A 2023 study from Associate Professor of Geography Justin Mankin’s research group that quantified the global economic fallout of the recurring climate pattern known as El Niño has been recognized as one of the most important new findings in climate science.
The study is included among this year’s 10 New Insights in Climate Science report, or 10NICS, a compendium of pivotal climate research from around the world during the past 18 months. The report highlights studies by more than 80 researchers from 45 countries that assess and project the catastrophic consequences of human-driven climate change on human health and safety, weather, ecosystems and natural processes, economies, and other areas.
The Dartmouth study, published in the journal Science, is one of four papers constituting the report’s fifth insight, which concerns the effect of global warming on large-scale ocean processes. Mankin, who is senior author of the study, conducted it with Christopher Callahan, the paper’s first author and then-Dartmouth doctoral candidate who received his PhD in 2023 from the Guarini School of Graduate and Advanced Studies. Callahan is now a postdoctoral scholar at Stanford.
“The key insight that Chris and I came to is that El Niño is orders of magnitude more costly to the global economy than previously understood,” says Mankin, the director of the Climate Modeling and Impacts Group at Dartmouth.
“Because the hazards from El Niño look a lot like the wider impacts of warming—extreme heat, floods, droughts, and more severe storms—that tells us that our economies are poorly adapted to the climate we have currently, let alone the one unfolding from global warming,” Mankin says. “El Niño, I think, can serve as a test-bed for wider adaptation and resiliency investments in response to climate change.”
The 10NICS report is intended to drive international climate policy, particularly during the 29th United Nations Climate Change Conference, also known as COP29, being held in Azerbaijan next month. Representatives from countries worldwide will discuss—and ideally agree to—concrete steps nations can collectively take to reduce carbon emissions and mitigate—as well as adapt to—the effects of climate change. The international climate treaty known as the Paris Agreement was negotiated at COP21 held in Paris in 2015.
Callahan and Mankin spent two years examining global economic activity in the decades following the 1982-83 and 1997-98 El Niño events and found a “persistent signature” of slowed economic growth more than five years later. They found that the global economy bled $4.1 trillion and $5.7 trillion, respectively, in the half-decade after each El Niño due to devastating floods, crop-killing droughts, plummeting fish populations, and an uptick in tropical diseases.
Using the Dartmouth model, 10NICS estimates that the recent 2023-24 El Niño will cost the global economy $5.7 trillion by 2029.
The study was among the first to evaluate the long-term costs of El Niño. El Niño is the warm phase of the El Niño-Southern Oscillation, the natural cycle of warm and cold temperatures in the tropical Pacific Ocean. El Niño alters weather patterns worldwide and, in the United States, typically results in wetter, warmer winters for the West Coast and a milder hurricane season on the Atlantic seaboard.
A key focus of Mankin’s research is quantifying the financial repercussions of extreme weather caused by climate change—and the potential liability of the polluters accelerating rising temperatures.
In 2022, he and Callahan reported that more severe heat waves cost the world an estimated $16 trillion from 1992 to 2013 due to the effects of high temperatures on human health, productivity, and agricultural output. An earlier paper they published assessed the economic damages individual countries have caused to others by their contributions to climate warming and provided a scientific framework for suing for restitution.
Recent research from Mankin’s group also has found that the U.S. Drought Monitor has not adapted to climate change, that seasonal snowpacks in most of the Northern Hemisphere have shrunk significantly since 1981, and that warmer temperatures are resulting in more home runs in Major League Baseball.
The 10 New Insights in Climate Science report debuted in 2017 ahead of COP23 in Bonn, Germany. It is a joint initiative of Future Earth, the Earth League, and the World Climate Research Programme.