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Cutting Short-lived Pollutants Can Slow Sea Level Rise

A new study finds that it is possible to greatly slow the rate of sea level rise, which is one of the biggest threats global warming poses, by cutting so-called “short-lived climate pollutants,” which warm the climate on timescales of a few weeks to a decade, in combination with reductions in long-lived greenhouse gases such as carbon dioxide (CO2). 

The study, published in the journal Nature Climate Change, found that reducing emissions of these short-lived climate pollutants, including soot and methane, by 30 to 60 percent by 2050 would slow the annual rate of sea level rise by about 18 percent by 2050. Combining reductions in short-lived pollutants with decreasing CO2 emissions could cut the rate of sea level rise in half by 2100, from 0.82 inches to 0.43 inches per year, while reducing the total sea level rise by 31 percent during the same period. 

Related research by Climate Central scientists shows that the emissions reductions would potentially benefit more than 2 million Americans by 2100, who might otherwise be living below sea level at that point. 

For more information on the methods behind this interactive, click here.

In addition, the study found that, compared to just cutting CO2 emissions, reducing the release of short-lived climate pollutants would do more to slow sea level rise before 2050, but that lowering CO2 emissions would be required to limit warming and warming-related impacts beyond that point. 

“We need an all-of-the-above approach to controlling greenhouse gases. Clearly we need to cut CO2 emissions, but we also need to take advantage of the very substantial short term gains that can be achieved by cutting emissions of non-CO2 climate pollutants,” said Claudia Tebaldi, a research scientist at Climate Central and a co-author of the study.

As ocean waters warm and land-based ice sheets melt in response to manmade global warming, global sea levels have been rising by about 1.2 inches per decade, and recent studies project up to 1 meter, or about 3.3 feet, of global sea level rise by the end of this century. This would imperil some of the world’s largest coastal population centers, including New York, Miami, and Mumbai. In the U.S., Florida has the greatest population at risk from sea level rise, with 2.1 million people projected to live below sea level in that state by 2100 if greenhouse gas emissions are not reduced. 

Sea level rise will vary in different regions of the world due to ocean currents and movement of land masses, but this study examined global average sea level rise.

Already, sea level rise has made storm surge events more damaging than they otherwise would have been. In New York, for example, seas have risen by about one foot during the past century, which helped heighten the storm surge from Hurricane Sandy when the storm struck in October 2012. That storm killed more than 40 people in New York City itself, flooded all of the subway tunnels that connect Manhattan to Brooklyn and Queens, and cut power to lower Manhattan for days.

Carbon Dioxide Reductions Crucial For Addressing Long-Term Climate Change

Carbon dioxide emissions remain in the atmosphere for centuries, which makes it the most important greenhouse gas to reduce in order to limit long term climate change, but for the first time, this new study showed that cutting short-lived pollutants can also ease some impacts during the next few decades. 

A wildfire at the Yugansky Nature Reserve in northern Russia in 2012. Wildfires in northern Russia are a significant source of black carbon, or soot, pollution.
Credit: ressaure/Flickr.

Previous work has examined the overall warming influence of short-lived pollutants and found that cutting the four key pollutants - black carbon (soot), methane, tropospheric ozone, and hydrofluorocarbons, also known as HFCs — can offset warming temperatures by up to 50 percent by 2050. These pollutants are emitted from a variety of sources, from biomass-burning cookstoves and forest fires to natural gas pipeline leaks.

This new study used computer models to estimate how the oceans would respond to global warming, and also used estimates of future emissions of heat-trapping gases. The study acknowledges the wide range of projections of future sea-level rise, owing in part to a lack of understanding of how the massive land-based ice sheets such as Greenland and Antarctica will respond to global warming. 

Instead of trying to arrive at a particular projection of sea level rise, as other researchers have done, the study focused on how pollution reductions would change the course of sea level rise. 

Benjamin Horton, a professor at the University of Pennsylvania who studies sea level rise and was not involved in the study, said this approach was “simple,” and yet provides for a convincing case that tackling short-lived pollutants is important for slowing climate change in the next few decades. “They tackled the problem of sea level [rise] very simply and I think appropriately for this question,” he said in an interview.

Veerabhadran Ramanathan, the lead author of the study and a scientist at the Scripps Institution of Oceanography, told Climate Central that there is a need to address both short-lived pollutants and CO2 in order to avoid the worst near and long-term impacts from global warming. 

“We cannot do it with CO2 alone,” he said. “By not taking actions about two decades ago, we have lost the luxury of doing one thing at a time. We have to reduce both CO2 and short-lived climate pollutants.”

In addition to slowing sea level rise, research has shown that reducing short-lived climate pollutants such as black carbon (which is largely generated from wood and dung-burning cook stoves in developing countries) would also have major public health benefits, saving up to 4.7 million lives worldwide per year. 

Soot emissions can be reduced through the use of cleaner-burning cookstoves that don’t rely on burning biomass for fuel, as well as cutting the use of dirty forms of diesel fuel. Methane emissions can be reduced by controlling leaks from natural gas pipelines, and using different agricultural practices.

