Balancing the Climate Budget
Confronting Climate Change
We see the signs everywhere—our planet’s future is in jeopardy. As global temperatures rise, greenhouse gases reach record levels and extreme weather events strike more frequently, we must ask the question: What will it take to solve the grand challenge of climate change?
Researchers in the University of Maryland’s College of Computer, Mathematical, and Natural Sciences (CMNS) are fiercely committed to the fight against global warming. These scientists are tapping into satellite data to predict crop-killing droughts before they happen, identifying trees that adapt to climate change instead of worsening it, and unraveling the complex relationship between airborne pollutants and weather conditions. Grand challenges demand bold ideas and real-world solutions. In CMNS, we lead Fearlessly Forward.
Trying to predict, combat and prepare for climate change is a bit like managing the budget of a major multinational corporation. But instead of knowing where all the money goes, you have to know where all the energy goes. How much sunlight hits the planet?
How much of it heats the ground and ocean versus how much is absorbed or reflected by gases and water vapor in the atmosphere? And how does the concentration of those gases—particularly greenhouse gases like carbon dioxide—change over time due to human activities and natural processes?
These are huge and complex accounting questions that Distinguished University Professor Zhanqing Li has been helping to answer for decades. In the mid-1990s, Li discovered that aerosols—tiny airborne particles—in clouds played a major role in trapping and reflecting heat. His work redefined how scientists view the role of clouds in Earth’s climate, and his model is used today by NASA as part of the foundation for calculating the global energy budget.
Now, the professor in the Department of Atmospheric and Oceanic Science and the Earth System Science Interdisciplinary Center focuses on understanding the interaction between clouds, pollution and climate.
“Cloud variation is still the most difficult issue for understanding the energy budget and making climate predictions,” Li said. “It is a very complex and interesting story. Aerosols from pollution change the microphysics of clouds to influence how much energy they trap or radiate to space and how they hold water and produce rain. This can hide the total effects of greenhouse gases.”
Li’s research, for example, showed that aerosol pollution from sources like factories, cars and fossil fuel-based power plants has a significant cooling effect on global climate. It’s not as much as the warming effect of greenhouse gases that come from the same sources, but when scientists calculate the benefits of reducing emissions from those sources, the cooling effect of aerosols is an important budget item that has to be factored in.
“These dynamics are very important to understand because as countries work to reduce greenhouse gases and pollution, there will be changes due to a reduction in aerosols that they need to understand and prepare for,” he said.
The interaction between aerosols and clouds also has important local effects. In highly polluted areas in China, Li found that clouds need to be much thicker to produce rain, and when they do, they tend to produce more thunderstorms and fewer drizzles. But aerosols complicate the picture, because in lower concentrations, some aerosols suppress thunderstorms and increase the number of light rains.
That means the types of aerosols pumped into the air could tamp down or ramp up local thunderstorms, which increase floods in urban areas and harm crops. By identifying these complicated interactions, Li provides critical information policymakers need to prepare their communities for future weather conditions as they try to clean their air of pollution and greenhouse gases.
Written by Kimbra Cutlip
This article was published in the Summer 2022 issue of Odyssey magazine. To read other stories from that issue, please visit go.umd.edu/odyssey.
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