Methane would warm the planet.

    Riverside, California - Global warming could release long-dormant stores of methane gas trapped beneath the Arctic permafrost, causing an abrupt and catastrophic climate change like one that occurred 635 million years ago, University of California-Riverside researchers have determined.

    Back then, the sheets of ice that covered Earth started to collapse, releasing methane gas that warmed the planet and caused the ice to retreat over a period of 100 to 1,000 years, said Martin Kennedy, a geology professor in UCR's Department of Earth Sciences. Kennedy led the research team.

    "It was the greatest global-warming event of Earth's history almost certainly," he said.

    The findings are published in the latest issue of Nature. They suggest that methane ice sheets still exist beneath Arctic ice sheets that are being degraded by rising carbon-dioxide levels in Earth's atmosphere.

    Recent research indicates that the ice sheets are melting and methane gas is being released at a much higher rate than previously thought, he said.

    "It doesn't make one feel a lot better about the future," Kennedy said.

    If a similar phenomenon occurred today, the most noticeable change would be a rise in sea level, he said. If the Greenland ice sheet collapsed, the sea level would rise about 20 feet, inundating major coastal cities. Accompanying drought could lead to crop failures and widespread famine, he said.

    Mary Droser, chairwoman of UCR's department of earth sciences, said the world spends a lot of time and energy worrying about global climate change, and this is an example of an abrupt change through a process that could repeat itself today. "He has done an exquisite job of documenting this," Droser said. "It's really an elegant piece of work."

    Kennedy said computer models cannot predict nor explain past climate changes. Those answers are available only by studying past geologic records, which is what Kennedy and his colleagues are doing.

    They analyzed hundreds of marine sediment samples from South Australia looking for stable isotopes, a tool used in climate reconstruction. They found the greatest variation of the oxygen isotope ever reported from marine sediments, which they attributed to the melting ice sheets and methane gas release.

    The next step will be to try to estimate how much of that temperature change was due solely to methane, a greenhouse gas that reacts with oxygen to form carbon dioxide.

    One of the more controversial findings of Kennedy's research is that the abrupt change 635 million years ago immediately preceded the appearance of multicelled animals in fossil records.

    "Animals evolved after the whole system stabilized, and we're suggesting there's a linkage there," he said.

    Kennedy directs the Global Climate and Environmental Change Graduate Program at UCR. His team includes UCR graduate student David Mrofka and Chris von der borch of Flinders University in Australia. The study was supported by grants from the National Science Foundation and NASA Exobiology.