Last week the Department of Energy created a stir when it demonstrated a method for “drawing energy from ice” = tapping the methane hydrates that have long been known to be trapped in Arctic ice formations. The DOE said the vast reserves could form yet another “inexhaustible” source of natural gas.
Not so optimistic about hydrates was a paper featured on RealClearEnergy last week that consider the possibility that the release of this methane into the atmosphere could trigger a huge greenhouse gas episode that could hurl the earth back into the Paleocene-Eocene Thermal Maximum, one of the warmest periods in the history of the planet.
The graph above traces readings of carbon dioxide (CO2 - red) and methane (CH4 – green) in the atmosphere over the last 800,000 years. As you can see, they track very closely. As Al Gore illustrated in “An Inconvenient Truth,” the level of CO2 also tracks fairly closely the temperatures of the planet – periods of low CO2 concentration corresponding with ice ages and periods of high concentration with interglacial thaws. The speculation is that somehow the high levels of the two gases are interrelated and that one somehow serves as a “trigger” for the other. Since they both have a greenhouse effect, blocking the escape of infrared radiation from the earth’s surface, each gas may amplify any warming effect that the other is creating.
Hydrates are chemical formations where methane is bound to water molecules under extreme conditions of temperature or pressure. In a paper entitled “Methane, the Clathrate-gun conjecture and a disturbed Carbon Cycle,” Phil Harris explains the two main reservoirs of hydrates “There are two principal types of hydrate: Arctic hydrate, stabilized mainly by low temperatures in permafrost, on land and in the shallow Arctic Ocean, and marine hydrates stabilized mainly by pressure under sea water and some hundreds of meters of sediment.”
The most obvious speculation is that when the earth begins to warm form higher levels of carbon dioxide, this thaws Arctic ice, which releases the methane stored in hydrate formation into the atmosphere. “Methane is the third greenhouse gas, in order of importance [behind water vapor and carbon dioxide] but arguably the most likely to cause catastrophic change because the mass needed to change climate is small than for carbon dioxide, and the mass available is so large.”
Harris speculates that a “clathrate gun” – a sudden release of methane due to Arctic melting – could cause very sudden, uncontrollable changes in the earth’s climate. “The end of “Snowball Earth” [a completely frozen condition of the earth approximately 635 thousand years ago] is believed to have involved vast releases from methane hydrates,” he concludes.