Daniel Jacob, associate professor of atmospheric chemistry, accepted a tenured position in the Division of Applied Sciences and the Department of Earth and Planetary Sciences earlier this month.

The 36-year-old Jacob has won several major awards for his work on the affects of human activity on the lower atmosphere. He has also garnered high ratings from the undergraduates he has taught in his decade at Harvard.

"I'm very excited about it," Jacob said in an interview yesterday. "I came to Harvard because I thought the best work in the world was being done here and I plan to stay a very long time."

Jacob has focused his work on how urban and regional air pollution have affected global environmental problems. He says he has found that pollution may have positive effects.

"Smog is obviously a very bad thing when you look at it from the urban point of view in the eastern United States," he says. "But it may actually work to clean the atmosphere."

Similarly, he says that efforts to lessen sulfur dioxide emissions in order to reduce acid rain could have a negative effect, by cutting down the number of particles in the atmosphere. This would mean that less sunlight is reflected back into space, increasing global warming.

Jacob's work is unusual because he requires large computing resources to simulate his environmental models. He says he sometimes must design faster computer systems in order to do his work.

Jacob also spends time on field expeditions, studying the environment first-hand.

The francophone says he is currently organizing an expedition over the south Pacific to study what he says is "probably the cleanest place in the world, a place where no one has been."

Jacob and fellow researches will use a DC 8 aircraft to study the atmosphere of the region between Easter Island, Fiji, Tahiti, and New Zealand.

Last year Jacob won an award from the American Geophysical Union as the best scientist younger than 35.

Rotch Professor of Atmospheric Science Michael B. McElroy, who taught Science A-30: "The Atmosphere" with Jacob for four years, says that Jacob is a "phenomenal" teacher.

"It's a sobering experience, teaching a course with him," McElroy said yesterday.

McElroy, who was on the search committee that selected Jacob, said that Jacob is "the best young scientist in the world in what he works in."

"Harvard is very fortunate to have persuaded him to stay here," McElroy said