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Radley Horton: Finding Answers and Spreading Messages of Caution and Hope on Climate

radley horton
Lamont Associate Professor Radley Horton. Photo: Lamont-Doherty Earth Observatory

Lamont Associate Research Professor and climatologist Radley Horton is determined. His work — investigating extreme weather events, discerning the limitations of climate models, predicting the current and future ramifications of climate change, and generating adaptation strategies — is matched by his commitment to communicating his findings and the under-appreciated threats associated with global warming.

“It’s real. It’s us. It’s serious. The window of time to prevent widespread, dangerous impacts is closing fast,” Horton recently told a group of business leaders. He believes that to confront climate change effectively, scientists must translate their work clearly and regularly to stakeholders and society’s power brokers.

“We have to meet them in their decision-making context,” he explains.

In the past few years, research from Horton’s group has underscored the impacts of extreme heat on commercial aviation, illuminated how the tree-killing southern pine beetle will expand its range of devastation should minimum temperatures continue to increase (as predicted), and how the combination of hot and humid weather will endanger the health and livelihoods of many global populations. A research paper on this last topic this year captured widespread public attention, especially given the recent trend of record-breaking summer temperatures from one year to the next.

“Within the next two generations, heat and humidity could create an existential threat to some coastal populations who lack access to air conditioning,” says Horton.

Most projections about future intensifying heat waves leave out humidity, which can greatly magnify the effects of heat alone. Horton and his colleagues produced forecasts that the combined impact of heat and humidity will markedly increase in many areas. At times, such conditions may surpass the ability of humans to work outdoors or, in extreme cases, even survive. Health and economies would suffer, especially in regions where people work outside and have little access to air conditioning. Potentially affected regions include large swaths of the already muggy southeastern United States, the Amazon, western and central Africa, southern areas of the Middle East and Arabian Peninsula, northern India, and eastern China.

The research made use of global climate models to map current and future “wet bulb” temperatures, which reflect the combined effects of heat and humidity. (The measurement is made, in principle, by draping a water-saturated cloth over the bulb of a conventional thermometer; it does not correspond directly to air temperature alone.) The study found that by the 2070s, high wet-bulb readings that now occur only once a year could prevail 100 to 250 days of the year in some parts of the tropics. In the southeastern United States, wet bulb temperatures now sometimes reach an already oppressive 29 or 30 degrees Celsius; by the 2070s or 2080s, such weather could occur 25 to 40 days each year, say the researchers.

Lab experiments have shown wet-bulb readings of 32 degrees Celsius are the threshold above which many people would have trouble carrying out normal activities outside. This level is rarely reached anywhere today. But the study projects that by the 2070s or 2080s the mark could be reached one or two days a year in the U.S. southeast and three to five days per year in parts of South America, Africa, India, and China. Worldwide, hundreds of millions of people would suffer. The hardest-hit area in terms of human impact, the researchers say, will probably be densely populated northeastern India.

Horton’s work is global in scope. His ability to convey the concepts of climate change and its potential impact continue to elevate both his profile and that of his profoundly important science.

Radley Horton In His Own Words

Q: What are some of your earliest memories, and do you think your childhood influenced your decision to become a climatologist?

Some of my earliest memories include going up to the top floor of our Brooklyn home to listen to the wind and thunder and watch the lightning with my mom. There was a back window where we could watch that metallic glow the city would get during evening thunderstorms. And I remember falling asleep to the sound of breaking ocean waves during summers on Fire Island. I also used to find comfort in numbers and Atlases, memorizing arcane facts like the most extreme minimum temperatures experienced around the world.

Q: How did you come to choose climate research for your life’s work?

It was not a linear path. While extreme weather was always a fascination growing up, I actually studied liberal arts as an undergraduate, and it was not until a post-undergraduate internship project that involved climate and ecosystems that I realized, in order to make a certain kind of impact, I would need an advanced degree.

Q: You describe your approach to climate research as having a “big picture” perspective. How does this perspective guide the research you pursue?

I think my liberal arts background has helped me to (1) steer towards societally impactful climate research questions; (2) sense how assumptions embedded in detailed quantitative approaches to projections can paradoxically lead to underestimates of the range of possible outcomes; and (3) understand that for many societal decisions, a general picture of how climate may change, rather than precise information, is all that is needed, since climate is one of many factors driving a decision.

Q: You say the window for mitigating the devastating effects of climate change is closing. What would you most want people to understand right now?

I want people to understand these small changes we talk about — the one degree of global warming to date, the less than one foot of sea level rise over the last century — tend to sound like nothing. Actually, these changes have already profoundly modified the frequency with which we experience coastal flooding and already lead to much more dangerous heat extremes than we’ve seen in the past. I want people to understand that the frequency and intensity of extreme events have already changed dramatically due to human activities like fossil fuel combustion and land use change. The change in extreme event statistics to date suggests the urgent need to reduce greenhouse gas emissions and to adapt.

Q: What worries you most about the future of Earth?

I’m worried that we have underestimated how sensitive the climate is to greenhouse gases. I’m worried that we are going to see climate changes occur faster than climate models suggest. If we look, for example, at Arctic sea ice, the late summer ice volume has decreased much faster than any climate models have suggested. That finding opens the door to the possibility that, even if we somehow stabilize greenhouse gas concentrations, we may already be locked into a total loss of late summer Arctic sea ice. That ice loss in turn could have unforeseen consequences on things we take for granted, like the ebb and flow of mid-latitude weather systems, their impact on heat waves, and heavy rain events. I’m concerned about what other monsters lurk in the climate system.

Q: What gives you hope for the future?

I get to instruct undergraduate students every semester as part of Columbia’s undergraduate program in Sustainable Development. And every semester I’m struck by how, in the face of all this daunting data, the majority of students remain optimistic, have a “can do” attitude, and are committed to making the world a better place. They have come to terms with existential questions, but in general they don’t get hung up on those questions. They usually say, “let’s get to work and do our part,” even though, quite frankly, we in the prior generations have unfairly dealt them a poor climate hand. Their work ethic and their technical abilities are so far beyond where I was in college. They are a source of optimism for me because we are going to need a tipping point to break in our favor in the climate solutions space. Their generation can be that transformation, whether through scientific discovery, interdisciplinary solutions, or simply refusing to work for, purchase from, or invest in either fossil fuel majors or those that fail to consider how their assets and mission will be impacted by our changing climate.

This interview was originally published in Lamont’s 2018 Annual Report. 

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Congratulations to our Columbia Climate School MA in Climate & Society Class of 2024! Learn about our May 10 Class Day celebration. #ColumbiaClimate2024

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