A very recent study released in JAMA (Climate Change: Challenges and Opportunities for Global Health) provides a very thorough review showing how climate change affects human health. Perhaps more importantly, the paper also describes how tackling climate change leads to many health and economic benefits.


Authors Jonathan Patz, Howard Frumkin and colleagues combined a survey of the current literature with measured and projected changes to climate to assess health risks associated with climate change. They report many things that we already know. For instance, some adverse health effects from climate change are heat-related (such as heat stress, increased cardiac arrests, reductions in work productivity, to name a few).

Others, such as decreased respiratory health (from changes to ground level pollution associated with climate change or increases in pollens for example), increases in infectious diseases, decreased food security, and more mental stress are just some lesser reported effects we are seeing and will continue to see. The authors conclude,

Evidence over the past 20 years indicates that climate change can be associated with adverse health outcomes. Health care professionals have an important role in understanding and communicating the related potential health concerns and the co-benefits from reducing greenhouse gas emissions.

Dr. Jonathan Patz

First let’s talk more about these health impacts, then we will get to so-called co-benefits.

It’s clear that some changes are happening to our climate and weather. For instance, heat waves, floods, extreme precipitation, and droughts are happening with greater severity in different parts of the globe. These changes, associated with human emissions of greenhouse gases, can be dealt with by either mitigation (stopping climate change), adaptation (dealing with climate change as it occurs), or both. The authors propose various adaptation strategies including more robust infrastructure, increased public green spaces, and white roofs (as just three examples).

Information about extreme heat waves was determined from downscaled climate models that take global or regional climate information and bring it to a more local level. They also obtained ground level temperature and ozone measurements from the US Environmental Protection Agency and nicely show that temperature and ground-level ozone are tightly connected. It should be noted here that ozone in the upper part of the atmosphere (often termed the ozone layer) helps us by blocking high-energy solar radiation which can cause a variety of health effects. However, near the ground, in the air we breathe, ozone is a harmful pollutant.

With the information described above and from other literature, the authors report that the health impacts of a warming planet can be significant – they can also be under-reported. For instance, during very hot episodes, deaths recorded to cardiac arrest may actually be caused initially by elevated body temperatures – although the officially reported cause of death may not reflect this fact. But, even with the under-reporting of heat-related health impacts, we learn that these deaths exceed fatalities from all other weather events combined. This was an astonishing finding; I work in the area of biological heat transfer and yet I was surprised by the numbers.

The authors report that by the end of the century, “more than 2000 excessive heat-wave related deaths per year may occur in Chicago.” They also report that mega-heat waves may increase by 500-1000% in Europe over the next few decades. Likewise, days with high temperatures (above 90–100°F) will increase significantly in major cities.

But it isn’t just heat, there are many other health impacts that should concern us. For instance, the broad category of respiratory disorders has seen a lot of recent research. Most of that research has focused on either ozone (mentioned already) or airborne particulates which can be inhaled during respiration. The authors of the paper discuss how changes to emissions and temperatures affect these pollution levels. In fact, even if we reduce particulate pollution, the changing climate will cause a respiratory “climate penalty” that must be prepared for.

Other health issues discussed are allergens and pollen, increases in infectious diseases, and vector-borne diseases, reduced food security, mental health, and climate-displacement problems. I was particularly interested in the report on water-borne diseases because it is an area of my own research. I am involved in projects to provide pasteurized water to impoverished areas or regions hit by disasters or civil strife.

What we have found, and what the research shows, is that it is difficult to keep pathogens out of a community water source. Some sources, like surface waters, streams, lakes, rivers, or shallow wells can be expected to contain bacteria, viruses, protozoa, and other pathogens which can cause diarrhea and death, particularly in small children. However, when extreme precipitation events occur and short-term flooding results, otherwise clean water sources become contaminated. While estimates vary widely, each year more than 1 million children die from diarrhea and the number is likely far higher. Reducing greenhouse gas emissions while simultaneously improving water infrastructure will help alleviate flood-related water contamination.

But as with other studies, this is not all doom-and-gloom. The important point is there is something we can do about the problems. Of course, we can rapidly implement smart policies that encourage more efficiency in our energy systems. We can also speed the implementation of clean and renewable energies. But too often, the cost-benefit analysis is focused solely on the energy costs with such plans. Rarely do we think of the other benefits that might be achieved by taking smart actions.

As an example, the study finds that increases in energy efficiency and renewable energy generation will cause a reduction in other pollutants such as nitrogen oxide and sulfur dioxide (aside from carbon dioxide). Such reductions would result in human health benefits that must be considered in the calculus. Additionally, dealing with black carbon or other short-term greenhouse gases would reduce premature deaths and improve crop yields. Putting in urban green spaces and cooling cities with white surfaces would increase worker productivity and urban life quality and improve health by promoting exercise.