Warning that alpine permafrost 'may accelerate global warming'

Alpine permafrost is set to melt faster as a result of global warming, in turn releasing greenhouse gases and causing world temperatures to rise more quickly, scientists have warned.

Up to 60% of permafrost could melt in Alpine areas, posing serious challenges in the battle against climate change, researchers said.

Globally, permafrost contains 1,500 trillion grams of carbon – twice the carbon currently in the atmosphere, and triple the amount emitted by human activity since 1850.

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Alpine permafrost, which contains 85 trillion grams of carbon, is expected to melt at a faster rate than arctic permafrost under current global warming conditions, according to research published in Nature Communications.

This may contribute even more to rising global temperatures.

Scientists believe that Earth’s future will look similar to the mid-Pliocene warm period – an epoch 3.3 million to 3 million years ago when the average air temperature at mid-latitudes rarely dropped below freezing.

Co-author Carmala Garzione, dean of the University of Arizona College of Science, said: "Atmospheric carbon dioxide concentrations today are similar, or maybe even higher, than the mid-Pliocene because of the burning of fossil fuels, and so scientists point at that time period as an analog for our current and near-future climate.

"We're not feeling the full effects of the rise in atmospheric carbon dioxide yet because our Earth system takes time to adjust."

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Feng Cheng, the paper's lead author and a professor at Peking University in China, said: "We wanted to estimate the stability of modern permafrost globally in a warmer-than-today climate scenario.

"Our findings were very surprising and highlight the fact that we need to put more effort into monitoring the stability of the permafrost in the alpine region."

The team used carbonate – a family of minerals that formed in a Tibetan Plateau lake to estimate temperatures during the Pliocene period (5.3 to 2.6 million years ago) and the Pleistocene period (between 2.6 million and 11,700 years ago).

When algae grows in lakes, it absorbs carbon dioxide from the water and, as a result, decreases lake acidity.

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That decrease drives the lake to form finely-grained carbonate minerals that settle at the lake bottom.

The atoms in that carbonate reflect the temperature at which the carbonate formed, and can be used like a time-travelling thermometer.

Ultimately, the modelling suggests that under current levels of atmospheric carbon dioxide, 20% of arctic permafrost land area and 60% of alpine permafrost land area will be lost in the future.

High-altitude alpine regions are more sensitive than high-latitude arctic regions to warming under higher atmospheric carbon dioxide conditions.

"The Pliocene is an important period as an ancient analogue for how Earth will adjust to the carbon dioxide that humans have already released to the atmosphere," Garzione said.

"We need better and broader studies of the vulnerability of alpine regions under global warming scenarios. There's been a lot of focus on the stability of arctic permafrost, because it covers more land area and contains a huge reservoir of organic carbon trapped in permafrost, but we also need to be aware that alpine regions stand to lose more permafrost proportionally and are important in understanding of potential carbon release under global warming scenarios."

Previous research suggested that thawing permafrost could create a dangerous ‘feedback’ in global warming by releasing greenhouse gases.

The feedback mechanism, combined with the loss of heat-reflecting white ice, could increase global warming by 5%, reports suggested.