Models
and molecules: Interactive chemistry comes of age
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Don Wuebbles |
Analyzing which chemicals matter most to climate—and how much
difference each one makes—is the forte of Donald Wuebbles. Director
of the University of Illinois’ School of Earth, Society and Environment,
Wuebbles is also part of the team working to bring more realistic chemical
interactions into the NCAR-based Community Climate System Model (CCSM).
At Lawrence Livermore National Laboratory in the 1980s, Wuebbles devised
the concept of ozone depletion potentials. This index shows the relative
power packed by each type of ozone-threatening molecule. Wuebbles helped
transmute the concept into global warming potentials, a key tool for
policymakers. The new index is based on the heat-absorbing ability
and lifespan of each greenhouse gas. Methane is far more powerful than
carbon dioxide, for example, but it stays in the atmosphere for much
less time. (There’s also much less of it.)
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The chemistry-oriented version
of the Community Climate System Model can track a variety of
constituents and their interactions with the atmosphere.
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“I’m intrigued, as are a lot of other people, in looking
at how global change interacts with atmospheric chemistry and biogeochemical
cycles,” says Wuebbles. He and colleagues at Livermore built
a pioneering three-dimensional model of air chemistry in the early
1990s. “We were doing well, but when I came to Illinois I said,
I’m not going to develop another model. These are expensive tools,
and they take a lot of time.”
Instead, Wuebbles took advantage of NCAR’s community-based model
development. He began working with NCAR lead Guy Brasseur on MOZART
(Model for Ozone and Related Chemical Tracers). The model soon became
a flagship tool for analyzing more than 100 airborne compounds. However,
it wasn’t designed to show the two-way interaction between chemicals
and climate change.
That’s now changing. In an effort led by NCAR’s Peter Hess,
MOZART is now being incorporated into the CCSM in a fully interactive
fashion. The upgraded model will depict salt, dust, soot, and a wide
range of other particles and gases that influence cloud formation and
radiation. Tests began in 2007 on this chemistry component of CCSM. “I
think we’re going forth with a version that has all the right
stuff,” says Wuebbles. “There could be some interesting
surprises.”
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