Cutting Specific Pollutants Would
Slow Sea Level Rise
4/10/2013 - National Center for Atmospheric Research (NCAR) -
BOULDER – With coastal areas bracing for rising sea
levels, new research indicates that cutting emissions of certain
pollutants can greatly slow down sea level rise this century.
The research team found that reductions in four pollutants that
cycle comparatively quickly through the atmosphere could temporarily
forestall the rate of sea level rise by roughly 25 to 50 percent.
avoid potentially dangerous sea level rise, we could cut emissions
of short-lived pollutants even if we cannot immediately cut carbon
dioxide emissions,” says Aixue Hu of the National Center for
Atmospheric Research (NCAR), the first author of the study.
new research shows that society can significantly reduce the threat
to coastal cities if it moves quickly on a handful of pollutants.”
The study, a collaboration of the Scripps Institution for
Oceanography, NCAR, and Climate Central, is being published this
week in the journal Nature Climate Change.
It was funded by the
National Science Foundation and the Department of Energy.
“It is still not too late, by stabilizing carbon dioxide
concentrations in the atmosphere and reducing emissions of
shorter-lived pollutants, to lower the rate of warming and reduce
sea level rise,” says Veerabhadran Ramanathan of Scripps, who led
“The large role of the shorter-lived pollutants is
encouraging since technologies are available to drastically cut
-----Protecting the coasts-----
The potential impact of rising oceans on populated areas is one of
the most concerning effects of climate change. Many of the world’s
major cities, such as New York, Miami, Amsterdam, Mumbai, and Tokyo,
are located in low-lying areas by the water.
As glaciers and ice sheets melt and warming oceans expand, sea
levels have been rising by an average of about 3 millimeters
annually in recent years (just more than one-tenth of an inch).
temperatures continue to warm, sea levels are projected to rise
between 18 and 59 centimeters (7 to 23 inches) this century,
according to a 2007 assessment by the Intergovernmental Panel on
Climate Change. Some scientists, however, feel those estimates are
Such an increase could submerge densely populated coastal
communities, especially when storm surges hit.
Despite the risks, policy makers have been unable to agree on
procedures for reducing emissions of carbon dioxide.
With this in
mind, the research team focused on emissions of four other
heat-trapping pollutants: methane, tropospheric ozone,
hydrofluorocarbons, and black carbon.
These gases and particles last
anywhere from a week to a decade in the atmosphere, and they can
influence climate more quickly than carbon dioxide, which persists
in the atmosphere for centuries.
Previous research by Ramanathan and Yangyang Xu of Scripps, a
co-author of the new paper, has shown that a sharp reduction in
emissions of these shorter-lived pollutants beginning in 2015 could
offset warming temperatures by up to 50 percent by 2050.
Applying those emission reductions to sea level rise, the new
research found that the cuts could dramatically slow rising sea
Their results showed that total sea level rise would be
reduced by an estimated 22 to 42 percent by 2100, depending on the
extent to which emissions were reduced.
However, the new study also found that delaying emissions cuts until
2040 would reduce the beneficial impact on year-2100 sea level rise
by about a third.
If society were able to substantially reduce both emissions of
carbon dioxide as well as the four other pollutants, total sea level
rise would be lessened by at least 30 percent by 2100, the
The researchers used mostly percentage changes for sea level rise,
rather than actual estimates in centimeters, because of
uncertainties over future temperature increases and their impacts on
rising sea levels.
“We still have some control over the amount of sea level rise that
we are facing,” Hu says.
Another co-author, Claudia Tebaldi of Climate Central, adds:
"Without diminishing the importance of reducing carbon dioxide
emissions in the long term, this study shows that more immediate
gains from shorter-lived pollutants are substantial.
emissions of those gases could give coastal communities more time to
prepare for rising sea levels.
As we have seen recently, storm
surges in very highly populated regions of the East Coast show the
importance of both making such preparations and cutting greenhouse
To conduct the study, Hu and his colleagues turned to the NCAR-based
Community Climate System Model, as well as a second computer model
that simulates climate, carbon, and geochemistry.
They also drew on
estimates of future emissions of heat-trapping gases under various
social and economic scenarios and on computer models of melting ice
and sea level rise.
The study assumes that society could reduce emissions of the four
gases and particles by 30 to 60 percent over the next several
That is the steepest reduction believed achievable by
economists who have studied the issue at Austria’s International
Institute for Applied Systems Analysis, one of the world’s leading
research centers into the impact of economic activity on climate
“It must be remembered that carbon dioxide is still the most
important factor in sea level rise over the long term,” says NCAR
scientist Warren Washington, a co-author.
“But we can make a real
difference in the next several decades by reducing other emissions.”
The University Corporation for Atmospheric Research manages the
National Center for Atmospheric Research under sponsorship by the
National Science Foundation.
Any opinions, findings and conclusions,
or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National
About the article
Title: Mitigation of short-lived climate pollutants slows sea-level
Authors: Aixue Hu, Yangyang Xu, Claudia Tebaldi, Warren M.
Washington, and Veerabhadran Ramanathan (corresponding author)
Publication: Nature Climate Change
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