For tens of thousands of years, huge amounts of plant matter—roots, leaf fragments and the like—have been kept in cold storage underground in the northern parts of Alaska, Canada, Europe and Siberia. They're embedded in permafrost, or permanently frozen soil. Even when the top few inches of ground thaw out in the Arctic summer, permafrost never does. As the planet continues to warm, however, the "perma" in permafrost is looking less eternal. Scientist have known for years, in fact, that rising temperatures threaten to thaw the permafrost, allowing the plant material to decompose and release carbon dioxide (CO2) into the atmosphere, boosting the effects of CO2 from the burning of fossil fuels.
What they have never known is just how much of that deep-frozen CO2 is likely to emerge. Now, a study in the journal Tellus has provided an answer: by 2200, the extra CO2 could add up to about half as much (allowing for uncertainties) as we've produced through fossil-fuel burning since the dawn of the Industrial Revolution. I talked to the lead author, Kevin Schaefer, about what they learned.