Benefits from Reducing Short-lived Climate Forcers

A variety of measures that improve human welfare through better local air quality will also result in near-term climate benefits

In recent years, MAG’s work has demonstrated that controlling long-lived greenhouse gases (GHGs) has significant near-term co-benefits for controlling air pollution at the local scale, including cutting air pollution control costs. However, there is a problem, namely, that if air pollution control measures are seen only as ancillary benefits, they can seem less relevant in societies where climate change mitigation ranks low on the policy agenda.

One way of countering this perception is to focus on air quality measures that, as a side effect, also reduce climate change. As most air pollutants also act as climate forcers, although at a shorter time scale than long-lived greenhouse gases such as CO2 and N2O, tackling these short-lived climate forcers—especially black carbon (soot), tropospheric ozone, and methane—could lead to a lower rate of temperature increase in the near term, slowing Arctic ice thaw, avoiding irreversible damage to sensitive ecosystems, and avoiding changes in rainfall patterns.

A systems approach

To explore potential approaches to maximizing the co-benefits af air pollution control for climate change, MAG has extended its GAINS (Greenhouse gas—Air pollution interactions and
synergies) model to include all the components necessary for comprehensive global assessment of the sources, mitigation potentials, and effects of the short-lived climate forcers.

GAINS, which now distinguishes 120 regions covering the entire world, includes emission inventories for black carbon, organic carbon, and carbon monoxide, in addition to the inventories of the six Kyoto gases and five air pollutants. This enables assessment not only of the mitigation potentials and costs for these substances but also of the benefits of mitigation for human health, the Earth's vegetation, and climate change.

Sixteen measures that improve human welfare and simultaneously limit temperature
increase

In 2011 MAG used the updated GAINS model to explore practical means for improving human welfare while simultaneously limiting temperature increases, especially in the near-term. Of the more than 2,000 mitigation options considered in GAINS for improving air quality, the research team identified 16 readily available measures that, together, could reduce the global
warming potential of short-lived pollutants by up to 60 percent compared to a baseline projection. These options include technical measures aimed at reducing methane and black carbon emissions, such as the extended recovery of coal mine gas, the wide-scale introduction of pellet stoves and boilers in the industrial sector, replacing traditional coke ovens with modern recovery ovens, and installing particle filters on diesel engines.

Measures with a strong regulatory context included the replacement of traditional biomass cook stoves in developing countries with clean and modern fuel stoves, a ban on the open burning of agricultural waste, and enforcing existing legislation to eliminate high-emitting diesel vehicles.

MAG contributed these new findings to the comprehensive scientific assessment of "Measures to Limit Near-Term Climate Change and Improve Air Quality” (UNEP/WMO, 2011) (http://
www.unep.org/dewa/Portals/67/pdf/BlackCarbon_report.pdf) organized by the United Nations Environment Program (UNEP) together with the World Meteorological Organization (WMO).

The impacts of these 16 measures on temperature were explored using the climate modeling tools of NASA and ECHAM. It was found that full implementation of these measures could slow the rate of temperature increase by 0.54 ± 0.05°C in the coming decades (see graph), and help keep warming 2°C below the preindustrial level in the near-term. This would provide enhanced warming mitigation potential in the Arctic and the Himalayas and reduce regional disruptions to traditional rainfall patterns.

Most relevant for local policy agendas, however, these measures would also increase human wellbeing through reduced local air pollution, improve local environmental quality, increase
security of food and energy supply, and reduce water demand. In many cases, these measures would also result in more efficient energy use and thus also reduce emissions of long-lived greenhouse gases.

Results were published in Science (Shindell et al., 2012).


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Last edited: 22 July 2013

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Markus Amann

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Air Quality and Greenhouse Gases

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Air Quality and Greenhouse Gases

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