13 January 2012
The research, led by Drew Shindell of NASA's Goddard Institute for Space Studies (GISS), finds that focusing on these measures could slow global mean warming 0.5ºC (0.9 ºF) by 2050, prevent between 0.7 and 4.7 million premature deaths each year and increase global crop yields by up to 135 million tons per season. While all regions of the world would benefit, countries in Asia and the Middle East would see the biggest health and agricultural gains from emissions reductions.
The team of experts from around the world considered about 400 control measures based on existing, proven technology, whose effects are included in the International Institute for Applied Systems Analysis (IIASA) GAINS model, but focused their analysis on 14 measures that, according to the GAINS model, would have the greatest climate benefit. All 14 would curb the release of either black carbon or methane, pollutants that harm human or plant health while simultaneously exacerbating climate change.
"We've shown that implementing specific practical emissions reductions chosen to maximize climate benefits would also have important 'win-win' benefits for human health and agriculture," said Shindell.
Black carbon, a product of burning fossil fuels or biomass such as wood or dung, can worsen a number of respiratory and cardiovascular diseases. The small particles also absorb radiation from the sun causing the atmosphere to warm and rainfall patterns to shift. In addition, they darken bright land surfaces, such as ice and snow, reducing their reflectivity and hastening global warming.
Methane, a colorless and flammable substance that’s a major constituent of natural gas, is both a potent greenhouse gas and an important precursor to ground-level ozone. Ozone, a key component of smog and also a greenhouse gas, damages both crops and human health.
The team concluded that control measures would deliver Tajikistan, Kyrgyzstan and Russia – countries with large areas of snow or ice cover - the greatest protection against global warming, while the south Asian countries of Bangladesh, Nepal, and India would see the biggest reductions in premature deaths. Iran, Pakistan and Jordan would experience the most improvement in agricultural production. And southern Asia and the Sahel region of Africa would see the most beneficial changes to precipitation patterns.
Black carbon and methane have many sources and reducing emissions would require that societies make multiple infrastructure upgrades. For methane, the key strategies the scientists considered were capturing gas that would otherwise escape from coal mines and oil and natural gas facilities, reducing leakage from long-distance pipelines, preventing emissions from city landfills, updating wastewater treatment plants, aerating rice paddies more, and limiting emissions from manure on farms.
For black carbon, the strategies analyzed include installing filters in diesel vehicles, keeping high-emitting vehicles off the road, upgrading cook stoves and boilers to cleaner burning types, installing more efficient kilns for brick production, upgrading coke ovens, and banning agricultural burning.
The scientists used computer models developed at GISS and the Max Planck Institute for Meteorology in Hamburg, Germany, to model the impact of emissions reductions. The modeling showed widespread benefits from the methane reduction because methane is evenly distributed throughout the atmosphere.
In contrast, benefits from reducing black carbon, which falls out of the atmosphere after a few days, were stronger in certain regions than others. The effect of reducing black carbon, for example, would be particularly strong in areas with large amounts of snow and ice. In the Himalayas and the Arctic, such reductions would reduce projected warming over the next three decades by up to two-thirds.
"Protecting public health and food supplies may take precedence over avoiding climate change in most countries, but knowing that these measures also mitigate climate change may help motivate policies to put them into practice," Shindell said.
While carbon dioxide is the primary driver of global warming over the long-term, limiting black carbon and methane are complementary actions that would have a more immediate impact because these two pollutants circulate out of the atmosphere more quickly.
"The scientific case for fast action on these so-called 'short-lived climate forcers' has been steadily built over more than a decade, and this study provides further focused and compelling analysis of the likely benefits at the national and regional level,” said United Nations Environment Program (UNEP) Executive Director Achim Steiner.
The study has been carried out by an international team, including scientists from NASA's Goddard Institute for Space Studies, the Stockholm Environment Institute, the International Institute for Applied Systems Analysis, Austria, the Joint Research Centre, European Commission, Italy, Scripps Institution of Oceanography, USA, Argonne National Laboratory, USA, King’s College London, and the UK Centre for Ecology and Hydrology.
To see interactive and embeddable country-by-country graphs and maps of the impact of emissions reductions, please visit the NASA website
The research was a key input to the recently published UNEP/WMO Integrated Assessment of Black Carbon and Tropospheric Ozone report available at: http://www.unep.org/dewa/Portals/67/pdf/BlackCarbon_report.pdf
The new study builds on a UNEP/World Meteorological Organization report, involving IIASA published in 2011: http://www.iiasa.ac.at/docs/HOTP/2011/Nov11/UNEP.pdf
Last edited: 19 July 2013
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