Permafrost, or ground that is frozen for two or more years, stretches over about 14 million square kilometers in the Northern Hemisphere, 15% of the hemisphere's land area. Cold temperatures limit the decomposition of organic material, making permafrost soils a significant carbon sink. But warming temperatures from climate change are thawing permafrost and allowing microbes to decompose stored carbon. The result is a release of greenhouse gases, creating a feedback loop that further drives warming climate conditions.