temporarily cut the city’s black carbon
emissions by about 25 percent.
New research, however, suggests that
the climate benefits of cutting black car-
bon might come with a flip side. In May
in Geophysical Research Letters, a team
led by Wei-Ting Chen of the Jet Pro-
pulsion Laboratory in Pasadena, Calif.,
modeled the climatic outcome of slash-
ing black carbon emissions in half. The
cooling benefits of reducing emissions,
her team found, were partially offset by
the fact that less soot meant fewer cloud
condensation nuclei and thus fewer
clouds to cool things down. Still, says
team member John Seinfeld of Caltech,
“on the whole, black carbon reduction
is still good for climate, and good for
human health as well.”
Targeting particular sources of black
carbon might be important in reducing
it efficiently. Aerosol plumes dominated
by black carbon from fossil fuel burning
in China were roughly twice as efficient
at absorbing solar radiation and heating
things up as were black carbon plumes
from biomass burning, Veerabhadran
Ramanathan, a black carbon specialist
at the Scripps Institution of Oceanog-
raphy in La Jolla, Calif., and colleagues
reported in August in Nature Geoscience.
With other scientists, Ramanathan
has launched Project Surya, which aims
to replace polluting cookstoves across
India with low-cost, cleaner alternatives.
Women who receive the new stoves are
required to remove and photograph the
filter that strips out black carbon particles. “Just seeing the black filter makes
them say, ‘Is this what we are breathing?’” says Ramanathan.
Getting local
Even as researchers push into unexplored territory in aerosols, others are
looking to cover some ground closer
to home — understanding how climate
change will affect people’s lives. In this
case, scientists aim to improve their predictions of the regional impacts of climate
change. Many local effects are already
apparent. A major U.S. government
report last year, for instance, detailed
how climate change has led to heavier
Regional forecasts
a global climate model from the last iPcc
report (top) doesn’t include enough detail on
factors such as elevation to get at local
effects. While the iPcc model predicts april
snow cover for only a small area in canada, a
regional model (bottom) predicts depths of up
to 3 meters in some U.s. locales. soUrce: Ncar
Elevation in meters
Snow depth in meters
0.1 0.2 0.4 0.6 0.8 1.0 1. 5 2.0 2. 5 3.0 4.0
winter rain in the Northeast, more intense
hurricanes in the Southeast and smaller
snowpacks in the Rocky Mountains.
Global temperatures are projected
to increase by 2 to 4 degrees Celsius
by the end of this century, but locally
the effects could be much stronger. For
instance, computer models that incor-
porated a global temperature rise of
2 degrees Celsius found that large parts
of Europe, North America and Asia
could experience heat waves with tem-
peratures up to 6 degrees Celsius higher
than normal. Local factors such as plant
root depth and forest cover could partly
account for the differences, Robin Clark
and colleagues at the Met Office Hadley
Centre in Exeter, England, wrote in Sep-
tember in Geophysical Research Letters.
