related expenditures.

So what to do?

The increasing awareness of the health risks of climate change is beginning to generate a response from the public health community. In one promising sign, climate impacts have begun to influence medical education, with courses and specialized training at medical schools. Several medical schools, including the University of Colorado, now offer a diploma in “climate medicine.”

In a subsequent blog post, I will review a range of additional measures to address the health impacts of climate change, some already underway, others at a demonstration stage or merely proposed.

Alan S. Miller

Alan S. Miller is co-author of “Cut Super Climate Pollutants Now!”. His full bio and links to writing are available at