Up to two-thirds of Earth's permafrost likely will disappear by
2200 as a result of warming temperatures, unleashing vast
quantities of carbon into the atmosphere, says a new study by the
University of Colorado Boulder's Cooperative Institute for Research
in Environmental Sciences.
The carbon resides in permanently frozen ground that is
beginning to thaw in high latitudes from warming temperatures,
which will impact not only the climate but also international
strategies to reduce fossil fuel emissions, said CU-Boulder's Kevin
Schaefer, lead study author. "If we want to hit a target carbon
dioxide concentration, then we have to reduce fossil fuel emissions
that much lower than previously thought to account for this
additional carbon from the permafrost," he said. "Otherwise we will
end up with a warmer Earth than we want."
The escaping carbon comes from plant material, primarily roots
trapped and frozen in soil during the last glacial period that
ended roughly 12,000 years ago, he said. Schaefer, a research
associate at CU-Boulder's National Snow and Ice Data Center, an arm
of CIRES, likened the mechanism to storing broccoli in a home
freezer. "As long as it stays frozen, it stays stable for many
years," he said. "But if you take it out of the freezer it will
thaw out and decay."
While other studies have shown carbon has begun to leak out of
permafrost in Alaska and Siberia, the study by Schaefer and his
colleagues is the first to make actual estimates of future carbon
release from permafrost. "This gives us a starting point, and
something more solid to work from in future studies," he said. "We
now have some estimated numbers and dates to work with."
The new study was published online Feb. 14 in the scientific
journal Tellus. Co-authors include CIRES Fellow and Senior
Research Scientist Tingjun Zhang from NSIDC, Lori Bruhwiler of the
National Oceanic and Atmospheric Administration and Andrew Barrett
from NSIDC. Funding for the project came from NASA, NOAA and the
National Science Foundation.
Schaefer and his team ran multiple Arctic simulations assuming
different rates of temperature increases to forecast how much
carbon may be released globally from permafrost in the next two
centuries. They estimate a release of roughly 190 billion tons of
carbon, most of it in the next 100 years. The team used
Intergovernmental Panel on Climate Change scenarios and
land-surface models for the study.
"The amount we expect to be released by permafrost is equivalent
to half of the amount of carbon released since the dawn of the
Industrial Age," said Schaefer. The amount of carbon predicted for
release between now and 2200 is about one-fifth of the total amount
of carbon in the atmosphere today, according to the study.
While there were about 280 parts per million of CO2 in Earth's
atmosphere prior to the Industrial Age beginning about 1820, there
are more than 380 parts per million of carbon now in the atmosphere
and the figure is rising. The increase, equivalent to about 435
billion tons of carbon, resulted primarily from human activities
like the burning of fossil fuels and deforestation.
Using data from all climate simulations, the team estimated that
about 30 to 60 percent of Earth's permafrost will disappear by
2200. The study took into account all of the permanently frozen
ground at high latitudes around the globe.
The consensus of the vast majority of climate scientists is that
the buildup of CO2 and other greenhouse gases in Earth's atmosphere
is the primary reason for increasingly warm temperatures on Earth.
According to NOAA, 2010 was tied for the hottest year on record.
The hottest decade on record occurred from 2000 to 2010.
Greater reductions in fossil fuel emissions to account for
carbon released by the permafrost will be a daunting global
challenge, Schaefer said. "The problem is getting more and more
difficult all the time," he said. "It is hard enough to reduce the
emissions in any case, but now we have to reduce emissions even
more. We think it is important to get that message out now."
SOURCE
