Methane hydrates, which are formations of methane gas molecules enclosed in ‘cages’ of water ice, represent an enormous reservoir of fossil carbon. Although the magnitude of this reservoir is still highly uncertain, it is widely believed to contain thousands of giga-tonnes of carbon (GtC). To put that in perspective, the Earth’s atmosphere currently contains about 800 GtC as CO2, of which about 180 GtC and 40 GtC were added through human burning of fossil fuels and biomass, respectively. This anthropogenic addition of CO2 has been the dominant cause of the observed global warming since the industrial era, and it is now apparent that continuing on the current emissions trajectory would result in disastrous climate-related impacts.
These basic facts, along with the well-established fact that a significant fraction of anthropogenic CO2 emissions will remain in the atmosphere for many centuries, make it abundantly clear that widespread extraction and use of even a seemingly small fraction of the world’s methane hydrates would be extremely undesirable from a global climate perspective, if such use results in further unconstrained emissions of CO2 (or methane).
Thus, the recent buzz about Japan’s methane hydrate exploration is certainly cause for concern. However, in the interest of basic fairness and avoidance of premature finger-pointing, it should be noted that my own country’s government has made no secret of its plans to make methane hydrates a commercially viable fuel source within the next decade, see reference.
Whether or not this is a feasible goal remains to be seen. However, given the worldwide dependence on fossil fuels, the impending ‘peaks’ in global conventional oil and natural gas production, and the massive fuel potential of hydrates, it seems very likely that more and more countries (and energy companies) will be tempted to pursue similar goals as the American and Japanese governments (e.g., see reference).
Several recent studies by James Hansen, myself, and our colleagues have concluded that unconventional fossil fuels such as methane hydrates can only be burned if the resulting greenhouse gases are prevented from entering the atmosphere (see Implications of "peak oil" for atmospheric CO2 and climate and Target atmospheric CO2: Where should humanity aim?). A major concern is that fuel derived from methane hydrates would most likely be used to substitute for dwindling oil and gas. But since most CO2 emissions from current oil and gas use are not amenable to capture and sequestration (because these fuels are used mainly in vehicles, homes, etc.), any hydrate-derived fuels must be used differently in the future. One possible way to resolve this would be to use these fuels only at power plants that employ carbon capture and sequestration, with the resulting electricity being used to power plug-in hybrid cars.
In a broader sense though, the pursuit of methane hydrates as fuels seems like a step backward, since it would only entail continuing reliance on finite, nonrenewable fossil energy. Given that the world must inevitably move beyond such resources, it would make far more sense to focus near-term efforts on large-scale development of truly ‘green’, carbon-negative technologies.
Pushker Kharecha, Climate Scientist, NASA Goddard Institute for Space Studies/Columbia University Earth Institute