A new study, published in the journal Nature Climate Change, suggests that the global warming already anticipated by scientists could thaw much more permafrost than previously expected. Permafrost is frozen land that accounts for six million square miles of the earth. The new study shows that each degree Celsius of warming could thaw as much as 1.5 million square miles of permafrost. That number is about 20 percent higher than has been predicted by prior studies, according to Sarah E. Chadburn, University of Leeds researcher and lead author of the study.

“Previous estimates of global changes in permafrost were done using climate models. Our approach is more based on using historical observations and extrapolating that to the future. It’s a very simple approach,” said Chadburn.

Though permafrost thaws gradually, it has already caused problems for roads, building foundations, and other infrastructure in areas with permafrost, such as Northern Alaska or Siberia. In a vicious cycle, the thawing also contributes to climate change, as organic matter decomposes as it warms, it emits greenhouse gases into the atmosphere.

Chadburn and other researchers sought to find out how permafrost would be affected if the world were to meet the targets of the 2015 Paris climate agreement, keeping temperature increases to 1.5 degrees Celsius or less. That goal was widely considered ambitious. The researchers found that an increase of two degrees – just over the Paris target – would cause about 2.5 million square miles of permafrost to thaw, based on a 1960 to 1990 baseline. That amount comprises about 40 percent of the world’s total. Meeting the Paris targets would reduce that by 30 percent, according to the report.

If both those targets are missed, the report showed that the consequences could be disastrous. Increases of 5 degrees Celsius would leave only 20 percent of the world’s total of permafrost.

According to permafrost expert Edward A. G. Schuur from Northern Arizona University, the report is “an important and interesting calculation of where permafrost will be at some distant point in the future as we undergo climate warming.”

“What’s really important is this is based on totally different assumptions. It’s useful because it gives us a different perspective,” he added.

Schuur also said that such a loss of permafrost would have a vast impact on the world, and especially on the people who live in areas with permafrost.

According to Schuur:

“There will be surface changes that affect everyone who lives there. I don’t think there’s any place in the permafrost zone that’s remote enough to escape changes.”

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