Rebecca Saari: Exploring the Energy–Climate–Air Quality Nexus

Rebecca Saari: Exploring the Energy–Climate–Air Quality Nexus

Climate policies have traditionally been slow to gain political traction, possibly because the climate benefits of cutting carbon dioxide emissions aren’t felt immediately or on the local level where cuts are made. However, there is one little-discussed side-effect of reducing emissions that does produce immediate local benefits—cleaner air.

Rebecca Saari, who will receive a Ph.D. in Spring 2015 from MIT’s Engineering Systems Division, studies the connection between policies that target greenhouse gas emissions, local air quality, and the accompanying health benefits. Climate policies lead to better regional air quality because the sources that emit carbon dioxide tend to be some of the dirtiest sources of air pollution, like the compounds that contribute to soot and smog. Cutting emissions from these sources lowers both types of pollution, which in turn lowers the rates of health problems like heart attacks and asthma.

“This connection might be surprising, because we don’t often think about air pollution reduction as a major benefit of greenhouse gas mitigation,” Saari says. “Mitigating climate change can be much more locally beneficial than we realize.” 

The drop in air pollution that accompanies a climate policy is often referred to as a cobenefit of the original policy, since the air pollution was not directly targeted by the policy. Considering these cobenefits can add new perspective to a discussion of the costs and benefits of climate policy, Saari says, because the effects of lower air pollution are mainly felt in the near term, and in the same region where cuts are made.

Creating Effective Policy

At the Joint Program on the Science and Policy of Global Change, Saari is working on an unusual sort of cost–benefit analysis. She compares the estimated costs of implementing climate policies to the resulting savings from avoided health expenses related to air pollution, like emergency room visits or missed work. Health problems like these end up costing the economy in healthcare costs, and lost economic productivity.

Modeling these costs and benefits across the economy is a huge undertaking, due to the multiple connected systems involved. Often, researchers studying this issue use separate modeling frameworks for each part of the issue, due to its complexity. Working with MIT Prof. Noelle Selin, Saari developed a method to evaluate both the costs and savings associated with different climate policies. The technique uses a single framework to calculate the effects across all of the areas affected by the policy.

“We’re trying to create a more consistent framework, so we’ve integrated the health effects of cleaner air into the economic level of our framework.” says Saari. “We look at the economic effects of having a healthier workforce. So we’re really looking at impacts to labor and lost productivity.”

Saari is also studying how the air pollution benefits of climate policies vary across regions and income levels. This is a complicated problem, since the answer depends on how many people are living close to emissions sources, what type of fuel is used in nearby power plants, and how states and regions choose to implement climate policies. Saari explains that there can be big benefits to looking at these connections holistically.

“Air quality is one component of a larger set of global sustainability challenges. It’s one thing to try and improve air quality as an isolated issue. It’s another to try to create useful, cost-effective policy that addresses multiple challenges like the economy, equity, and other environmental issues.”

Saari is tackling this problem in her doctoral thesis, which evaluates the air quality impacts and health cobenefits of energy and climate policies, including carbon dioxide limits on existing power plants similar to the US EPA’s Clean Power Plan. She
is exploring how the magnitude and distribution of health benefits differ under different policy scales, from national to state-level implementation; and comparing when national or regional trading is allowed, and when states must make reductions locally. Preliminary results show that when national trading is allowed, the health benefits can outweigh the costs of reducing emissions. However, this effect appears to vary from region to region.

In addition to exploring the costs and benefits of reducing emissions, Saari is studying how climate policy influences air pollution hot spots, or areas where pollution levels are dangerously high. She is assessing if allowing regional trading will shift the location of hot spots, or even create new ones, compared to state-level trading.

“When it comes to carbon dioxide, it doesn’t matter much where it’s emitted. Its contribution to global warming is the same.” Saari says. “But when it comes to air pollution, in terms of its health effects, it really matters where it’s emitted. We want to know if the choice between regional and state-level trading can inadvertently lead to new hot spots.”

Engineering Roots

The desire to address system-wide challenges brought Saari to MIT, but she wasn’t always interested in such a large-scale approach. She began her career as an engineer designing technology for controlling pollution in power plants.

As a master’s student at the University of Toronto Saari designed an optical sensor to improve combustion efficiency and pollution control in industrial furnaces. The sensor was tested at the Nanticoke Generating Station in Ontario, Canada, which was the largest coal-fired power plant in North America until it closed in 2013.

“We stuck it right at the furnace window, so the sensor had to be very robust and simple,” she said. “It was basically a spectrometer that tried to use spectra to estimate ratios of carbon monoxide and carbon dioxide. It was meant to help monitor the steelmaking process, but we found it could be used to estimate emissivity in coal-fired power plants.”

After graduation, Saari joined an engineering firm, where she worked as an air quality engineer on projects related to pollution control design and regulatory compliance. Working on projects in different regions, she noticed that regulations could vary vastly from place to place. She began to wonder why, and if policy grounded in science could address the bigger picture. The new interest made perfect sense to Saari, who sees her work on air pollution as an intuitive progression of her life-long interest in the environment, and her engineering background.

“I’ve always been interested in the natural environment, and while working on these engineering projects, you confront the intersection of the natural environment and the human environment,” Saari says. “Air pollution is an interesting topic in natural science, but it’s a human problem with human impacts. This is what brought me to exploring the human impacts of ‘natural science’ problems like air pollution.”

Rebecca Saari will receive her Ph.D. from MIT's Engineering Systems Division in Spring 2015. After that, she hopes to continue studying the connections between energy, climate, and air quality.