At present, Arctic land areas are slowly absorbing carbon dioxide from the atmosphere and preserving it in plant tissues that gradually become peat or part of the soil. This has been happening for thousands of years. Around 44% of the world's near surface soil carbon is stored in Arctic soils - about twice as much carbon as in the entire Earth's atmosphere. If the permafrost thaws on a large scale this century or later, a substantial amount of this soil carbon will be converted to carbon dioxide, potentially increasing the amount of carbon dioxide in the atmosphere. This process could override the gradual storage of carbon due to plant growth on land and algal growth in water.