Juliet Eilperin of the Washington Post discusses the Debate on Climate Shifts to Issue of Irreparable Change:
Some Experts on Global Warming Foresee 'Tipping Point' When It Is Too Late to Act
Now that most scientists agree human activity is causing Earth to warm, the central debate has shifted to whether climate change is progressing so rapidly that, within decades, humans may be helpless to slow or reverse the trend.
This "tipping point" scenario has begun to consume many prominent researchers in the United States and abroad, because the answer could determine how drastically countries need to reduce their greenhouse gas emissions in the coming years. While scientists remain uncertain when such a point might occur, many say it is urgent that policymakers cut global carbon dioxide emissions in half over the next 50 years or risk the triggering of changes that would be irreversible.
There are three specific events that these scientists describe as especially worrisome and potentially imminent, although the time frames are a matter of dispute: widespread coral bleaching that could damage the world's fisheries within three decades; dramatic sea level rise by the end of the century that would take tens of thousands of years to reverse; and, within 200 years, a shutdown of the ocean current that moderates temperatures in northern Europe.
The debate has been intensifying because Earth is warming much faster than some researchers had predicted. James E. Hansen, who directs NASA's Goddard Institute of Space Studies, last week confirmed that 2005 was the warmest year on record, surpassing 1998. Earth's average temperature has risen nearly 1 degree Fahrenheit over the past 30 years, he noted, and another increase of about 4 degrees over the next century would "imply changes that constitute practically a different planet."
"It's not something you can adapt to," Hansen said in an interview. "We can't let it go on another 10 years like this. We've got to do something."
Ian Johnston, writing for Scotsman.com Nightmare vision of a world 200 years on:
ONE of Britain's leading environmentalists will today sound a doomsday warning to the world: humanity's very existence is under threat from climate change and, even if we survive, the population will crash to about a third of its current level.From the BBC we have Sea level rise 'is accelerating'
Sir Crispin Tickell, the man who convinced former prime minister Margaret Thatcher that global warming was a real problem, predicts that, in 200 years, there could be as few as 2.3 billion people because rising sea levels and temperatures will make some areas uninhabitable and, coupled with social factors, depress birth rates.
But he also says our survival is "not guaranteed" and that the presence of humans on the planet could be "no more than a somewhat messy episode in the history of the Earth".
"The human impact on the Earth has slowly and then rapidly increased, most of all in the last 250 years.
"The resulting transformation of the environment is unsustainable. The main factors are human population increase, degradation of land, consumption of resources, water pollution and supply, climate change, destruction of other species ...
"Most of the solutions to the problems we have created, including the widening division between rich and poor, are well known but few want to confront them, singly or together. To do so we have to rethink our value system."
He pointed to recent droughts in Mediterranean countries and the increasing severity of hurricanes in the Caribbean - caused by a rise in sea temperature - as some of the signs that global warming is starting to get out of hand.
Global sea levels could rise by about 30cm during this century if current trends continue, a study warns.Read more about the Intergovernmental Panel on Climate Change Third Assessment Report.
Australian researchers found that sea levels rose by 19.5cm between 1870 and 2004, with accelerated rates in the final 50 years of that period.
The research, published in the journal Geophysical Research Letters, used data from tide gauges around the world.
The findings fit within predictions made by the Intergovernmental Panel on Climate Change (IPCC).
The IPCC's Third Assessment Report, published in 2001, projected that the global average sea level would rise by between 9 and 88cm between 1990 and 2100.
If the acceleration continues at the current rate, the scientists warn that sea levels could rise during this century by between 28 and 34cm.
Dr John Church, a scientist with the Commonwealth Scientific and Industrial Research Organisation based in Tasmania and an author of the study, said that higher sea levels could have grave effects on some areas.
"It means there will be increased flooding of low-lying areas when there are storm surges," he told the Associated Press.
"It means increased coastal erosion on sandy beaches; we're going to see increased flooding on island nations."