• Air pollution, both outdoors and indoors, causes millions of premature deaths each year. The deaths are mainly caused by the inhalation of particulate matter.
• Black carbon, a component of particulate matter, is especially dangerous to human health because of its tiny size.
• But black carbon not only has impacts on human health, it also affects visibility, harms ecosystems, reduces agricultural productivity and exacerbates global warming.
• The breathing in of particulate matter (composed of black carbon, sulfate, nitrates, ammonia, sodium chloride, mineral dust and water) that measures 10 microns or less in diameter (PM10), poses the greatest health risks because the particles can find their way deep into lungs and the bloodstream, and cause cardiovascular and respiratory disease, and premature death.
• A major constituent of soot, black carbon is the most solar energy-absorbing component of particulate matter and can absorb one million times more energy than CO2.
• In other words, black carbon is the second largest contributor to climate change after CO2. But unlike CO2, which can stay in the atmosphere for hundreds to thousands of years, black carbon, because it is a particle, remains in the atmosphere only for days to weeks before it returns to earth with rain or snow.
• Because black carbon absorbs solar energy, it warms the atmosphere. When it falls to earth with precipitation, it darkens the surface of snow and ice, reducing their albedo (the reflecting power of a surface), warming the snow, and hastening melting.
• Black carbon, like all particles in the atmosphere, also affects the reflectivity, stability and duration of clouds and alters precipitation. Depending on how much soot is in the air and where black carbon sits in the atmosphere, it has different effects.
• If it absorbs heat at the level where clouds are forming, they will evaporate.
• When it lies above lower stratocumulus clouds that block the sun, it stabilizes them and thus has a cooling effect.
• Because black carbon interacts with other components of particulate matter, such as sulfates and nitrates that reflect sunlight and cool the atmosphere, scientists do not know exactly how much black carbon itself directly contributes to global warming.
• Developing countries in Asia, Africa and Latin America emit more than 75 percent of global black carbon emissions, mainly from cookstoves and the burning of solid fuels like coal and wood for heating, which especially affects the health of women and girls.
• Diesel vehicles and open biomass burning, the largest global source of black carbon, also contribute significant emissions.
• Snow covered regions are the most vulnerable to the warming effects of black carbon, and any particles reaching them are of concern if they are darker than snow, because they can reduce reflectivity and speed melting.
• Other efforts are being made to curb black carbon emissions as well. At the Paris climate talks in December, the Climate and Clean Air Coalition comprised of government and industry groups, agreed on plans to tackle the emissions of “short-lived climate pollutants” which include black carbon, HFCs, methane and ground-level ozone.
• To reduce black carbon emissions, it is working to increase the number of countries to 40 involved in Green Freight Action Plans by 2018.

Green Freight Action Plan:

• The Green Freight Action Plan aims to increase awareness about black carbon emissions, develop methods to track and report black carbon emissions and spur the adoption of technologies and best practices to reduce them.
• A side event at the climate conference focused on the Arctic Council’s initiatives to curb black carbon and methane emissions, mainly arising from cooking, heating, transportation including shipping, and the flaring of methane that leaks from oil and gas wells in the region.
• It highlighted efforts to deal with sources of black carbon, reduce emissions from wood burning for heating and convert diesel transport.
• The Arctic Council’s states (countries with territory in the arctic—Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden and the United States) and Arctic Council Observers are estimated to be responsible for around 50 percent of manmade global emissions of black carbon and methane.

Source: Columbia.edu