CROSSING A CLIMATE THRESHHOLD
Another Gas Attack
As ocean water warmed (arrow) methane molecules escaped from
Another idea, suggest Jerry Dickens and Jim O'Neil of the University of
Michigan, is that as the deep waters warmed from 11 degrees Celsius to 15 degrees
Celsius, they unleashed powerful greenhouse gases.
Large amounts of methane could have seeped up through the sediments into
the ocean, suggests Dickens, a graduate student in geochemistry. If the
methane escaped into the atmosphere, it could have caused significant
warming over tens to hundreds of years. That warming might have triggered
the release of even more methane, heating the climate out of control. But
until geologists figure out how to measure past levels of methane,
Dickens' idea will remain untested.
Today, methane is trapped in tiny pores between sand grains off
continental shores. Bacteria produce the methane as waste when they
consume organic matter. Cages of water molecules surround the methane gas,
making it a gray, ice-like solid called a hydrate. Could it melt?