30 Breakthroughs: Climate

November 10, 2021

Drew Shindell

The Human Costs of Climate Change

In 2018, Drew Shindell, Nicholas Distinguished Professor of Earth Science, published a paper that showed up to 153 million premature deaths linked to air pollution could be avoided this century if governments sped up their timetable for reducing fossil fuel emissions.

By projecting the number of preventable deaths—city by city—in 154 of the world’s largest urban areas, Shindell helped reframe global warming as a local health, sustainability and environmental justice issue, and helped drive home for policymakers and citizens alike the benefits of acting sooner rather than later to reduce carbon emissions and limit global temperature rise to 1.5°C.

Kolkata and Delhi, India, could each prevent about 4 million premature pollution-related deaths, the study showed. More than 140 other cities could each prevent between 100,000 and 1 million deaths.

The eye-opening projections, which Shindell calculated using epidemiological models based on decades of public health data, sparked policy discussions worldwide and were prominently cited in the Intergovernmental Panel on Climate Change (IPCC) Special Report: Global Warming of 1.5ºC published later that year.

Will Forests Adapt?

As Earth warms, the fate of many tree species may hang on their ability to keep one step ahead of the rising mercury by spreading, via seed dispersal, to cooler latitudes and elevations.

Research by Jim Clark, Nicholas Distinguished Professor of Environmental Sciences, is helping tilt the odds in the trees’ favor.

Clark harnesses the power of big data and advanced statistical software to track how hundreds of thousands of individual trees from nearly 600 species are responding to a warming climate. The unprecedented scope of his research and sophistication of his software allows him to synthesize decades of raw data and identify patterns that conventional analyses based on averaged measurements can’t see.

Among other discoveries, he’s found that younger, smaller trees increase seed production as temperatures rise, but older, larger trees are less responsive. He’s also found that most species aren’t spreading to cooler climes yet; instead, their ranges are contracting.

These patterns could alter the 21st century landscape, but armed with the models Clark’s developed, the global database he’s curated and insights gained from his ongoing studies, scientists can now much better predict such changes and devise management and conservation strategies to address them.

The Green Divide

Much of Megan Mullin’s career as a scholar of environmental politics has been spent trying to answer two deceptively simple-sounding questions: What shapes our personal beliefs on climate change? And how, in turn, do our beliefs shape our voting decisions?

Through studies designed to tease apart and quantify the influence of a tangle of complex factors, she’s found overwhelming evidence that personal experience, often tied to weather, can be far more powerful than scientific evidence in shaping many Americans’ beliefs.

She’s also found that political ideology and party ID—how strongly we identify as Republicans or Democrats—often trump environmental concerns when we head to the ballot box.

One takeaway from these findings is the idea that scientists need to stop spouting data and instead engage with the public using language and shared values most Americans can relate to, says Mullin, who is the Dan and Bunny Gabel Associate Professor of Environmental Politics. “Rather than discount people’s experiences, we need to communicate science in a way that helps people interpret those experiences as being part of a broader phenomenon,” she says. “Politicians are skilled at this form of communication—we scientists have a lot to learn from them.”

Just How Much Carbon Can Forests Store?

Trees form part of Earth’s first line of defense against climate change by absorbing vast amounts of planet-warming carbon dioxide from the atmosphere through photosynthesis, and sequestering, or storing, the carbon in their trunks, branches, leaves and roots, as well as in the surrounding soil.

Because CO² intake spurs tree growth and larger trees can store more carbon, many scientists in the 1990s theorized that as future atmospheric CO² levels rose under climate change, forests’ carbon storage potential would increase, too, helping to slow the planet’s warming.

Research at the Duke Free-Air CO² Enrichment (FACE) site in Duke Forest has tempered those expectations.

During the 16 years (1994 to 2010) the site was operated, more than 100 researchers conducted studies there, resulting in more than 300 papers documenting the response of loblolly pine ecosystems to artificially elevated levels of CO² that approximated conditions expected by 2050.

“We found some increase in carbon sequestration, but only a limited amount, and nearly all of it in the trees. Soil carbon didn’t change much,” says William Schlesinger, James B. Duke Professor Emeritus of Biogeochemistry.

The upshot, say Schlesinger and Ram Oren, Nicholas Distinguished Professor of Earth Systems Sciences, who were FACE’s co-principal investigators, is that while forests can do a lot to combat climate change, they can’t do it all. Humans need to do their part, too, by acting sooner rather than later to curb fossil fuel emissions and transition to a carbon-free economy.