Editor's Note: Climate Central's editorial staff operates a news service that is journalistically independent of the organization's research and communications programs. For more information see our "what we do" section.

Related Content:
Short-Lived Pollutants Are Key to Slowing Sea Level Rise
Surging Seas: Sea Level Rise Analysis by Climate Central
Black Carbon Second Only to CO2 in Warming the Planet
Groundbreaking New Study Shows How to Reduce Near-Term Global Warming
The Story Behind Recent Ice Loss in Greenland

Comments

By dan_in_illinois
on April 14th, 2013

I must have misread the article.  I could have sworn they said that if we do absolutely nothing, the sea level will rise by 0.82 inches by the year 2100.  If I did read this correctly, that means the “experts” are getting themselves worked into a lather over the rise of the oceans of a fraction of an inch over 8 decades.  Perhaps one of the true believers can help explain things to me.

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By catman306 (NE Georgia, USA)
on April 15th, 2013

You missed the part that said 0.82 inches PER YEAR.

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By dan_in_illinois
on April 15th, 2013

My mistake.

But that creates a new question.  If the sea level is rising 0.82 inches per year, it would seem that this is easily observable.  Did the “experts” measure an almost 1 inch rise in sea level last year?  How about the year before?  We’ve been releasing all of these gases into the atmosphere for decades.  By now the Atlantic Ocean should have engulfed most of Florida.

Reply to this comment

By climatelurker
on April 15th, 2013

dan_in_illinois:

You did read it incorrectly.  What the article said was, “...could cut the rate of sea level rise in half by 2100, from 0.82 inches to 0.43 inches per year.”

I’ll translate that for you.  By 2100, without decreasing short term pollutants, sea levels may rise by 63 inches (that’s more than 5 feet).  If pollution is reduced, that could be cut in half, so it would be 33 inches instead (less than 3 feet).

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By dan_in_illinois
on April 15th, 2013

climatelurker:

Thanks for the translation.  My question remains - if the sea is actually supposed to be rising at a little less than 1 inch a year for several decades now, where is the evidence?  As I said, at that rate, the waters should be engulfing the state of Florida by now.

Reply to this comment

By Dave (Basking Ridge, NJ 07920)
on April 15th, 2013

The current rate of global GHG emissions is accelerating. My own question for anyone with access to the full paper, or maybe Andrew, is what defines BAU in these particular analyses? Did the BAU emissions scenario used here assume a flat continuation of today’s global emission rates or did it instead assume a continuation of the current rate of increase in the rate of emissions and so on? What was the assumed shape of the BAU curve? There is a lot of serious discussion going on about exactly what are realistic projections of global GHG emissions, particularly when it comes to when peak emissions will be reached. Conservative versus less conservative assumptions for BAU make a really significant difference.

Regarding prior comments on the rates of SLR:

The rate of SLR is currently measured to be about 0.12 inches per year. That’s almost twice the 20th century average rate. The RATE that the mean global sea level is rising is therefore known to be increasing.  In other words, sea level is accelerating.

Compared with that, the models discussed here project that the rate of SLR will continue to increase from what it is today throughout the 21st century under a business as usual scenario – whatever that was assumed to be - to a value of 0.82 inches per year by 2100. That would then be almost 7 times faster than it is today.

See for instance figure 2 in the abstract for the article discussed here, where you can see that the slope of the curve increases with time:
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1869.html
As far as I can tell, that figure indicates a BAU projected SLR of about 1.3 m by 2100.

One thing that seems not to get publicly discussed too much about sea level rise is that, in all the model results I have seen, whatever the precise projected rates and levels are in 2100, the mean sea level does not suddenly stop rising in 2100. For instance, another page at the nature.com site provides a bit more background on the general subject of SLR and the figure 3 there shows some estimates of possible SLR for the next 300 years.
http://www.nature.com/scitable/knowledge/library/modeling-sea-level-rise-25857988
Notice that none of the projections shown there indicate any leveling off of the rate of sea level rise out to 2300.

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By dan_in_illinois
on April 16th, 2013

I’m still looking for an answer here.  If the seas will rise in the future at a rate of 0.82 inches per year due to pollutants, and if those pollutants have been released at approximately the same rate during these last several decades, then why aren’t the coastal cities of Florida underwater by now?

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By Dave (Basking Ridge, NJ 07920)
on April 16th, 2013

Sure Dan, much of Florida is close to sea level and therefore at greater risk from SLR. So are parts of New York and other large swaths of heavily populated sections of the eastern seaboard, most of London, Shanghai, many other coastal cities and regions, pretty much all of the Federated States of Micronesia which are islands out there in the Pacific, PNG and so on and so on.

The short answer to your question is that these pollutants, CO2 in particular, accumulate over time. The rate of global warming therefore increases over time adding heat to our planet at a greater and greater rate. It takes time to warm up a planet so there is a time lag, like waiting for the kettle to boil, only in this case the ‘kettle’ is planet sized. You are apparently wondering why it didn’t happen a lot faster. Most other people are instead surprised and concerned that it is happening as fast as it is.

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