Black carbon, ozone report stirs climate negotiations

But UNEP makes it clear that it only offers co-benefits in short-range to reduce them, cannot replace CO₂ cuts

By Aditya Ghosh

Bonn, June 14: The politically sensitive issue of black carbon sneaked in the climate negotiations following a report by the United Nations Environment Programme (UNEP) and World Meteorological Organisation (WMO) that was released here in Bonn on Tuesday. The findings of the study indicated that controlling black carbon from soot and smog would help significantly to arrest global temperature increase in wake of increasing green house gases in the atmosphere.

However, it also made it very clear that black carbon in isolation will never be able to solve warming of the globe and can only have a positive impact on temperature increase if applied in conjunction with measures of mitigating CO₂ emissions. “They have to be complementary processes to yield the benefits and not run in isolation,” said Johan Kuylenstierna, director of Stockholm Environment Institute and lead author of the study.

“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.” 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 by mid-century, the study said.

It also would avoid 2.5 million premature deaths every year from air pollution and would raise crop production by 50 million tons annually, said Kuylenstierna.

But politics crept in while discussion on methodological issues at an AWG-KP contact group meeting, the facilitator of concerned spin-off group said that there was serious differences on which new gases of shorter life span be included in the basket of GHGs that needed to be controlled.

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.

On current trajectories, temperatures are set to go up 1.30C, on top of the 0.90C jump since human-induced warming kicked in, by 2050 bringing the total compared to preindustrial levels to 2.20C.

But quickly tackling black carbon and smog-related ozone could slash 0.50C off the temperature increase projected for 2030, putting the two-degree target back on track, the new findings suggest.

The Gothenburg protocol, which sets emission ceilings for 2010 for four pollutants sulphur, NOx, VOCs and ammonia, might include ground ozone and black carbon but it remained a ‘tricky issue’ politically claimed Martin Williams, Chair of the Executive Body, UNECE Air Convention.

Ground-level, or tropospheric, ozone -- a major ingredient of urban smog -- is both a powerful greenhouse gas and a noxious air pollutant. It is formed from other gases including methane, itself a potent driver of global warming.

A threefold increase in concentrations in the northern hemisphere over the last century has made it the third most important greenhouse gas. Unlike carbon dioxide, which lingers in the atmosphere for centuries once emitted, black carbon and ozone disappear quickly when emissions taper off.

Surya Sethi, a former climate negotiator from India said that benefits were regional in nature and policy interventions depended on the issues such as cost benefits, design aspects and cultural practices. “It can offer only temporary reprieve from the problem of climate change,” he said. The greater benefits would be domestic policy concerns, he said, that would include health, water, regional monsoon variability. But the financial and institutional barriers must be addressed with global assistance,” he said.