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newsrel -- California’s efforts to clean up diesel engines have helped reduce impact of climate change on state, study finds

Posted: 13 Jun 2013 09:52:42
Please consider the following news release from the California
Air Resources Board:




News Release 13-32

June 13, 2013

Melanie Turner
(916) 322-2990

California’s efforts to clean up diesel engines have helped
reduce impact of climate change on state, study finds

Clean diesel programs slashed black carbon, a powerful short-term
contributor to global warming

SACRAMENTO - Reductions in emissions of black carbon since the
late 1980s, mostly from diesel engines as a result of air quality
programs, have resulted in a measurable reduction of
concentrations of global warming pollutants in the atmosphere,
according to a first-of-its-kind study examining the impact of
black carbon on California’s climate.
The study, funded by the California Air Resources Board and led
by Dr. Veerabhadran Ramanathan of the Scripps Institution of
Oceanography at the University of California, San Diego,
estimates that reductions in black carbon as a result of clean
air regulations were equivalent to reducing carbon dioxide
emissions in California by 21 million metric tons annually or
taking more than 4 million cars off California roads every year.

“We know that California’s programs to reduce emissions from
diesel engines have helped clean up the air and protect public
health,” said ARB chairman Mary D. Nichols. “This report makes it
clear that our efforts to clean up the trucks and buses on our
roads and highways also help us in the fight against climate
Black carbon — tiny soot particles released into the atmosphere
by burning fuels — has been linked to adverse health and
environmental impacts through decades of scientific research. It
is also one of the major short-lived contributors to climate
change. The major sources of black carbon in California are
diesel-burning mobile sources, residential wood burning in
fireplaces and heaters, agricultural burning and wildfires.

The 3-year-study, titled “Black Carbon and Regional Climate of
California,” was conducted by UC San Diego and the U.S.
Department of Energy’s Lawrence Berkeley National Laboratory and
Pacific Northwest National Laboratory. It is the first
comprehensive regional assessment of the climate impact of black
carbon on California. In conducting the study, scientists used
computer models and air pollution data collected by aircraft,
satellite and ground monitors.

The study’s results support a growing body of scientific evidence
that suggests it is possible to immediately slow the pace of
climate change regionally by reducing emissions of short-lived
climate pollutants, like black carbon.

According to co-author Dr. Tom Kirchstetter of LBNL, black carbon
levels have decreased by about 90 percent over a 45-year period,
beginning with the establishment of CARB in 1967, mostly as a
result of state regulations for diesel engine emissions.
Researchers found the state’s efforts to reduce diesel emissions
to have lessened the impact of global warming on California,
supporting earlier theoretical computer modeling by Dr. Mark
Jacobson of Stanford University that reducing black carbon from
diesel combustion is a potent ‘climate cooler.’
The reductions occurred during a time when diesel fuel
consumption increased by about a factor of five, attesting to the
effectiveness of CARB regulations requiring cleaner fuels and
vehicle technology.

The study took a conservative approach in examining the impact
black carbon has on the Golden State. Researchers considered
emissions only from diesel-powered trucks and buses, and off-road
diesel equipment and vehicles to estimate the equivalent
reduction of carbon dioxide.
When all sources of black carbon emissions from diesel fuel
combustion are considered, including farming and construction
equipment, trains and ships, the reduction in carbon dioxide
emissions can be as high as 50 million metric tons per year over
the past 20 years. That’s roughly equal to a 13-percent reduction
in the total annual carbon dioxide emissions in California.

As ARB’s current efforts to clean up trucks and buses move
forward, resulting in the continued cleanup and turnover of older
heavy-duty diesel vehicles, California should continue to see
declines in particulate matter emissions. Advanced engine
emissions control systems and filters are expected to
dramatically reduce emissions from all new diesel engines.
Current diesel truck engines, for example, are over 90 percent
cleaner than models from years when they were unregulated.
“If California’s efforts in reducing black carbon can be
replicated globally, we can slow down global warming in the
coming decades by about 15 percent, in addition to protecting
people’s lives,” Ramanathan said. “It is a win-win solution if we
also mitigate carbon dioxide emissions simultaneously.”

Black carbon has the effect of warming the atmosphere because it
is effective at absorbing sunlight. However, it is emitted
together with a range of other particle pollutants, including
organic carbon, sulfur and other chemicals, some of which have a
cooling effect, typically by reflecting sunlight. Reducing diesel
emissions can therefore lead to a reduction of both warming and
cooling particles. The report, however, is the first to confirm,
based on both observations and computer modeling, that the
warming effect of black carbon dominates, overwhelming any
cooling effect of other pollutants. This confirms the positive
impact reducing diesel emissions has on fighting climate change.
Other findings include:

• The study found evidence to link brown carbon — a form of
organic carbon aerosols — to warming. Therefore, a commonly held
view that organic particles from wildfires primarily reflect
sunlight, and cause cooling, was not supported by the study.

• A finding that black carbon particles increased the number of
drops of water in clouds, while decreasing the size of those
drops, a condition that can reduce or delay rain.

Editor’s note: A copy of the report can be found here:

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