Soot and Smog Important in Climate Change Fight, Says UN

As countries around the world work to fight climate change, policymakers could buy time by reducing emissions of soot and compounds which contribute to ground-level ozone. That’s the message of a UN study released on Friday, which says curbing soot and ozone pollution could reduce future global warming by 0.9 degrees Fahrenheit. The news is particularly important because while a long-term phase-out of the sources of carbon dioxide emissions could take years to implement, reductions in soot and ground-level ozone could be achieved relatively quickly.

For many people the word “soot” may conjure up images of nineteenth-century villages cloaked in a dusting of black coal ash. However soot is not a thing of the past, and today massive amounts are still produced from the incomplete combustion of coal and wood burned for fuel. Ground level ozone, also known as smog, results from chemical reactions that occur in the atmosphere when compounds like sulfur dioxide and carbon monoxide are released by burning fossil fuels.

Steps that could significantly reduce soot and smog in the include reducing the practice of natural gas “flaring,” deploying cleaner-burning stoves in developing countries, and quickly closing the oldest and dirtiest coal plants which still emit large amounts of soot and sulfur dioxide.

Since the burning of fossil fuels and wood is the most important source of soot and smog pollution, steps that were already essential for reducing carbon emissions may prove even more important than we thought. When it comes to the climate change impacts of coal plants, vehicles, and activities that cause deforestation, scientists and policymakers have so far focused mainly on emissions of carbon dioxide. Yet coal-fired power plants, internal combustion engines, and deforestation are all major contributors to soot and smog generation as well. In moving to a clean economy, world nations can curb multiple greenhouse gases at once.

At the same time reducing soot and smog has more immediate benefits than cutting carbon dioxide emissions, because both compounds have a shorter lifespan in the atmosphere than carbon dioxide. Once released by burning wood or fossil fuels, a molecule of carbon dioxide can stay in the air for a hundred years or longer. On the other hand soot and smog cycle back out of the atmosphere much more quickly, and could buy time as longer-term solutions to eliminate carbon emissions go into effect.

The European Union already recognizes the importance of greenhouse gases like soot and smog, and plans to reduce these pollutants as part of the EU’s long-term climate strategy. Though the United States lacks an EU-style comprehensive climate plan, the US could sharply curb soot and smog by retiring old coal plants grandfathered in under the Clean Air Act during the 1970s. Such a move would also have immediate public health benefits, as these same coal plants emit toxins harmful to human health. Eliminating the nation’s worst polluters will address multiple serious problems at once, climate change caused by soot and smog pollution being only one of them.

Photo credit: Paul J. Everett