While scientists who study climate overwhelmingly agree that human activities bear a large responsibility for global warming, two recent analyses have identified a surprising partner in the effect: Mother Nature herself. The analyses, which synthesize the results of 76 separate research projects, indicate that organic matter stored in the soil is releasing the greenhouse gases carbon dioxide and methane into the atmosphere at an increasing rate as the climate warms up. 

Source: Human-Caused Climate Change has a Partner in Crime: Mother Nature Herself | Inside Science