But current technology can reduce ship pollution 90%, and a House committee is weighing law to reduce black carbon emissions.

In the next few decades, a warming Arctic will open up shorter shipping routes, potentially reducing the amount of fuel needed to travel between ports. But the increased amount of soot in the atmosphere could further accelerate the region's climate change, and the shorter distances won't generate enough fuel savings to offset the impact.

Those are the key findings of a recent study published in the journal Atmospheric Chemistry and Physics. This new study is the first systematic analysis of how Arctic shipping could affect local climate.

About 15,000 ship trips occur in the Arctic region (north of 60° latitude) each year, but they comprise a small fraction of global shipping. Melting sea ice could create ice-free passages by 2030 and create shortcuts for global trade. Two of the most anticipated routes are the Northwest Passage linking Japan to eastern Canada, and the Northeast Passage along Russia's northern coast, which would connect China with Europe.

Increased ship traffic will bring additional air pollution to the Arctic. Of particular concern is black carbon, a form of particulate matter emitted through the burning of fossil fuels.

"Black carbon is—in my opinion—the second leading cause of global warming after carbon dioxide," said Mark Jacobson, a professor of civil and environmental engineering at Stanford University, who was not involved in the study.

Today's shipping industry produces 42 million tons of carbon dioxide annually, versus only 4 million tons of black carbon. But the cumulative effects of black carbon can add substantially to those of carbon dioxide from Arctic ships: over a short-term period such as 20 years, one ton of black carbon emitted in the Arctic can produce a similar warming effect as 4,000–7,000 tons of carbon dioxide, James Corbett, the study's lead author, told SolveClimate News. Corbett is a professor of marine policy in the College of Earth, Ocean and Environment at the University of Delaware.

Short-Lived But Potent Pollutant

Black carbon warms the earth in two ways. First, atmospheric black carbon absorbs sunlight and heats up the air around it. Particles of black carbon can also fall to the ground and accelerate melting by decreasing albedo, or surface reflectivity. Ice and snow reflect much more sunlight than the ocean, so the more ice that melts, the more water there is to absorb heat. The result, said Jacobson, is a positive feedback loop that will speed up Arctic warming.

Unlike carbon dioxide, which can remain in the atmosphere for 100 years, a single particle of black carbon rarely lasts more than three weeks before it's rained out of the atmosphere and deposited on the ground. (The one exception is black carbon emitted by planes that fly over the Arctic; the planes fly in a higher level of the atmosphere called the stratosphere, where the air is more stable. As a result, stratospheric black carbon can last for months or even years.)

However, Corbett said, the cumulative effect of ground emissions provides a continuous source of black carbon that's transported from populated places like Europe to the Arctic, and the emissions will only increase as sea lanes open up.

Although the new routes would cut down on ships' CO2 emissions, those reductions would be offset by the effects of black carbon, said Corbett. "It won't benefit the Arctic…[because the black carbon emissions] would be in a place where you would least want them."

The Arctic is particularly sensitive to climate change. While global temperatures have risen by an average of 0.7° C due to anthropogenic warming, the Arctic has warmed 2.0-2.5° C.

"Those ships will be emitting black carbon pollution right near the glaciers and the sea ice where they can do the most damage," said David Marshall, senior council for the Clean Air Task Force, a nonprofit committed to air quality and climate issues. The Task Force helped support Corbett's work but Marshall did not work directly with the study's authors.

Marshall called the study "the most up-to-date survey of shipping emissions in the Arctic." He believes the research "can provide a firm foundation for policy makers trying to assess the impact of those emissions."

Growth Rate Influences Emissions Scenarios

Corbett and his colleagues began by producing an inventory of emissions from the 15,000 ship trips that occur annually in the Arctic. They used data from the year 2004, which came out of the Arctic Marine Shipping Assessment, an international study that catalogued the vessels based on type, fuel source and estimated emissions.

The next step was to model future scenarios for Arctic shipping: one involved a "business as usual" growth, and a second envisioned a fast expansion in the shipping industry.

Under the fast-growth scenario, by 2030 the addition of black carbon emissions
could increase the warming potential of the Arctic ships' CO2 by 17 percent to 78 percent.

Corbett cautioned that more research is needed to refine these numbers. What's more important is the potential for mitigation: in both scenarios, the researchers projected that control measures based on current technology could reduce black carbon-caused warming by 90 percent.

Similar reductions are being seen with technologies already being used in passenger vehicles, said Jacobson. New cars and buses often come equipped with traps that cut down on black carbon emissions by over 90 percent.

Still, Jacobson said, "it's probably not a technological issue." The real key lies in policy.

Over the past 3 years, Congress has seen four proposed laws on reducing black carbon. Two of the bills (The Arctic Climate Preservation Act and the Black Carbon Research Bill) never became law. Another bill (HR1760)—the Black Carbon Emissions Reduction Act of 2009—is being reviewed by the Subcommittee on Energy and Environment. The only successful bill was passed in 2009; it requires the EPA to research methods of reducing black carbon emissions.

Corbett hopes that his research will demonstrate the potential of mitigation. "[By adding] a controlled emission pathway like we have—it also adds to the value of future analysis," said Corbett. "Policy makers can immediately ask the question 'Would policy and intervention help?'" 

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