Effect on Global Climate

When methane is released into the atmosphere, it acts as a greenhouse gas just like carbon dioxide, but 30 times more effective. Therefore, it is a relevant factor in global warming of the atmosphere. Although the atmosphere stores as much as 760 gigatons of CO2, a release of methane from an estimated 10,000 gigatons of gas hydrate deposits could alter its properties to a great extent. An increased release of methane from gas hydrate could affect the glacial/interglacial cycle. A positive feedback would be caused by permafrost gas hydrate on land due to its temperature sensitivity, whereas oceanic gas hydrate would cause a negative feedback as it is controlled by sea level changes.

In case of fast destabilization, methane liberated from gas hydrates becomes an important agent of climate change. However, the time scales of related processes are not fully understood, so far. Compared to atmospheric methane, methane stored in gas hydrate may be enriched in the stable carbon isotope 12C, which can be used as a tracer. Results from paleoclimate research indicate that sudden changes in the isotopic composition of inorganic carbon dissolved in oceanic waters about 55 my ago as well as in the most recent climate record may be explained by methane release from marine hydrate deposits. First modelling results show how a methane peak triggered by the decomposition of one gigaton of gas hydrate may affect the atmospheric and oceanic 13C/12C budgets for 20,000 years. This could be a first approach to explain the global 12C anomaly which has been found to have occurred 55 my ago.