Jareth Holt

MIT researchers demonstrate new approach to designing location-specific emissions-control measures

	Photo: Paul Kishimoto

by Audrey Resutek | MIT Joint Program on the Science and Policy of Global Change

Graduate students from the Joint Program on the Science and Policy of Global Change taught a series of classes in January as part of MIT’s annual Independent Activities Period (IAP) that were designed to bring students and community members up to speed on basic climate science, climate policy, and the state of international climate negotiations.

International climate action

Amanda Giang, a graduate student in the Engineering Systems Division, led a session on January 30 on recent climate negotiations. Climate change is a vexing international problem in part because it is a commons problem—a type of problem which many graduate students may already be familiar with, she said.

A dirty kitchen is an example of a commons problem, said Giang, who has roommates. “We all share the kitchen, so it’s in no one’s best interest to clean the kitchen alone. If I clean the kitchen myself, I have to do all the work while everyone gets the benefit. But if no one cleans the kitchen we all suffer. What we really need is some sort of coordinated collective action, where I take out the trash and my roommate does the dishes.”

Because of this, an international agreement is the best route for action. Giang reviewed the recent history of global climate negotiations, including the UN’s efforts leading up to the next round of talks in Paris this winter, where countries are expected to come to an agreement on post-2020 climate action. Giang also discussed existing greenhouse gas mitigation efforts in the US and China, and the recent emissions deal between the two countries.

Economic measurements

Paul Kishimoto, a graduate student in the Engineering Systems Division, led sessions on January 29 and January 30 on the economics of climate change and climate policy.

Economists measure the effects of climate change as costs, both direct and indirect. As an example, Kishimoto asked the class to consider how statistically warmer weather might affect a runner who goes jogging on the Charles. If the runner goes jogging when it’s too hot and gets heat stroke and has to go to the hospital, it is a cost directly related to climate change. If the runner avoids running and misses out on an activity that they would otherwise do, it’s counted as an indirect, or counterfactual, cost of climate change. Calculating both the costs of climate change and the costs of policies allows researchers to evaluate the effectiveness of policies addressing climate change, he said.

Photo: Amanda Giang.

Kishimoto also discussed how different types of policies aimed at reducing greenhouse gas emissions work, including measures like carbon taxes and trading plans, regulations, and policies encouraging research and development of new technology.

Climate science measurements

Daniel Gilford and Jareth Holt, graduate students in the Department of Earth, Atmospheric and Planetary Sciences, led a session on January 29 on how climate scientists measure climate change.

Gilford started the class out by explaining the concept of radiative forcing, which is a measure of the net difference between the energy the Earth and atmosphere absorbs from sunlight, and the energy released back into space after a change in the atmospheric composition (such as increasing CO₂). A change that traps more heat in the Earth system is a positive radiative forcing and contributes to warming. The primary gas causing increased radiative forcing is CO₂, but other gases like methane, nitrous oxide, and ozone also play a role.

Jareth Holt discussed how climate models account for factors that affect radiative forcing. To do this, models have become more complex, Holt said. For example, in the 1990s, climate models underestimated the importance of aerosols in calculating radiative forcing, and had simple representations. Models now have more detailed representations of how aerosols behave in the atmosphere.

On the other hand, there are reasons why researchers might want to simplify models. Modern climate models use supercomputers, he explained, and can take weeks or even months to make one simulation. Simpler models run more quickly, and allow researchers to complete a larger number of simulations, helping to understand the uncertainty in the climate system. As a result, climate modeling requires constant balancing between complexity and computational efficiency.

Climate fundamentals

Daniel Gilford and Jareth Holt led a session on January 26 covering basic climate science, and the history of the discipline. Climate science, Holt said, is the study of variability, patterns, and statistics over time.

	Photo: Daniel Gilford.

The field can trace its roots back to the 1820s, when Joseph Fourier discovered that the Earth’s atmosphere traps heat. The modern study of climate change got its start in the 1890s when Svante Arrhenius built the first simple model balancing energy in the Earth system. He determined that adding CO₂ to the atmosphere traps energy, causing warming, which is a principle still used by climate scientists today.

Gilford and Holt also explained what makes a gas a greenhouse gas. The Earth’s atmosphere is made of mostly nitrogen and oxygen, but those gases absorb almost none of the energy given off by the Earth’s surface. Instead, small amounts of other gases, like water vapor and CO₂, trap the most energy. Other gases like methane and nitrous oxide are present in even smaller amounts, but because they strongly absorb energy at different wavelengths than CO₂ and water vapor, they can also contribute dramatically to warming.

For the full list of 2015 Global Change IAP Clasess click here.