The Center on Food Security and the Environment is a joint effort of the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment.
In warmer temperatures suicide rates increase, leading to concerns about an uptick in suicides as the globe continues to warm. But researchers offer some hope if greenhouse gases get under control.
As global temperatures rise, climate change’s impacts on mental health are becoming increasingly evident. Recent research has linked elevated temperatures to an increase in violence, stress and decreased cognitive function leading to impacts such as reduced test scores, lowered worker productivity and impaired decision-making.
Adding to the concern, a Stanford study led by economist Marshall Burke also finds a link between increased temperatures and suicide rates. The research, published in Nature Climate Change, concluded that up to 21,000 additional suicides will occur by 2050 within the United States and Mexico if unmitigated climate change continues to warm the Earth at the current projected rates.
Suicide is one of the top 10 causes of death in the United States. Unlike other leading causes – which include heart disease, cancer, homicide and unintentional injury – suicide rates have increased rather than fallen over time. And, while there has been a noticeable trend of rising suicide rates in warmer months, up to this point it has been difficult to attribute these changes to temperature, as other factors like day length and social patterns also vary.
Burke and team overcame these obstacles by assembling and examining decades worth of temperature and suicide data across thousands of U.S. counties and Mexican municipalities. To complement the data, they also scanned over half a billion Twitter updates or tweets and looked for language signaling a negative state of mind.
They found that hotter than average temperatures increase both suicide rates and the use of depressive language on Twitter. They also concluded that socioeconomic status had little to no impact, meaning wealth does not help insulate populations from suicide risk.
“One claim you often hear is that it’s the socioeconomically disadvantaged that are going to be affected by climate change. Our results suggest that at least in the case of mental health, impacts are going to cut across the income distribution and could affect any of us,” Burke said.
He and his team then used global climate model projections to predict how future temperatures could affect suicide rates. They found climate change could increase suicide rates by 1.4 percent in the United States and 2.3 percent in Mexico by 2050.Excess suicides by 2050 caused by warmer temperatures if greenhouse gas emissions stabilize consistent with Paris Agreement goals (move the slider to the right), or if emissions continue unabated (move the slider to the left). (Image credit: Sam Heft-Neal)
Given this increasing overall health burden, the researchers assert even small changes in suicide rates due to climate change could result in large human costs. Also, if similar relationships hold true in other countries, where suicide rates are sometimes even higher than in the U.S. and Mexico, changes in the associated global health burden may be much larger.
“Clearly, climate is not the only factor affecting mental health, and many approaches to addressing the growing mental health challenge will have nothing to do with climate,” Burke said. “But we find clear evidence that a warming climate is going to exacerbate the burden of poor mental health and ignoring this evidence is going to cause unnecessary harm and anguish for a lot of individuals and families inside our country and out.”
The way we treat the planet has direct consequences on human health. This series of stories explores some of those consequences and what we can do to lessen the risks.
Solar radiation management is increasingly considered to be an option for managing global temperatures1,2, yet the economic effects of ameliorating climatic changes by scattering sunlight back to space remain largely unknown3. Although solar radiation management may increase crop yields by reducing heat stress4, the effects of concomitant changes in available sunlight have never been empirically estimated. Here we use the volcanic eruptions that inspired modern solar radiation management proposals as natural experiments to provide the first estimates, to our knowledge, of how the stratospheric sulfate aerosols created by the eruptions of El Chichón and Mount Pinatubo altered the quantity and quality of global sunlight, and how these changes in sunlight affected global crop yields. We find that the sunlight-mediated effect of stratospheric sulfate aerosols on yields is negative for both C4 (maize) and C3 (soy, rice and wheat) crops. Applying our yield model to a solar radiation management scenario based on stratospheric sulfate aerosols, we find that projected mid-twenty-first century damages due to scattering sunlight caused by solar radiation management are roughly equal in magnitude to benefits from cooling. This suggests that solar radiation management—if deployed using stratospheric sulfate aerosols similar to those emitted by the volcanic eruptions it seeks to mimic—would, on net, attenuate little of the global agricultural damage from climate change. Our approach could be extended to study the effects of solar radiation management on other global systems, such as human health or ecosystem function.
By comparing historical temperature and suicide data, researchers found a strong correlation between warm weather and increased suicides. They estimate climate change could lead to suicide rate increases across the U.S. and Mexico.
Suicide rates are likely to rise as the earth warms, according to new research published July 23 in Nature Climate Change. The study, led by Stanford economist Marshall Burke, finds that projected temperature increases through 2050 could lead to an additional 21,000 suicides in the United States and Mexico.
