Unless humans reduce fossil fuel emission drastically, warming temperatures will cause up to two-thirds of the earth's permafrost to disappear by 2200, unleashing large amounts of carbon into the atmosphere, says a new study by the University of Colorado Boulder's Cooperative Institute for Research in Environmental Sciences, published this week in the scientific journal Tellus.
Warming temperatures are causing permanently frozen ground to thaw in high latitudes, says 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 says. "Otherwise we will end up with a warmer earth than we want."
The escaping carbon comes from plant material, primarily roots frozen in soil during the last glacial period that ended roughly 12,000 years ago, Schaefer says. He 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."
The study 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."
Schaefer and his team estimate roughly 190 billion tons of carbon will be released from the permafrost, most of it in the next 100 years. "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," says 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.
There were about 280 parts per million of CO2 in the earth's atmosphere before the Industrial Age began around 1820. There are more than 380 parts per million of
carbon in the atmosphere now, and the figure is rising. The increase, equivalent to about 435 billion tons of carbon, resulted primarily from human activities such as burning fossil fuels and deforestation. Most climate scientists believe that buildup of CO2 and other greenhouse gases is the primary reason for increasingly warm temperatures. Last year tied for the hottest year on record. The hottest decade on record occurred from 2000 to 2010.