Methane powered runaway global warming - 55m/yrs ago

Methane released from wetlands turned the Earth into a hothouse 55 million years ago, according to research released Wednesday that could shed light on a worrying aspect of today's climate-change crisis.

Scientists have long sought to understand the triggers for an extraordinary warming episode called the Palaeocene-Eocene Thermal Maximum (PETM), which occurred about 10 million years after the twilight of the dinosaurs.

Earth's surface warmed by at least five degrees Celsius (nine degrees Fahrenheit) in just a few hundred or a few thousand years. The Arctic Ocean was at 23 degrees Celsius (73 degrees Fahrenheit) -- about the same as a tepid bath -- before the planet eventually cooled.

Richard Pancost, a researcher at Britain's University of Bristol, seized an opportunity to dig, literally, into this mystery.

Excavation of a site in southeast England to set down the Channel Tunnel rail link exposed layers of sediment from a bog that had existed at the time of the PETM.

Pancost's team sifted through the dirt to measure the carbon isotope values of hopanoids, which are compounds made by bacteria.

They found that levels of these isotopes suddenly fell at the onset of the PETM, yielding a signature that can only be explained if the bugs dramatically switched to a diet of methane, a powerful, naturally-occurring greenhouse gas.

Reporting in the British journal Nature, Pancost believes that the methane had remained locked up in the soil for millions of years before warming released it into the atmosphere.

As atmospheric methane levels rose, so too did Earth's temperature as a result of the famous "greenhouse" effect. In turn, that released more methane, and so on.

In other words, it was a vicious circle (a "positive feedback" in scientific parlance), in which warming begat warming.

The study has relevance because of the gigatonnes of methane locked in the Siberian permafrost today.

With the permafrost slowly retreating as a result of global warming, some experts fear a threshold whereby this huge stock of greenhouse gas may also be released, unleashing unstoppable climate change.

But the temperature at which this could happen is unknown and the mechanisms by which the methane is released are unclear.


Meanwhile - "Dinosaur find shows early social behavior"

The fossilized remains of six young dinosaurs found together in a "nursery" at a site in China show these animals had started forming social groups much earlier than previously thought, scientists said on Thursday.

The find sheds light on the life of the beaked dinosaur Psittacosaurus and on the origins of social behavior in its descendents, including the horned Triceratops, said Paul Barrett, a paleontologist at Britain's Natural History Museum, who led the study...

Psittacosaurus was a small herbivore that lived in China, Mongolia, Siberia and Thailand about 130 million to 100 million years ago. It was an early relative of Triceratops and Protoceratops.

The largest of the young dinosaurs, probably aged one-and-a-half to three-years old when they died, measured about 50 centimeters (1.6 feet) from the tip of the nose to its tail and weighed about a kilogram (2 lbs). Adults were about 2 meters long and weighed up to 30 kilograms.

The age range of the fossils suggested they came from different eggs, laid by different parents, he said. The remains formed a nursery with babies from at least two different parents, he added.

The baby dinosaurs were probably killed in a volcanic mudflow, but the way the researchers discovered them, lying side by side, indicates they lived in a herd, Barrett said.

"These animals had left the nest and were already hanging out with each other," he said.