8.7.2.4 Methane Hydrate Instability/Permafrost Methane

Methane hydrates are stored on the seabed along continental margins where they are stabilised by high pressures and low temperatures, implying that ocean warming may cause hydrate instability and release of methane into the atmosphere (see Section 4.7.2.4). Methane is also stored in the soils in areas of permafrost and warming increases the likelihood of a positive feedback in the climate system via permafrost melting and the release of trapped methane into the atmosphere. The likelihood of methane release from methane hydrates found in the oceans or methane trapped in permafrost layers is assessed in Chapter 7.

This subsection considers the potential usefulness of models in determining if those releases could trigger an abrupt climate change. Both forms of methane release represent a potential threshold in the climate system. As the climate warms, the likelihood of the system crossing a threshold for a sudden release increases (see Chapters 4, 7 and 10). Since these changes produce changes in the radiative forcing through changes in the greenhouse gas concentrations, the climatic impacts of such a release are the same as an increase in the rate of change in the radiative forcing. Therefore, the models’ ability to simulate any abrupt climate change should be similar to their ability to simulate future abrupt climate changes due to changes in the greenhouse gas forcing.