Evidence is growing that global warming is already starting to disrupt the world's delicately-balanced climate system, and the damage will reverberate for generations, a top science conference was told.
"There is no longer any doubt that the Earth's climate is changing," conference chairman Dennis Tirpak said Tuesday.
"Globally, nine of the past 10 years have been the warmest since records began in 1861," he said. "Rising greenhouse gases are affecting rainfall patterns and the global water cycle."
Tirpak singled out the heatwave that gripped western Europe in 2003 as an example. Europe's worst natural disaster in 50 years killed as many as 30,000 people and inflicted an estimated 30 billion dollars (23 billion euros) in damage.
"Since the 1970s, climatic warming has increased the extent and frequency of droughts over land," he said. "(...) Terrestrial ecological systems are shifting and marine systems are changing, all with outcomes that are difficult to predict."
In temperate parts of Asia, "recurring incidence of floods and droughts is already apparent," said Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change (IPCC), the UN's paramount scientific authority on global warming.
British scientist Chris Rapley said melting ice from Antarctica was already accounting for at least 15 percent of the two-millimeter annual rise (0.06 inches) in the global sea level due to warming.
In the Antarctic peninsula, which juts north from the continent, there had been three iceshelf breakups in the last 10 years, including the creation of the Larsen B iceberg, a Luxembourg-sized behemoth that is the biggest floating object in the world.
When these iceshelves break off, that speeds up the flow of ice into the sea from coastal glaciers, he said. The ice melted, adding to global sea levels, he said.
"It's like a cork in a bottle," he said. "You remove the icesheet and the glacial flow increases," he said.
If Antarctica melted, that would boost global sea levels by some 120 meters (390 feet), if past evidence from Earth's natural cycle of ice ages is a guide.
However, most of Antarctica's ice is locked up in the Western Antarctica icesheet, and temperatures there are somewhat cooler than before, said Rapley.
The conference, hosted by Britain at its Met Office headquarters in this southwestern English city, is tasked with coming up with a state-of-play assessment about man-made global warming.
The phenomenon is blamed on the unbridled burning of gas, coal and oil, the fuels that powered industrialization.
They release into the atmosphere carbon dioxide (CO2) and other gases that have been locked in Earth's crust for millions of years.
This carbon pollution traps the Sun, causing Earth's surface to heat, disrupting the ballet-like interplay between three physical giants: sea, air and land.
One problem is that even if pollution were slashed immediately, temperatures would continue to rise because of the gas which has already been spewed into the atmosphere.
"The inertia can carry the impacts, especially on sea level rise, for centuries, if not for millennia," Pachauri said.
Sea levels rise mainly because water expands as it is heated. The oceans are such vast volumes of water that, once the warming starts, it takes a long time for the process to stop.
That warning was underscored by a study about the risk of a meltdown of the Greenland icesheet, something that would raise global sea levels by seven meters (22.75 feet) if it were lost completely.
The icesheet could start to contract when local temperatures warm by more than 2.7 C (4.8 F) compared with the present.
"There is a significant possibility that this trigger point will be reached in the next few centuries," said Jason Lowe of Britain's Hadley Center for Climate Prediction and Research.
Even if atmospheric CO2 levels are eventually stabilized at quite modest concentrations, sea levels will continue to rise "for more than 1,000 years," he said. "Deglaciation of Greenland may be irreversible."
Copyright 2005 AFP