“When talking about climate change, it’s often easy to think in abstractions. But the thousands of additional suicides that are likely to occur as a result of unmitigated climate change are not just a number, they represent tragic losses for families across the country,” said Burke, assistant professor of Earth system science in the School of Earth, Energy & Environmental Sciences at Stanford.
Researchers have recognized for centuries that suicides tend to peak during warmer months. But, many factors beyond temperature also vary seasonally – such as unemployment rates or the amount of daylight – and up to this point it has been difficult to disentangle the role of temperature from other risk factors.
“Suicide is one of the leading causes of death globally, and suicide rates in the U.S. have risen dramatically over the last 15 years. So better understanding the causes of suicide is a public health priority,” Burke said.
To tease out the role of temperature from other factors, the researchers compared historical temperature and suicide data across thousands of U.S. counties and Mexican municipalities over several decades. The team also analyzed the language in over half a billion Twitter updates or tweets to further determine whether hotter temperatures affect mental well-being. They analyzed, for example, whether tweets contain language such as “lonely,” “trapped” or “suicidal” more often during hot spells.
The researchers found strong evidence that hotter weather increases both suicide rates and the use of depressive language on social media.
“Surprisingly, these effects differ very little based on how rich populations are or if they are used to warm weather,” Burke said.
For example, the effects in Texas are some of the highest in the country. Suicide rates have not declined over recent decades, even with the introduction and wide adaptation of air conditioning. If anything, the researchers say, the effect has grown stronger over time.
To understand how future climate change might affect suicide rates, the team used projections from global climate models. They calculate that temperature increases by 2050 could increase suicide rates by 1.4 percent in the U.S. and 2.3 percent in Mexico. These effects are roughly as large in size as the influence of economic recessions (which increase the rate) or suicide prevention programs and gun restriction laws (which decrease the rate).
Effects of historical temperature changes on suicide rates are shown for the U.S. and Mexico. (Image credit: Marshall Burke)
“We’ve been studying the effects of warming on conflict and violence for years, finding that people fight more when it’s hot. Now we see that in addition to hurting others, some individuals hurt themselves. It appears that heat profoundly affects the human mind and how we decide to inflict harm,” said Solomon Hsiang, study co-author and associate professor at the University of California, Berkeley.
The authors stress that rising temperature and climate change should not be viewed as direct motivations for suicide. Instead, they point out that temperature and climate may increase the risk of suicide by affecting the likelihood that an individual situation leads to an attempt at self-harm.
“Hotter temperatures are clearly not the only, nor the most important, risk factor for suicide,” Burke emphasized. “But our findings suggest that warming can have a surprisingly large impact on suicide risk, and this matters for both our understanding of mental health as well as for what we should expect as temperatures continue to warm.”
Marshall Burke is also a fellow at the Center on Food Security and the Environment, Stanford Woods Institute for the Environment, Freeman Spogli Institute for International Studies, and Stanford Institute for Economic Policy Research. Solomon Hsiang is also a faculty research fellow at the National Bureau of Economic Research. Other Stanford co-authors include Sanjay Basu, assistant professor of medicine, and Sam Heft-Neal, research scholar at the Stanford Center on Food Security and the Environment. Additional co-authors are from Pontificia Universidad Católica de Chile, Vancouver School of Economics, and the University of California, Berkeley. The research was partially supported by the Stanford Woods Institute for the Environment.
Linkages between climate and mental health are often theorized, but remain poorly quantified. In particular, it is unknown whether the rate of suicide, a leading cause of death globally, is systematically affected by climatic conditions. Using comprehensive data from multiple decades for both the United States and Mexico, we find that suicide rates rise 0.7% in US counties and 2.1% in Mexican municipalities for a 1 °C increase in monthly average temperature. This effect is similar in hotter versus cooler regions and has not diminished over time, indicating limited historical adaptation. Analysis of depressive language in > 600 million social media updates further suggests that mental well-being deteriorates during warmer periods. We project that unmitigated climate change (RCP8.5) could result in a combined 9–40 thousand additional suicides (95% confidence interval) across the United States and Mexico by 2050, representing a change in suicide rates comparable to the estimated impact of economic recessions, suicide prevention programs or gun restriction laws.
David Lobell, an associate professor of environmental Earth system science and a senior fellow at the Freeman Spogli Institute for International Studies, has been named a 2013 MacArthur Fellow and one of Foreign Policy Magazine's 100 Leading Global Thinkers of 2013.
MacArthur "Genius Grant"
Lobell, who is also the associate director of FSI’s Center on Food Security and the Environment, was cited "for unearthing richly informative, but often underutilized sources of data to investigate the impact of climate change on crop production and global food security." He received his doctorate degree from Stanford in 2005 and was appointed to the faculty in 2009.
