On the margins of the Paris climate conference, where governments made plans to keep global average temperatures below 2C (3.6F) by 2100, scientists and policymakers discussed other air pollutants that also contribute to global warming.
Emissions of carbon dioxide have a far greater role in climate change, but short-lived climate pollutants such as black carbon – soot – also speed up warming, especially in the Arctic. Black carbon is not a gas, but an aerosol, tiny particles produced from diesel trucks and cars, wildfires, agricultural burning, oil and gas production and shipping that are released into the atmosphere.
Black carbon is also causing the Earth’s climate to warm. A recent study found that black carbon is far more harmful to the climate than scientists once thought – its heat-trapping power is second only to carbon dioxide and it holds twice as much heat in the atmosphere than estimates made by the Intergovernmental Panel on Climate Change in 2007.
But as its name implies, short-lived climate pollutants such as black carbon don’t stay in the atmosphere for very long. Black carbon usually falls out of the air after about a week. If it lands on snow or ice, it darkens the surface and causes warming and melting by absorbing solar radiation instead of reflecting it. Consequently, the Arctic is very susceptible to warming that results from black carbon.
Because black carbon has a short lifetime, atmospheric concentrations can be quickly decreased by reducing emissions. Actions taken to reduce emissions could slow the rate of climate change in a short period of time.
Annual black carbon emissions have been climbing steadily since the mid-1800s. Human activities generated about 1 million tons of black carbon emissions annually in 1850. But by 2000, we were discharging 5 million tons into the atmosphere each year.
Arctic states are the source of about 30 percent of Arctic warming attributed to black carbon and the rest originates outside of the Arctic. Household heating and cooking, transport and flaring from oil and gas activities account for most anthropogenic sources of black carbon in the Arctic.
Oil companies often burn, or flare, the methane that leaks from a well during drilling. This reduces the emissions of the greenhouse gas, but it increases emissions of black carbon. In the Arctic, about 75 percent of energy-sector emissions come from flaring. Flaring emissions from Russia are the largest contributor of black carbon, followed by those in Nordic countries.
Shipping currently accounts for about 5 percent of black carbon emissions in the Arctic. Cargo ships traveling through the Arctic tend to burn heavy fuel oil. It’s a cheap, but inefficient fuel that releases soot into the air and onto the nearby snow and ice.
As Arctic sea ice retreats, shipping and oil and gas activities are expected to grow and produce more black carbon. The number of vessels in U.S. Arctic waters is projected to more than double – possibly quintuple – between 2013 and 2025, according to a study by the Committee on the Marine Transportation System. Arctic shipping emissions of black carbon could more than double by 2050 if no controls are put in place, according to the Arctic Monitoring and Assessment Programme (AMAP).
“Collectively, Arctic Council members and observer states contribute more than 60 percent of black carbon pollution. So if we want to know where the problem begins, all we have to do is look in the mirror,” U.S. secretary of state John Kerry said at the Arctic Council Ministerial Meeting in Iqaluit in April 2015.
David Balton, the chair of the Arctic Council’s senior Arctic officials, has called the need to reduce black carbon emissions “urgent.” “If we’re going to be successful in reducing these short-lived climate pollutants, we will need the cooperation of the non-Arctic states, particularly the near-Arctic states,” said Balton.
Arctic states have already committed to reducing their black carbon emissions. The Arctic Council created a non-binding scheme to inventory black carbon emissions from member states as of 2015 and adopt an ambitious goal by 2017. The observer states were also invited to do the same.
Cutting black carbon emissions could have important effects on Arctic warming. Global reductions in black carbon (and co-emitted air pollutants) could reduce Arctic warming by 0.25C (0.5F) by 2025, mostly by slowing the rate of snow and ice melt, according to a new scientific assessment by AMAP, a working group of the Arctic Council. Aggressive cuts to carbon dioxide combined with decreased black carbon emissions could reduce Arctic warming by 0.7C (1.3F) in 2050, Julia Schmale, from the Laboratory of Atmospheric Chemistry at the Paul Scherrer Institute in Switzerland, wrote recently in Nature Climate Change.
The technology to reduce emissions already exists in many cases. By switching fuels and installing scrubbers that capture the tiny particles, the shipping industry could reduce black carbon emissions by up to 70 percent.
One of the priorities during the U.S. chairmanship of the Arctic Council will be to provide small communities with access to renewable energy so that they use less diesel fuel. The oil and gas, and mining industries, especially in Russia, are additional targets.
Of course, the Arctic wouldn’t be the only beneficiary from reduced black carbon emissions. The pollutant also has a negative effect on air quality. Fewer emissions would mean cleaner air globally, and could save millions of lives.
Top image: Black carbon emissions from shipping could more than double by 2050. (Pixabay)