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Reducing Black Carbon and Other Short-Lived Climate Pollutants Could Reduce Sea Level Rise by a Third

But that's bad news for the world's air conditioning addiction.
Image: NOAA

Recently we learned that nearly 3.5 million people are killed each year by indoor air pollution, much of it caused by black carbon soot. It's a health problem for sure, and it's a climate change problem, both of significant size—despite the general lack of media attention focused on either aspect.

Now, a well-timed report coming out of the National Center for Atmospheric Research really shows the very powerful effect that reducing black carbon (that purple haze in the image above), as well as other short-lived air pollutants, can significantly slow sea level rise. The pollutants: methane, tropospheric ozone, hydrofluorocarbons, and black carbon.

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Compared to carbon dioxide all of these pollutants come out of the air quickly—particularly black carbon—lasting anywhere from a few weeks in the atmosphere to a couple decades, versus the centuries CO2 can last. So reducing the emissions of all these can have a much more rapid effect than can cutting CO2—though reducing that is still critical as it's the dominant greenhouse gas which humans have any control over.

How much can cutting these pollutants reduce warming and slow our rising seas? The scientists found that by cutting back on all these pollutants can temporarily slow sea level rise by about 25 to 50 percent, due to slowing temperature rise. By 2100, if we cut back on these pollutants, as well as reduce carbon dioxide emissions, sea level rise over the coming century can be reduced by at least 30 percent.

Previous research looking just at the effect that reducing black carbon pollution found that Arctic warming could be cut two-thirds by 2030 by doing so, with a decrease in warming of 0.5C.

But we have to act quickly: To slow sea level rise that much, we have to essentially start cutting down on these pollutants right now. Delaying action until 2040 reduces the potential for reducing sea level rise by one-third.

What does that mean for coastal cities? We're not talking about sea levels being three feet higher than today—to use a pretty middle-of-the-road estimate—rather just about two feet, or potentially less. Something some of the world's most populous cities would still have to take very seriously, but it would give them more time to prepare.

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Where's this pollution coming from?

Black carbon pollution comes from a couple of main sources: Older cooking stoves burning wood, dried dung, some other form of biomass; older diesel engines. There have been ongoing efforts to replace these older cookstoves with similar newer models that both use less fuel and reduce emissions, but they have yet to show clear results—old habits and preferences are hard to break.

Methane, again, comes from a variety of sources: leaks in natural gas production are an easily remedied source; as is capturing it from landfills. Less easy, at least technologically, is reducing methane associated with livestock agriculture—though reducing the amount of meat and dairy we eat is a good start. Stopping methane from permafrost melting and seeping up from the ocean floor, both caused by global warming, is much more problematic to stop.

Tropospheric ozone--which is different in location that the ozone that's responsible for all sorts of health problems, as well the ozone layer higher up in the atmosphere that we want to keep intact--comes the reaction of nitrogen oxides, carbon monoxide, and volatile organic compounds in the presence of sunlight. Reducing tailpipe emissions from motor vehicles, reducing industrial emissions, as well as chemical solvents can help here.

Hydrofluorocarbons, used to replace the ozone layer-depleting CFCs, have a seriously high warming potential, even compared to methane. Unfortunately demand for them is expected to increase in the coming decades as more of the world decides, like the United States has, that using air conditioning is the best thing since indoor plumbing. HFCs also come from a variety of industrial processes. It's worth noting that previous research by the EPA has shown that phasing out HFCs altogether could slow global warming by a decade.