A pioneer of the emerging field of crop informatics, Lobell is revolutionizing the understanding of the environmental factors controlling crop yields, with a particular emphasis on adaptation to climate change.
His work provides decision makers, for the first time, with critical information about how to adapt agricultural development to climate change.
"I was completely surprised by this recognition, but am really excited by the opportunity it presents," said Lobell, who is also a senior fellow at Stanford Woods Institute for the Environment. "To have the MacArthur Foundation recognize the value of taking new approaches and the importance of the topics of hunger and food production is deeply gratifying."
Lobell's research focuses on identifying opportunities to increase yields of crops including wheat and corn in major agricultural regions, with projects currently underway in Africa, South Asia, Mexico and the United States.
"I'm interested in how to feed the world and protect the environment at the same time," he said. "While there are many theories about how to do that, my work tries to test these theories, often using data that were collected for completely different reasons."
The citation emphasized Lobell's work on understanding the risks of climate change, and options for adaptation. "Climate change is one of the reasons for concern about feeding people in the future, but it's not insurmountable if good decisions are made," he said.
When asked how he would use the funding, Lobell said he would not rush the decision. He said that some of the award would likely relieve him of writing grant proposals. In addition, he said he would consider using some toward more travel.
"A lot of my better ideas in the past have started with travel and interactions with international collaborations," he said. "And there's always a tradeoff between my work travel and family. I now might take my wife and young sons with me on some extended trips."
Foreign Policy's Leading Global Thinkers
In December, Foreign Policy named Lobell one of the 100 Leading Global Thinkers of 2013. The recognition comes for his work "helping farmers feed the world" in a changing climate. Lobell is joined on the magazine's list by fellow researchers working on climate issues, along with prominent public figures like German Chancellor Angela Merkel, U.S. Secretary of State John Kerry, and Pope Francis.
Widely sought throughout the world to provide expert advice, Lobell is a lead author for the Intergovernmental Panel on Climate Change Fifth Assessment Report chapter on food security, to be published in 2014. The IPCC, which won the Nobel Prize in 2007, also made Foreign Policy's 2013 Leading Global Thinkers list alongside Lobell, "for showing that humanity is on the brink of catastrophe" if climate change is not addressed quickly and aggressively.
Lobell studied applied mathematics at Brown University, and before receiving his bachelor's degree in 2000, he spent the summer of 1999 as a research intern at Stanford, developing remote sensing algorithms. He then pursued graduate studies at Stanford, receiving his doctorate in geological and environmental sciences in 2005.
He was a postdoctoral fellow at Lawrence Livermore National Laboratory from 2005-2007, and returned to Stanford as a senior research scholar in the Program on Food Security and the Environment in 2008-2009. He accepted an appointment as assistant professor in the Stanford School of Earth Sciences in 2009.
In addition to his research, Lobell teaches several courses open to both undergraduates and graduate students, including "Feeding Nine Billion," "Climate and Agriculture," and "Global Land Use to 2050," as well as modeling and statistical methods classes.
Lobell received a NASA New Investigator Program Award for 2008-2011. He received the James B. Macelwane Medal from the American Geophysical Union in 2010, awarded for significant contributions to the geophysical sciences by an outstanding scientist under the age of 36.
Nancy Peterson is the chief communications officer for Stanford's School of Earth Sciences. Laura Seaman, communications manager for the Center on Food Security and the Environment, contributed to this article.
Seeds of Sustainability tackles a central challenge of sustainable development: agricultural modernization. It is cutting edge not because the issue itself is new, but rather the level of integration the authors attempted and the innovative process they used. The volume summarizes the findings and reflects on the process of a highly interdisciplinary team of researchers, integrating perspectives from: biogeochemistry, atmospheric sciences, land-use change, institutions, agronomy, economics, and knowledge systems. The foundation of the work is rigorous, grounding its findings in multiple peer reviewed publications, while not hesitating to point out gaps or unresolved issues. Seeds of Sustainability includes an in depth historical analysis, which captures issues of path dependence. It demonstrates both originality and critical reflectiveness in its efforts to engage practitioners in the conceptualization and execution of its research, and the implementation of its findings. And almost uniquely in our collective experience, it speaks seriously, frankly, and insightfully to the challenges of institutionalizing the sort of work it reports on.
The Yaqui Valley is the birthplace of the Green Revolution and one of the most intensive agricultural regions of the world, using irrigation, fertilizers, and other technologies to produce some of the highest yields of wheat anywhere. It also faces resource limitations, threats to human health, and rapidly changing economic conditions. In short, the Yaqui Valley represents the challenge of modern agriculture: how to maintain livelihoods and increase food production while protecting the environment.