Sea-level rise triggered by global warming could spark a release of gas hydrate, triggering more global warming due to methane's ability to trap reflected heat in the atmosphere.

U.S. Geological Survey

Hot under the collar
These days, with global temperatures on a dangerous upward trend, discussions of energy resources can't ignore climate impacts. How might gas hydrates affect global warming due to greenhouse gases?

The discovery could reduce the already flagging demand for energy conservation since price, more than good intentions, is what reins in demand for energy.

Natural gas produces less carbon dioxide than either oil or coal, so substituting it may reduce greenhouse emissions.

That carbon might get released accidentally - with catastrophic results. Says Steven Holbrook: "The amount of organic carbon [meaning carbon bonded to hydrogen and perhaps other elements] in these deposits is ... by far the largest such reservoir on Earth, so it is vital to understand whether that reservoir is 'locked up' or whether it exchanges carbon with the oceans and atmosphere, either through gradual or catastrophic processes."

Perhaps most important: What is the fate of all that methane? Gram for gram, methane packs more greenhouse punch than carbon dioxide, so deliberate or accidental releases could accelerate global warming.

The other greenhouse gas
Methane has played a role in past climates: Holbrook writes a "huge amount of methane from hydrate was released in the Paleocene and contributed to (or caused?) the Late Paleocene Thermal Maximum (a warming period)."Obviously, until we know what triggered that warming, we won't know whether it might recur.

The picture is incomplete without considering the ongoing natural releases of methane from Earth – about which little is known. Published estimates of the annual releases range from 10¹¹ to 10¹⁴ grams, a thousand-fold range of uncertainty.

In fact, the real total is probably far higher, says Sassen, since the estimates are based on bacterial methane, not methane associated with petroleum. Worse, the estimates ignore the continental margins, where gas hydrate is found, because "production there is so uneven that the numbers get thrown out."

Nonetheless, at the rail of a ship above a gas vent in the Gulf of Mexico, it's obvious that a lot of gas is being released. "You can see the bubbles coming up," says Sassen.

Because this natural methane could be playing an unrecognized part in today's warming, more research into the source and transport of gas hydrates could fill in the picture of climatic change.

Help or hindrance?
One thing seems likely: Given the current shortages of fossil fuel and the reluctance to cut consumption, you are going to hear more about the tantalizingly huge supply of gas hydrates.

That's just as well, since fossil fuels don't last forever. On the continental shelf in the Gulf of Mexico, Sassen notes, "We started drilling in 1946, and in 1999, all of a sudden, more gas and oil is being produced in the continental slope in deep water than on the shelf. So we blew away the main, easy-to-find resource in the Gulf in 48 years. You can exploit and destroy an oil basin in just a few decades."

Yet Sassen sees a silver lining as rising prices pinch a nation addicted to cheap energy. "I think this little blip in price is reasonable and necessary. It will bring people closer to understanding what the real value of energy is."

Bibliographies.

©2000, University of Wisconsin, Board of Regents.