News Story

November 15, 2011

Profile: Daniel Jacob

As the eldest son of a third-generation scientist, Daniel Jacob initially studied science because it was what was expected of him. It wasn’t until he began his graduate studies that it became an obsession rather than an obligation.

“I was going through the motions,” says Jacob, McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering, of his early science education in France. Then, when he arrived at the California Institute of Technology for graduate studies in engineering, there was “a spark.” “I think it was the view of science as puzzles to solve. This—combined with the freewheeling attitude you have in the U.S.—it was like a breath of fresh air.”

Jacob first became interested in atmospheric chemistry after reading a 1978 Scientific American article on acid rain. Indeed, when he entered the field in the early 1980s, there was a heavy focus on the topic—an especially relevant subject in nearby Los Angeles at the time. But after being persuaded to join the Harvard faculty by Butler professor of environmental studies Michael McElroy in 1985, Jacob wanted to expand the reach of his work beyond local pollution issues, and began to concentrate his studies on the chemistry of the global troposphere—the lowest of Earth’s atmospheric layers.

His global atmosphere analysis has increasingly led Jacob to the Arctic, a region in the midst of radical changes. “The warming we are seeing there right now is much faster than has been predicted by any of the climate models,” says Jacob. He’s worked with NASA on several Arctic research projects, using satellites and planes to collect data on the chemistry of the region’s atmosphere. One of the agents that could be accelerating the Arctic warming, he says, is soot given off by dirty combustion—everything from diesel engines to forest fires. When these black soot particles land in the Arctic, they can coat the snow and instead of reflecting the sunlight, absorb the sun’s heat.

One of the many negative effects of higher Arctic temperatures, says Jacob, is the release of mercury into the ocean. The sea ice in the Arctic is a frequent destination for atmospheric mercury emissions from things like coal burning and waste incineration. He has been fascinated by the element of late, and is working to better understand the chemistry at work in its continuous cycle: from atmospheric emissions, to deposition on the ice, to the ocean, and then back into the atmosphere. “[The melting of the sea ice] is going to have a very big effect on the accumulation of mercury in fish,” says Jacob. “And that’s of particular concern to indigenous populations who depend on fish for sustenance.”

All of this research has found its way into “Atmospheric Chemistry”, a course Jacob has taught for more than two decades. Instructing young scientists has provided a kind of constant, allowing him a unique perspective on the field’s growth. “I always tell my students that the things that we are teaching them now were not even known ten or twenty years ago,” he says. “And today, they get to see the science as it develops.”

By: Dan Morrell

Note: This article originally appeared in Environment@Harvard Volume 3, Issue 2

Research Areas: 

Harvard University
Center for the Environment

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