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NOAA-led study find ship air pollution plummets when vessels shift to low-sulfur fuels and slow down; net warming impact

Emissions reductions (per km of travel) from the Margrethe Maersk as a result of the State of California fuel sulfur regulation (gray), vessel speed reduction program (white) and combined (black). Credit: ACS, Lack et al. Click to enlarge.

New clean fuel regulations in California and voluntary slowdowns by shipping companies substantially reduce air pollution caused by near-shore ships, according to a new NOAA-led study published online in the ACS journal Environmental Science & Technology.

The study also discusses the net radiative (warming vs. cooling) effect of the fuel switch. Changes in the emissions of various air pollutants—some which have a warming effect, others which have cooling effects—likely mean net warming, the team concluded.

The study examined a container ship operating under a 2009 California regulation requiring that ships switch to low-sulfur fuels as they approach the California coast, and also adhering to a voluntary state slowdown policy, intended to reduce pollution. The research team found that emissions of several health-damaging pollutants, including sulfur dioxide and particulate matter, dropped by as much as 90%.

Reduction in emission factors (EFs) of sulfur dioxide (SO2), particulate matter, particulate sulfate and cloud condensation nuclei were substantial (≥90%). EFs for particulate organic matter decreased by 70%. Black carbon (BC) EFs were reduced by 41%. When the measured emission reductions, brought about by compliance with the California fuel quality regulation and participation in the vessel speed reduction (VSR) program, are placed in a broader context, warming from reductions in the indirect effect of SO4 would dominate any radiative changes due to the emissions changes. Within regulated waters absolute emission reductions exceed 88% for almost all measured gas and particle phase species.

—Lack et al.

Findings of this study could have national and global significance, as new international regulations by the International Maritime Organization require vessels to switch to lower-sulfur fuel near US and international coasts beginning in 2012. The research team found reductions in emissions even where none were expected, meaning even greater reductions in air pollution, and associated respiratory health effects in humans, than regulators originally estimated.

In May 2010, a NOAA research aircraft flew over a commercial container ship, Maersk Line’s Margrethe Maersk, about 40 miles off the coast of California. Researchers on the aircraft used sophisticated custom instruments to ‘sniff’ the ship’s emissions before the ship switched to lower-sulfur fuels (by law, within 24 miles of the California coast) and slowed down voluntarily.

A few days later, scientists aboard the NOAA-sponsored Woods Hole Oceanographic Institute’s research vessel Atlantis sampled emissions of the same ship as it cruised slowly within the low-sulfur regulated zone.

Sulfur dioxide levels, which were expected to drop, did do so, plummeting 91% from 49 grams of emissions per kilogram of fuel to 4.3 grams. Sulfur dioxide is best known as a precursor to acid rain, but can degrade air quality in other ways, directly and indirectly through chemical reactions in the atmosphere. In particular, emissions of sulfur dioxide lead to formation of particulate matter in the atmosphere which poses serious public health concerns.

Particulate matter pollution, regulated because it can damage people’s lungs and hearts, dropped 90% from 3.77 grams of emissions per kg of fuel to 0.39 grams.

Unexpectedly, black carbon levels also dropped, cut by 41%, the team reported. Black carbon comprises dark-colored particles that can warm the atmosphere and also degrade air quality.

In 2009, the US Environmental Protection Agency and its Canadian equivalent, Environment Canada, estimated that shifting to low-sulfur fuels near coasts could save as many as 8,300 lives per year in those two countries, and ease the acute respiratory symptoms faced by another 3 million. But that 2009 assessment did not include the observed drops in several pollutant categories that Lack and his colleagues found, so the authors suggest the impacts could be greater.

The project was funded by NOAA and the California Air Resources Board and conducted in close collaboration with the Maersk Line.


  • Daniel A. Lack, Christopher D. Cappa, Justin Langridge, Roya Bahreini, Gina Buffaloe, Charles Brock, Kate Cerully, Derek Coffman, Katherine Hayden, John Holloway, Brian Lerner, Paola Massoli, Shao-Meng Li, Robert McLaren, Ann M. Middlebrook, Richard Moore, Athanasios Nenes, Ibraheem Nuaanan, Timothy B. Onasch, Jeff Peischl, Anne Perring, Patricia K. Quinn, Tom Ryerson, Joshua P. Schwartz, Ryan Spackman, Steven C. Wofsy, Doug Worsnop, Bin Xiang, Eric Williams (2011) Impact of Fuel Quality Regulation and Speed Reductions on Shipping Emissions: Implications for Climate and Air Quality. Environmental Science & Technology doi: 10.1021/es2013424



Be careful what you wish for.


If we want cooling, we can build oxygen-blown IGCC plants, capture the H2S, put it in huge artillery shells mixed with a bit of propane, launch them into the stratosphere with syngas-burning gas guns, and burn it to SO2 on the spot. Recovery of the shells by flyback parasails would complete the cycle.

Only small amounts of sulfur would be required for this (the lifespan in the stratosphere is several years), so the ground-level pollution impact would be negligible.

Nick Lyons

@Engineer-Poet: I believe you really are an engineer.


Yup, guilty as charged. I'm willing to engineer the climate too, if that's what it takes.

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