AMSTERDAM (AP) — The struggle to contain climate change usually focuses on
reducing carbon dioxide. But black carbon and ozone, the main ingredients of
soot and smog, also add to global warming, and controlling them will act
quickly to slow rising temperatures, a U.N. agency said Tuesday.
Black carbon comes from solid particles from tailpipes, forest fires or
wood-burning stoves and brick kilns commonly found in poor countries. It
absorbs sunlight, and is most damaging when it settles on the Arctic snow or
mountain glaciers, causing ice packs to melt more rapidly.
Another climate changer is ground-level ozone, said the U.N. Environment
Program. Ozone, which is largely formed from methane, is beneficial as a
high-altitude blanket around the Earth, but at 10 to 15 kilometers (6-9
miles) above the surface it acts as a powerful greenhouse gas and a
contributor to urban smog.
A study released at U.N. climate negotiations in Bonn, Germany, by UNEP and
the World Meteorological Organization said big cuts in black carbon and
ozone-forming methane not only would slow global warming but would curb
respiratory diseases and reduce damage to crops.
Carbon dioxide, or CO2, mainly from burning fossil fuels by heavy industry
and transportation, accumulates for centuries in the atmosphere, and has a
long-term impact on global warming. Black carbon, methane and ozone are
“short-lived climate forcers,” and reducing them has a more immediate
effect, the UNEP report said.
“We have not found a silver bullet,” said UNEP’s chief scientist Joseph
Alcamo. “What we have found is a strategy for a very powerful compliment to
needed CO2 reduction.”
Johan Kuylenstierna of the Stockholm Environment Institute, the report’s
chief author, said taking steps to cut black carbon and ground-level ozone
over the next 20 years would “significantly slow” anticipated global
warming, making a difference of 0.5 degree Celsius (0.9 F) by mid-century.
It also would avoid 2.5 million premature deaths every year from air
pollution and would raise crop production by 50 million tons annually, he
The report listed a 16 actions that should be taken.
Black carbon can be reduced with filters on diesel engines, taking old
vehicles off the roads and replacing wood-fired cooking stoves and brick
kilns with biomass fuels.
Ozone-building methane emissions can be slashed by recovering leaks from
ventilation shafts in coal mines, gas facilities and pipelines, by
separating and treating biodegradable garbage from municipal waste, and
changing the diet of methane-emitting livestock.
Adopting such measures quickly would enhance the prospects of limiting the
rise in global temperatures to 2 degrees Celsius (3.6 F) above preindustrial
levels, the target set by international negotiators. One result would be a
reduction in the projected warming of the Arctic over the next 30 by about
two-thirds, it said.
“These are not measures that we have to invent. They already exist,”
Kuylenstierna told reporters in Bonn. But they must be implemented on a wide
scale across the globe.
The long-term answer to climate change remains a sharp reduction of carbon
dioxide, the most common and long-lasting greenhouse gas, he said.
that a global average temperature increase of more than 2 degrees raises the
risk of disastrous climate changes effecting agriculture, sea levels and the
survival of species.