Methane emissions due to human-related activities, shown to the right of the volcano, account for approximately 70 per cent of the total emissions (Reeburgh 2007; Colwell and Ussler III 2010). Gas Hydrates are currently estimated to contribute about 5 Tg (Tg = 1012 grammes) of methane (3.5 Tg carbon) per year to the atmosphere (IPCC, 2007). Emission rates for gas hydrates are highly speculative, however, and may overestimate the atmospheric methane contribution by not fully accounting for methane consumed by microbes in the sediment and water column. Additional research will be required to constrain the methane flux from gas hydrates that reaches the atmosphere.
From collection: Frozen Heat - A Global Outlook on Methane Gas Hydrates