Permafrost, ground that remains frozen for at least two consecutive years, covers around one-quarter of the land in the Northern Hemisphere. It contains approximately 1,700 billion tonnes of organic carbon, twice the amount currently in the atmosphere. If this carbon were to thaw and decompose due to climate change, it would release large amounts of carbon dioxide and methane, potent greenhouse gases that contribute to climate warming.

The potential consequences of permafrost thaw are far-reaching and difficult to predict. Permafrost thaw can:

- Destabilize infrastructure such as roads, railways, pipelines, and buildings built on frozen ground.

- Alter landscapes by creating new lakes, wetlands, and rivers, and increasing the risk of flooding and landslides.

- Release large amounts of greenhouse gases, contributing to further warming and climate change.

- Reduce the amount of freshwater available for drinking, irrigation, and hydropower, as permafrost acts as a natural reservoir for water.

- Disrupt ecosystems by altering the habitat for plants and animals, particularly in the Arctic where many species are adapted to cold conditions.

Permafrost thaw could also have significant global impacts. The release of greenhouse gases could accelerate climate change, leading to more extreme weather events, rising sea levels, and widespread disruption to ecosystems. It could also impact agriculture and food security, as well as trigger migration and conflict as people are displaced from their homes due to environmental changes.