Air Quality and Climate Change: A Delicate Balance
Air Quality and Climate Change: A Delicate Balance
Reducing emissions of climate pollutants to slow the pace of climate change is expected to have ancillary benefits in terms of improving air quality. In May 2015 the Climate and Clean Air Coalition (CCAC) agreed on the framework for a strategic five-year plan to maximize climate mitigation/air quality co-benefits. The CCAC is an initiative of six governments and the United Nations Environment Programme that promotes concrete, practical options for reducing short-lived climate pollutants such as methane and black carbon. The strategic framework will be formally presented at the Paris climate conference in December.
But mitigating the adverse effects of air pollution is as complex as the chemistry that produces these agents. For instance, one common air pollutant, sulfur dioxide (SO2), complicates efforts to simultaneously control both global warming and air quality. Power plants, vehicles, and other sources emit SO2 that forms sulfate particles, which harm human health but also effectively block solar radiation from reaching the surface—a cooling effect. China is seeking to reduce its SO2 emissions in hopes of improving urban air quality. But large reductions in SO2 emissions could result in enhanced global warming, Melamed says.
A sulfate particle in the air, though, would not be separate and distinct from other types of particles, and ways in which pollutants combine themselves influence how they affect climate. "You can have a particle of black carbon with a surface covering of sulfate, a pollutant that enhances cooling of the atmosphere. Or you can have a particle of sulfate with a covering of black carbon, a pollutant that increases warming," Melamed explains. "The mixture of pollutants really matters [with respect to] how they affect climate."
On 31 March 2015 the United States stated its intention to reduce its greenhouse gas emissions by 26–28% below 2005 levels within the next 10 years. This pledge, and those of several other nations, will be a basis for negotiations at the Paris conference, where parties aim to finally adopt a binding global agreement on measures to limit global temperature increase to below 2°C. The final negotiated agreement is proposed to come into effect in 2020.
The United States has already made steps toward leveling off its greenhouse gas emissions. Despite a 2% increase from 2012 to 2013, U.S. emissions decreased by 9% overall between 2005 and 2013. Continuing these cuts will also reduce concentrations of O3 and many types of PM in the atmosphere, with substantial public health benefits, says Aaron Bernstein, associate director of the Center for Health and the Global Environment at Harvard T.H. Chan School of Public Health. "If we do what we need to do to deal with climate change," Bernstein says, "we will be healthier."
Managing Air Pollution and Climate Change at the Same Time
Reducing emissions of climate pollutants to slow the pace of climate change is expected to have ancillary benefits in terms of improving air quality. In May 2015 the Climate and Clean Air Coalition (CCAC) agreed on the framework for a strategic five-year plan to maximize climate mitigation/air quality co-benefits. The CCAC is an initiative of six governments and the United Nations Environment Programme that promotes concrete, practical options for reducing short-lived climate pollutants such as methane and black carbon. The strategic framework will be formally presented at the Paris climate conference in December.
But mitigating the adverse effects of air pollution is as complex as the chemistry that produces these agents. For instance, one common air pollutant, sulfur dioxide (SO2), complicates efforts to simultaneously control both global warming and air quality. Power plants, vehicles, and other sources emit SO2 that forms sulfate particles, which harm human health but also effectively block solar radiation from reaching the surface—a cooling effect. China is seeking to reduce its SO2 emissions in hopes of improving urban air quality. But large reductions in SO2 emissions could result in enhanced global warming, Melamed says.
A sulfate particle in the air, though, would not be separate and distinct from other types of particles, and ways in which pollutants combine themselves influence how they affect climate. "You can have a particle of black carbon with a surface covering of sulfate, a pollutant that enhances cooling of the atmosphere. Or you can have a particle of sulfate with a covering of black carbon, a pollutant that increases warming," Melamed explains. "The mixture of pollutants really matters [with respect to] how they affect climate."
On 31 March 2015 the United States stated its intention to reduce its greenhouse gas emissions by 26–28% below 2005 levels within the next 10 years. This pledge, and those of several other nations, will be a basis for negotiations at the Paris conference, where parties aim to finally adopt a binding global agreement on measures to limit global temperature increase to below 2°C. The final negotiated agreement is proposed to come into effect in 2020.
The United States has already made steps toward leveling off its greenhouse gas emissions. Despite a 2% increase from 2012 to 2013, U.S. emissions decreased by 9% overall between 2005 and 2013. Continuing these cuts will also reduce concentrations of O3 and many types of PM in the atmosphere, with substantial public health benefits, says Aaron Bernstein, associate director of the Center for Health and the Global Environment at Harvard T.H. Chan School of Public Health. "If we do what we need to do to deal with climate change," Bernstein says, "we will be healthier."
