On the closing day of the Congress on Climate Change held last week in Copenhagen, one of the world's leading experts, Hans Joachim Schellnhuber, the director of the Potsdam Institute for Climate Impact Research in Germany, said that if the buildup of greenhouse gases and its consequences pushed global temperatures 9 degrees Fahrenheit higher than today — well below the upper temperature range that scientists project could occur from global warming — Earth’s population would be devastated.
“In a very cynical way, it’s a triumph for science because at last we have stabilized something –- namely the estimates for the carrying capacity of the planet, namely below 1 billion people."
Schellnhuber's comments at the Copenhagen conference underscore that, given high rates of observed emissions, the worst-case IPCC scenario trajectories are unfoldinmg. For many key parameters, the climate system is already moving beyond the patterns of natural variability within which our society and economy have developed and thrived. These parameters include global mean surface temperature, sea-level rise, ocean and ice sheet dynamics, ocean acidification, and extreme climatic events. There is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts.
Recent observations show that societies are highly vulnerable to even modest levels of climate change, with poor nations and communities particularly at risk. Temperature rises above 2°C will be very difficult for contemporary societies to cope with, and will increase the level of climate disruption through the rest of the century.
It is important for people to understand that the warming the IPCC talks about is not hypothetical. Eleven of the last 12 years (1995-2006) rank among the warmest years in global surface temperature since 1850. Glaciers and snow cover have declined, and ice sheets from Greenland and parts of Antarctica are melting. The ocean has been absorbing more than 80% of the heat added to the climate system, yet the average temperature of the ocean has increased up to a depth of 3,000 meters, causing seawater to expand and contributing to sea level rise.
Schellnhuber, citing his own research, said that at certain “tipping points,” higher temperatures could cause areas of the ocean to become deoxygenated, resulting in what he calls “oxygen holes” between 600 and 2,400 feet deep. These are areas so depleted of the gas that they would badly disrupt the food chain.
Unabated warming would also lead to “disruption of the monsoon, collapse of the Amazon rain forest and the Greenland ice sheet will meltdown,” he said.
Scientists must make clear the disastrous effects of climate change so the world takes action now to cut carbon emissions, leading economist Nicholas Stern said on told the gathering of 2,000 scientists.
"You have to tell people very clearly and strongly just how difficult (a temperature rise of) four, five, six or seven degrees Celsius is," he said.
"Billions of people would have to move and there would be very severe conflict," said Stern, a professor at the London School of Economics and a former British Treasury economist.
"That's a story that must be told to persuade people it's a very bad idea to go anywhere near five degrees. This is not a black swan, this is a big probability of a devastating outcome," he
Posted by Casey Kazan