Viewing climate change as a human health problem


This week, the medical journal The Lancet released its annual “Report of the Lancet Countdown on Health and Climate Change” and a companion brief focused on conditions in the United States. The brief urges action to curb global-warming emissions, arguing that the health impacts of a shifting climate are already being seen in the U.S. and rapidly growing severe. Those include direct effects, such as illness from extreme heat or drowning from floods, as well as indirect and less-obvious ones, like shifting infectious-disease patterns or worsening allergies and asthma from more-intense pollen levels. Renee N. Salas, assistant professor of emergency medicine at Harvard Medical School, ER physician at Massachusetts General Hospital, climate and health expert at the Harvard Global Health Institute, and Yerby Fellow at the Harvard T.H. Chan School of Public Health’s Center for Climate, Health, and the Global Environment, was the lead author of the U.S. brief and an author on the global report. She spoke with the Gazette about the findings.


Renee N. Salas

GAZETTE: Were there examples this year of weather extreme enough to affect people’s health that could be at least partly related to climate change?

SALAS: Yes. Climate change makes it more likely for these events to be more intense. This often translates to worse health outcomes and increased health-system disruption. One way to think about it is that climate change loads the dice. Overall, recent research found more than a third of heat-related deaths in U.S. cities can be attributed directly to climate change. The Pacific Northwest heat wave in June of 2021 was found by climate scientists to be virtually impossible without climate change. It was a catastrophic mass-casualty event estimated to have led to over 600 excess deaths in Washington and Oregon in a week. And there were more than 70 times the number of heat-related emergency department visits when compared to that same time period in 2019. We have an enormous opportunity to limit these harms by acting swiftly and decisively on climate change to protect health and advance equity.

GAZETTE: So we can expect more events that are completely out of the range of normal weather for a region?

SALAS: Climate change is worsening heat waves, making them more frequent, longer, and hotter. It’s amplifying drought and intensifying wildfires. It is supercharging hurricanes, which are slower, wetter, and stronger because of climate change. Climate change is fueling flood risks with increased heavy-rainfall events. It is raising sea levels that contribute to coastal flooding, which is especially of concern here in the Northeast because we are experiencing some of the highest rates of sea-level rise in the country. At the same time, there’s an increased risk that we’re going to have more very extreme events.

The Intergovernmental Panel on Climate Change shows that it’s imperative to urgently transition to a very low carbon-emission pathway if we want to keep temperature rise to below 1.5 degrees Celsius. Even though a 10th of a degree can seem small and insignificant, every fraction has significant implications for health and equity. So an extreme heat event that used to happen once every 10 years in the second half of the 19th century is today three times more likely. When we look at a 1.5 degree versus a 2 degree Celsius temperature rise, this half a degree means the difference between those events being nearly four times versus six times more likely, with an increased chance of even hotter temperatures. This translates to increased illness, suffering, and death.

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