Maps, produced by ESA’s Climate Change Initiative, are providing new insights into the Arctic's thawing permafrost, which plays an important role in the global climate and is also one of the components of the Earth system most sensitive to global warming.

According to the latest Intergovernmental Panel on Climate Change Special Report, permafrost temperatures have increased to record high levels from the 1980s to present. As a consequence, concern is growing that significant amounts of greenhouse gases could be mobilised over the coming decades as it thaws, and potentially amplify climate change.

Permafrost is any ground that remains completely frozen for at least two consecutive years – these permanently frozen grounds are most common in high latitude regions such as Alaska and Siberia, or at high altitudes like the Andes and Himalayas.

Near the surface, Arctic permafrost soils contain large quantities of organic carbon and materials leftover from dead plants that cannot decompose or rot, whereas permafrost layers deeper down contain soils made of minerals. When permafrost thaws, it releases methane and carbon dioxide – adding these greenhouse gases to the atmosphere.

Since permafrost is a subsurface phenomenon, understanding it is challenging without relying strictly on in situ measurements. Satellite sensors cannot measure permafrost directly, but a dedicated project as part of ESA’s Climate Change Initiative (CCI), has used complementary satellite measurements of landscape features such as land-surface temperature and land cover to estimate permafrost extent.