Now to the methane. No one expects that there will be methane
erupting everywhere. Hydrates are stable only within a narrow pressure/temperature range. When temperature crosses that stable point, then methane is emitted. Where this is happening is in the arctic. Raising the deep ocean temperature to the point where say all the hydrates on the NZ shelf outgas is an Armageddon scenario which fortunately doesnt seem likely (though my work does have people working in this area – its an active research area because hydrates are potentially a menace but also a possible resource. As a caution, it wasnt that long ago, that my colleagues were discussing whether methane from hydrates could make it to the surface without oxidizing (as CO2 the carbon is a lot safer than as CH4. Clearly it can so the risk assessment has gone up.)