Stormy seas: Solomon Hsiang on the link between climate and health

In 2013, a study published in Science came to a stark conclusion: extreme climate events significantly increase rates of violence and civil war - and, ultimately, human health.

Solomon Hsiang, one of the lead authors of that paper, has seen this pattern play out again and again throughout his research. As our climate changes, so does our behaviour – towards strangers, friends, and even ourselves. Quantifying and predicting those behavioral trends, and using those findings to guide policy change, is the guiding principle of Hsiang’s work.

As part of a speaker series sponsored by the Center for Human and Planetary Health, Hsiang, professor of Global Environmental Policy and director of the Global Policy Lab, outlined the central themes of his research on climate and public health – and its real-world policy implications.

“Today, we have a lot of science and computing and a much deeper understanding about how our decisions will impact us in the future,” Hsiang said to Stephen Luby, Faculty Director of the Center for Human and Planetary Health, who moderated the discussion. “We have the insight and the ability to have those discussions, whereas historically, people were literally flying blind.”

Analyzing historical periods going back to 10,000 BCE and spanning every world region, Hsiang and his colleagues found a clear, casual relationship between heavier rainfall or hotter temperatures and human conflict. The strength of climate’s influence is substantial: one standard deviation change in climate leads to a 14 percent increase in group conflict. 

Specific climatic phenomena like El Niño, which heats and dries the tropics, were linked to a doubling of civil conflict rates in affected regions. By treating the equatorial regions most directly impacted by El Niño as a “treatment group” and comparing them to less-affected zones, Hsiang demonstrated that rising temperatures appear to consistently increase instability. These findings align with others analyzing road rage and temperature and Twitter sentiment analysis during heat waves.

Hsiang also pointed to an analysis of self-harm and suicide in the U.S. and Mexico, where he and colleagues found a clear link between temperature and suicide rates. This pattern, Hsiang emphasized, was consistent across borders and demographics. 

According to Hsiang’s research, extreme climate events don’t just increase rates of conflict – they lead to elevated mortality rates long after skies have cleared. 

Using over 80 years of storm data, Hsiang and his team discovered that mortality rates remain elevated in impacted regions for up to 15 years after a hurricane hits. The team also found that these deaths are not typically from trauma, but chronic conditions like cancer and cardiovascular disease. This suggests that social and financial stressors from disaster recovery are silently shaping public health outcomes. 

Returning to the governance implications of his research, Hsiang described efforts to project future mortality caused by rising global temperatures. While wealthier populations are expected to adapt (he pointed to air conditioning as an example), poorer regions are more vulnerable. 

At the end of his presentation, Hsiang encouraged students and researchers to think long-term, build relationships with policymakers, and invest in visual communication to ensure their work can have real-world impact.

“With research, everything has to be pre-thought,” he said. “It has to be like a microwavable meal — packaged, ready to go, and then it sits on the shelf. We try to think about the questions that people in the future will be asking and try to develop answers before anyone has actually asked those questions.” 

Stephen Luby is faculty director of the Center for Human and Planetary Health. He is also a professor of Medicine - Infectious Diseases at the School of Medicine and a senior fellow at the Stanford Woods Institute for the Environment and at the Freeman Spogli Institute for International Studies.