New report examines links between greenhouse gas emissions and harms to human health

By Jamie Hansen, Global Health Communication Manager

A new report from the National Academies of Sciences, Engineering, and Medicine details the strongest evidence to date that human-made greenhouse gas emissions cause significant harm to human health and wellbeing.

The National Academies are congressionally chartered and strive to provide independent, objective advice to inform policy with evidence. Michele Barry, MD, senior associate dean of global health, director of the Stanford Center for Innovation in Global Health (CIGH), and senior fellow at the Woods Institute for the Environment, served as one of the 16 members of the committee that produced the report.

The report comes in response to a request for public comment by the Environmental Protection Agency, which is reconsidering the status of its 2009 endangerment finding. This landmark finding determined that human-caused greenhouse gas emissions threatened human health and welfare, and provided the government with the authority to curb these emissions through the Clean Air Act.  Learn more about the endangerment finding in this recent Q&A with Chris Field, PhD, director of the Stanford Woods Institute for the Environment. Woods and CIGH partnered to create and support the new Stanford Center for Human and Planetary Health, which is dedicated to addressing challenges related to climate and health.

The National Academies fast-tracked the report in order to meet the EPA’s deadline for comments of September 22, as the Clean Air Act says that the EPA must consider input from the National Academy of Sciences when assessing risks.

The report, released September 17, reviewed evidence on whether manmade emissions of greenhouse gases to the atmosphere are reasonably anticipated to endanger public health and welfare in the United States, focusing on updates since 2009.

We spoke with Barry about the report’s development and key findings. 

What is the report’s most significant finding?

Our overarching conclusion was that the EPA’s 2009 finding that the human-caused emissions of greenhouse gases threaten human health and welfare was accurate, has stood the test of time, and is now reinforced by even stronger evidence. From the deadly consequences of increased heatwaves and wildfires to the growing threat of vector-borne diseases, we have accumulated tremendous scientific evidence since 2009, which unequivocally shows that human-caused greenhouse gas emissions harm health. 

How did the committee ensure scientific accuracy despite the short timeframe in which the report was developed? 

Scientific rigor was essential to our work. Our committee comprised 16 people from diverse disciplines and backgrounds, ranging from academic researchers to a retired Chevron advisor and retired US Navy rear admiral. We relied on peer-reviewed scientific assessments and formed our strongest conclusions where multiple independent lines of evidence agreed. The report itself was then peer-reviewed by 15 independent experts and an official monitor. Finally, we sought and received more than 200 public comments, all of which we considered and tried to address. 

What were your contributions to this report?

I was tasked with examining the relationship between greenhouse gas emissions and threats to human health in the US. We found that climate change intensifies risks to humans from exposure to extreme heat, wildfire smoke, ground-level ozone, and insect- and water-borne diseases, while also increasing the risk for numerous noncommunicable diseases. These contributions wouldn’t be possible without numerous Stanford investigators who have done significant work to understand the health impacts of various climate change-related phenomena. 

For instance, Minghao Qiu, PhD, a former Stanford-LSHTM Human and Planetary Health Fellow, Marshall Burke, PhD, Stanford professor of Environmental Social Sciences, and other Stanford researchers recently found that wildfire smoke could cause over 70,000 excess deaths per year in the US by the 2050s. Britt Wray, PhD, also a former fellow and now Director of CIRCLE at Stanford Psychiatry, has contributed significantly to our understanding of how climate change is harming the mental health of our young people. Erin Mordecai, PhD, an associate professor of biology, and others have demonstrated that changing temperature and precipitation patterns are driving an increase in vector-borne disease risk, including in the U.S. This includes a growing threat of dengue fever and the expanding range of lyme disease. Climate change also damages renal function, particularly in farmworkers exposed to extreme heat – something Stanford nephrologist Shuchi Anand, MD, and her colleagues are examining in the Central Valley. Additionally, Woods Institute for the Environment Director Chris Field has done pioneering work to understand climate change and possible solutions.

What are your concerns for climate effects on human health and wellbeing in the future?

I think we would see an increase in infectious vector-borne diseases, including tick-borne diseases and mosquito-borne diseases such as dengue fever. Dengue was historically only found in the U.S. by travelers who acquired it outside the country. Recently, however, we’ve seen cases in non-travelers in Texas, Florida, Arizona, Hawaii, and even California. We’d likely see increases in cardiac-related deaths, respiratory complications, and asthma attacks resulting from wildfire pollution and extreme heat. We’d continue to see declines in mental health with exacerbation of depression, suicides, and psychosis. We might see an increase in adults and children suffering from “eco-anxiety” about climate. 

While adaptations can help people cope with these impacts, they cannot remove the risk of harm. Many of these harms will not only fall disproportionately on vulnerable populations in the U.S., such as older adults with multiple chronic diseases and outdoor workers, but also on those without means for adaptation measures such as air-conditioning or home air purifiers. Wildfires and extreme weather events will become the new norm.