55 million years ago, a massive blast of gas drove up Earth's temperature 7C. And another explosion is on the cards, say experts By David Keys 16 June 2001 A period of ecological and evolutionary chaos 55 million years ago, caused by a release from the earth of 2,000 billion tons of methane gas, has been discovered by scientists who fear a repeat could cause a devastating acceleration in global warming.
The new research, revealed this Sunday evening in a Channel 4 documentary The Day the Oceans Boiled, suggests that methane releases helped drive up temperatures by seven degrees centigrade in many parts of the world.
Now some scientists fear a series of massive methane emissions, triggered by the man-made global warming, could propel earth's ecological systems towards catastrophe. A prolonged series of large releases of the gas could push up temperatures rapidly and trigger long-term further warming processes capable of melting a substantial part of Earth's polar ice, raising sea levels world-wide by up to two metres.
"It is the first time geology has isolated an individual methane release event in the distant past," said Santo Bains of Oxford University's department of earth sciences. "Now we can see just how it played its part in the global warming process of that era."
Professor Bains led geologists in three years of research through the badlands of Wyoming and on samples from the seabeds off Florida and Antarctica.
The team study confirms work by Russian, French and US scientists using "fossil" air bubbles in Greenland and Antarctic ice-cores. That shows global warming at the end of the last Ice Age 14,000 years ago was also associated with a huge and very rapid increase in methane in the atmosphere.
Methane causes far more damage to the ozone layer than CO2, the more well-known villain of global warming. And massive quantities of methane are trapped in and below the permafrost in the Arctic.
As global warming melts the more southerly parts of the previously frozen sub-soil, frozen gas-water compounds (methane hydrates) and methane gas will escape into the atmosphere, driving global temperatures up even further.
As global warming raises sea levels, large areas of more northerly Siberian and other permafrost areas will be flooded and thus, in relative terms, warmed. This would allow release of yet more methane.
Second, beneath continental shelf seabeds worldwide are vast quantities of methane hydrates in sediments with methane gas trapped below them. Cold temperatures keep them stable as well as pressure, mainly from the overburden of geological sediments and the water on top which prevents destabilisation.
Although ocean warming will gradually warm under-sea sediments and slowly release deeply buried methane, the major natural occasions on which methane can escape on a rapid and massive scale from these buried reserves is when underwater landslides expose previously buried gas-bearing sediments, thus reducing pressure in an instant.
And a new factor, only now beginning to be appreciated by climate scientists, is that global warming could potentially increase the rate of these marine landslides. Because global warming creates a predominantly warmer and wetter world in which erratic floods are likely to occur, many river volume flows will probably increase, bringing with them more riverine erosion.
Increased river flow, coupled with the consequent increase in the expanse of wetland areas, will also create a third mechanism for increasing natural methane emissions, this time by creating larger expanses of methane-producing swamps.
Methane is likely to be much more important than previously thought, says palaeo-climatologist Professor Euan Nisbet, of Royal Holloway College, University of London.
"The new evidence clearly shows methane was deeply involved in the very rapid global warming at the end of the Ice Age," he says. "By studying that event, we may well be able to understand the effect of future global warming on the Arctic."
But there is another major factor, so far unappreciated by most climate scientists, which has also been left out of nearly all global warming predictive calculations. Although most areas of the world will become wetter as global warming progresses, one key area, the Amazon Basin, could well become drier, shows a British Meteorological Office study. As a result, the forest would be unable to survive and would begin to die. This would accelerate global warming in two ways. First, as the jungle dries, it would become flammable and vulnerable to massive lightning- triggered forest fires. This would release up to 150 billion tons of CO2 into the atmosphere.
Second, the destruction of the forest and its replacement by savannah would reduce the planet's ability to absorb CO2 more profoundly than scientists had realised.
Four Brazilian biologists, led by Dr Antonio Nobre of Brazil's National Institute for the Study of the Amazon, have made the surprising discovery that the Amazon jungle has been substantially increasing its biomass in response to human CO2 emissions.
In other words, the Amazon is reducing the rate of global warming's acceleration much more than science has hitherto believed. So if the jungle disappears and climatologists warn that could occur between the years 2050 and 2100 its disappearance would have an even more detrimental effect than previously thought.