Thawing permafrost soils in the rapidly warming Arctic will emit as much greenhouse gas as large industrial nations by the end of this century, according to a University of Alberta researcher involved in an international study that stresses to policy makers that it’s not too late to act to stabilize the climate and avoid exceeding temperature targets.
“If we avoid the worst-case scenarios of warming, our assessment shows that emissions from thawing permafrost are still going to be equivalent to somewhere between 60 and 80 billion tonnes of carbon over the next 80 years, which is a rate similar to current-day carbon dioxide emissions from Western Europe,” says scientist David Olefeldt of the Faculty of Agricultural, Life & Environmental Sciences, the lone Canadian co-author on the research.
Olefeldt explains that carbon storage in permafrost is simply a function of thousands of years of plant material that has become a frozen part of the soil and doesn’t decompose if left alone. “It's basically like putting things in a freezer — it'll stay there for a long time until you start thawing it out and exposing it to microbial degradation.”
As carbon storage goes, permafrost is a major player, storing more than twice as much carbon as is currently found in the atmosphere.
Led by Northern Arizona University and the international Permafrost Carbon Network, the study draws on more than a decade’s worth of data from permafrost field work from around the globe to forecast cumulative emissions from this “country of permafrost” through 2100 under low, medium and high warming scenarios.
The team estimates that under a low warming scenario — one that could be achieved if the global community limited warming to 2 C — permafrost would release 55 billion tonnes of carbon by the end of the century in the form of carbon dioxide and methane. If nothing is done to mitigate climate warming, the study estimates the Arctic could release nearly five times that amount, which is twice the amount of carbon-dioxide equivalent emissions the United States has released since its industrial rise to power began 150 years ago.
All told, the study describes nine future scenarios based on how climate warming progresses and what actions global leaders take to reduce fossil fuel emissions.
Olefeldt, whose research teams have been responsible for many permafrost field studies coming out of Canada’s North that were used in the study, adds while it is important to emphasize how large the emissions could be under the warmest conditions, there is no scenario where carbon emissions from continued permafrost thaw will surpass the human-made problem.
“It's not something that's going to cause runaway climate change, but it definitely adds an accelerant to climate change and is an important component of the future greenhouse gas budget for the world,” he explains.
“The more we are able to restrain human emissions and thereby avoid the worst-case scenarios of warming, the more carbon is going to stay in the ground in the Arctic.”
The authors emphasize that ongoing international efforts to reduce emissions must account for this “country of permafrost” in climate targets and actions.
The study also outlines uncertainties in estimating future greenhouse gas emissions from thawing permafrost. Abrupt thaw, when permafrost thaw causes land surface collapse, can lead to large greenhouse gas emissions, but only one-fifth of current permafrost terrain is believed to be vulnerable to abrupt thaw. It’s also uncertain whether thaw will lead to wetter or drier soils, which matters because wetter soils promote emissions of methane, a more potent greenhouse gas.
And as the second largest Arctic country, Canada will be home to much of this coming emissions surge, which is expected to last many centuries, Olefeldt says.
“Even if we stopped fossil fuel emissions halfway through this century, the Arctic is going to keep responding for hundreds of years after that.”
The study was published in the Annual Review of Environment and Resources.