Resilience and Adaptation Strategies Can Address the Impacts of Climate Change


Feb 26, 2019

Skyline of Pittsburgh, Pennsylvania, illustration by Malte Muller

Skyline of Pittsburgh, Pennsylvania

Illustration by Malte Müller

By the end of this century, Chicago could face the kind of searing summer heat that Las Vegas sees now. Phoenix could hit 110 degrees, 60 or more days a year.

That's not wild speculation. It's the official position of 13 federal agencies on climate change, released late last year with a warning: Local governments need to do more to prepare. Every road they build, every storm drain they put in, will have to hold up under conditions that modern civilization has never seen.

How do you plan for that? Researchers at RAND have been working on that problem for years now. Their solution: Don't try to guess what the future might bring; imagine an entire range of possible futures, and then look for solutions that work regardless of which one comes to pass. If that sounds complicated, it is. So for now, just consider the Pittsburgh sewer system.

Anticipate New Climate Threats and Impacts

Lisa Werder Brown begins her kayak tours of Pittsburgh rivers with a safety briefing: Don't touch your face. Keep your hand sanitizer close. And take a good shower when you get home. She's the executive director of Watersheds of South Pittsburgh, and if someone can flush something down the toilet, she's seen it in the rivers. “We get a little bit of rain,” she says, “and it just comes gushing out.”

Like many older American cities, Pittsburgh relies on a combined sewer-stormwater system that was state of the art about a century ago. Today, it is old, leaky, and so overwhelmed that it overflows almost every time it rains, sending a mixture of raw sewage and stormwater into the rivers. The region is under a federal mandate to address the problem, a project that will likely cost billions of dollars.

In the past, engineers would have looked to the historical record to figure out how much capacity they needed to build into the system. They would have calculated annual rainfall averages, made note of what a 100-year storm could do, and planned accordingly. That doesn't work anymore.

“The assumption that current and future climate threats and impacts will resemble those of the past is no longer reliably true,” warned the National Climate Assessment released last year by the U.S. Global Change Research Program, on behalf of 13 federal agencies. The report is available online at

Climate change, it found, is already generating storms, heat waves, and droughts beyond the range of historical norms. “Failure to anticipate and adjust to these changes,” it said, “could be costly.”

A lead author of that part of the climate report, Robert Lempert, is a principal researcher at RAND, where he directs the Frederick S. Pardee Center for Longer Range Global Policy and the Future Human Condition. In 2003, he and colleagues Steven Popper and Steven Bankes published a book called Shaping the Next One Hundred Years. In times of great uncertainty, they wrote, computers could help decisionmakers find their way by modeling where different paths would lead under thousands of possible scenarios.

With the right tools and approaches, you can acknowledge uncertainty and say, 'Here is a set of actions we can take that makes sense no matter what future comes to pass.

Share on Twitter

Robert Lempert

“People often assume that uncertainty is debilitating, that decisionmakers can't act when they aren't sure about the future,” said Lempert, whose work on climate change earned him a share of the 2007 Nobel Peace Prize. “But with the right tools and approaches, you can acknowledge uncertainty and say, 'Here is a set of actions we can take that makes sense no matter what future comes to pass.'”

Local governments, though, struggling with big, expensive decisions in the face of climate change, need something more than computer models. They also need public buy-in. Working with a grant from the MacArthur Foundation, Lempert and other researchers developed a decisionmaking framework to help local governments think through climate change. Its purpose is to cut through the politics and get people talking about ideas and solutions, which can then be fed into the computers.

The framework flips traditional decisionmaking on its head. To understand how, imagine buying a new family car. You think about what the next few years are likely to bring, and then buy the car that you think will best meet your needs. The idea here is like selecting the car first, and then running it through hundreds or thousands of possible scenarios—children? a move? a new job?—to see how well it holds up.

The framework allows communities to stress-test ideas and weigh the trade-offs, without requiring everyone to agree from the start on a single vision of the future. It gives them a way to think through low-regret changes they can make, and what it would take to pursue more transformative changes. It's a way through uncertainty on decisions involving many voices and different jurisdictions—a way forward for a place like the greater Pittsburgh region.

In recent years, the question of how to fix the sewage problem there had become a fierce public debate. One side favored building huge concrete tunnels to trap and store stormwater, in addition to a planned expansion of the region's sewage treatment plant. The other wanted more focus on green solutions, like grassy catch basins or rain-permeable pavement. Neither side had looked up from the immediate problem to see what was on the horizon.

As the snow melts, higher water levels and pollution/trash can be seen on the Allegheny River from the North Shore of the City of Pittsburgh, photo by bgwalker/Getty Images

As the snow melts, higher water levels, pollution, and trash can be seen on the Allegheny River.

Photo by bgwalker/Getty Images

“We essentially kicked up these conversations,” said Jordan Fischbach, the codirector of RAND's Climate Resilience Center, who led the Pittsburgh project. “Listen, if you're going to make these billion-dollar investments, let's do everything we can to get it right.”

He and other researchers worked with local officials to organize a series of community meetings. They brought in engineers and technical experts, other local leaders and community groups.

They asked: What do you want to accomplish? What policy levers can you pull to make it happen? And what does success look like? A consensus began to emerge: People wanted solutions that would not just address the stormwater and sewage problems, but also provide other community benefits, be cost-effective in the long run, and avoid burdening ratepayers with further public debt.

Modeling Effective Solutions

To drive those discussions, the researchers ran nearly 5,000 computer simulations of Pittsburgh's future, ranging from business-as-usual to cataclysmic change. They found that expanding the treatment plant would be the most effective solution under most scenarios. But the green infrastructure ideas were increasingly effective—and increasingly cost-effective—as the climate changed and the system had to handle more rain.

The computer models also revealed that the problem was already much worse than anyone had thought. Officials had estimated that around 9 billion gallons of combined sewage and stormwater were spilling into the rivers every year, based on historical averages. RAND's models, using more recent data, put the number closer to 11 billion.

“It was quite clear that things have changed,” said James Stitt, the sustainability manager of the Pittsburgh Water and Sewer Authority, which has expanded its plans and put a greater focus on green infrastructure, partly in response to the study findings. “When you build stuff in this industry, it's supposed to last a hundred years. What's the next hundred years going to bring?”

RAND experts hope to make their framework a national norm for thinking through the uncertainties of climate change—a new standard for urban planning.

Share on Twitter

RAND researchers have tested their framework in two other metro areas, so far. In Broward County, Fla., a team led by David Groves, co-director of the RAND Center for Decision Making Under Uncertainty, identified an inland commercial area as vulnerable to future flooding. Weeks later, to the surprise of local officials, a massive storm left a mall parking lot there under a foot of water. In Sacramento, Calif., the framework is helping transportation planners pursue aggressive greenhouse gas reduction targets while also enhancing mobility.

The researchers are now working to line up funding and partnerships that would allow them to help other urban areas plan for the future. They hope to make the framework a national norm for thinking through the uncertainties of climate change—a new standard for urban planning.

“This is a complex problem, but we didn't want to just keep standing up and saying it's a complex problem,” said Debra Knopman, a principal researcher at RAND and expert on infrastructure planning, who helped lead the development of the framework. The question facing local governments now, she said, is, “Can you still see a path forward that will do well under a wide range of possible future conditions, and not run you off the side of the road into a ditch?”

That ditch, after all, probably spent a good part of 2018 collecting water. More than two dozen U.S. cities received more rain this past year than they ever had before. With nearly 20 inches more than its historical average, Pittsburgh was one of them.

Doug Irving