Permafrost is beginning to melt under the influence of climate change across parts of Siberia, Canada and Alaska in a trend that threatens homes, railways and oil pipelines, according to a new U.N. report.

The accelerating melt is also poised to free vast amounts of carbon dioxide and methane that have been trapped in the ground for thousands of years, the U.N. Environment Program (UNEP) report cautions.

It was released at the U.N. climate talks being held in Qatar. The amount of greenhouse gases ready to seep out of the melting permafrost between now and 2100 could equal nearly 40 percent of annual emissions from human sources, the report says.

“Permafrost is one of the keys to the planet's future because it contains large stores of frozen organic matter that, if thawed and released into the atmosphere, would amplify current global warming and propel us to a warmer world,” U.N. Undersecretary General and UNEP Executive Director Achim Steiner said.

The thaw also threatens to undermine such infrastructure as bridges, roads, oil pipelines and power lines in Arctic regions.

Graph: National Snow & Ice Data Center