An enormous stockpile of carbon, locked in permafrost beneath the land and waters of Alaska, could be unleashed by rising temperatures, complicating international efforts to curb greenhouse gas emissions.
One of the mysteries of the coming decades for Alaska and other northern regions is at what pace permafrost will thaw as temperatures climb and how the release of carbon will change the climate.
A new U.S. Geological Survey study presents what many will see as a hopeful forecast, concluding the release of carbon by growing wildfires and thawing soil could be more than offset by trees and other plants taking in more carbon as they grow, particularly in Southeast Alaska. As plants grow, they remove carbon dioxide from the air.
"This increased ability to sequester carbon is expected to occur due to increased vegetation growth prompted by longer growing seasons and other more favorable conditions," the USGS said.
This is an intriguing prospect, but by no means a certainty. Even climate scientists who are experts on permafrost regions have their doubts it will play out this way for the rest of the century.
Another recent study, based on the opinions of 98 experts, concluded total plant growth will decrease and not lead to the removal of more carbon from the atmosphere.
A complex set of related factors — none of which are subject to precise calculations before they happen — are complicating efforts to tell the future.
The authors of the USGS study that says longer growing seasons and additional plant growth will absorb a large amount of carbon acknowledge this: "Similar to weather forecasting, projecting a set of biological conditions (such as carbon balance) into the future is based on hypothetical scenarios that are necessarily uncertain."
According to some estimates, the carbon stored in frozen soils in the far north is more than double the amount in the atmosphere today. As much as one-quarter of Alaska's permafrost could melt by 2100, a USGS study from late last year predicted.
David McGuire, a University of Alaska Fairbanks biologist who is one of the co-authors of the USGS report, also was one of the 98 experts consulted on the other study.
I asked him about the contradiction between the USGS report and the "expert elicitation." He said it is not so much a contradiction, but a reflection of the underlying complexity.
"The best way to characterize the results of such an elicitation is that it represents a 'prevailing scientific hypothesis' if it goes one way or another, but it does not test that hypothesis," he said.
He is not suggesting this situation is comparable, but reminded me that at the time of Copernicus, the prevailing hypothesis was the sun revolved around the earth.
"The results of the USGS study are not necessarily correct in saying that carbon uptake by biomass might be greater than carbon loss from soils, but they do indicate that it is in within the realm of possibility that could happen," he said.
"I think where we are at now is that we have clarified some of the uncertainties with the USGS study, and the response of carbon uptake relative to carbon loss is one of those uncertainties that needs to be resolved."
Alaska makes up about 18 percent of the total land area of the United States, but the climate has been cold enough that more than half of the carbon stored in the ground in the country is beneath the state.
If temperatures continue to rise, as predicted, and permafrost thawing becomes widespread, much of that carbon could be released into the air, accelerating the pace of warming.
The warmer weather could accelerate a cycle in which more wildfires mean more thawing and the release of more carbon.
The environmental systems and their interaction are incredibly complicated and the information derived from climate models is built on assumptions about things that have yet to take place.
Think of the USGS study as one possible outcome of many.
Southeast forests are a vast carbon reserve, holding about 12.5 kilograms per square meter, nearly double the average for all U.S. forests. In addition, dead trees hold about 2.8 kilograms per square meter.
Permafrost scientist Vladimir Romanovsky of the UAF Geophysical Institute said it is possible increased plant growth in Alaska will change the carbon balance, but not necessarily.
He said USGS research should be treated with caution because the model may be wrong.
"The measurements are key here," he said. "If there will be some good measurements available for the next five or 10 years that would give more certainty as to where we're going."
"So far the thawing of permafrost is not that widespread, but it could start very soon," he said.
If permafrost begins to thaw on a widespread basis and there is not a large release of carbon, then the USGS report will probably be shown to right, but on the other hand a large release of carbon would contradict these predictions.
"Measurements are the way to reduce uncertainty," he said.
McGuire agrees: "We have to pull together more information to adequately test the responses of the models to changing environmental conditions associated with climate change."
Correction: This column has been edited to reflect that at the time of Copernicus, the prevailing hypothesis was that the sun revolved around the earth, not that the earth revolved around the sun.
Dermot Cole is a Fairbanks-based columnist. The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch News, which welcomes a broad range of viewpoints. To submit a piece for consideration, email commentary(at)alaskadispatch.com.