Climate Central: Nearly a quarter of the Northern Hemisphere's land surface is covered in permanently frozen soil, or permafrost, which is filled with carbon-rich plant debris -- enough to double the amount of heat-trapping carbon in the atmosphere if the permafrost all melted and the organic matter decomposed.
According to a paper published Thursday in Science, that melting could come sooner, and be more widespread, than experts previously believed. If global average temperature were to rise another 2.5°F (1.5°C),...