An important climate feedback scientists have long warned about is apparently becoming a reality: 30 percent of Arctic soils are no longer carbon sinks, but release more CO2 than they store. This is the result of a comprehensive study published in Nature Climate Change. This is due to rising temperatures, which sometimes cause permafrost soils to thaw, releasing any carbon stored in them. In addition, wildfires are becoming more frequent; if they are factored in, 40 percent of the Arctic is already a carbon source.