Climate change fallout irreversible

Many damaging effects of climate change are already basically irreversible, researchers declared Monday, warning that even if carbon emissions can somehow be halted temperatures around the globe will remain high until at least the year 3000.

“People have imagined that if we stopped emitting carbon dioxide the climate would go back to normal in 100 years, 200 years; that’s not true,” climate researcher Susan Solomon said.

Miss Solomon, of the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colo., is lead author of an international team’s paper reporting irreversible damage from climate change. The paper is being published in Tuesday’s edition of Proceedings of the National Academy of Sciences.

She defines “irreversible” as change that would remain for 1,000 years even if humans stopped adding carbon to the atmosphere immediately.

The findings were announced as President Obama ordered reviews that could lead to greater fuel efficiency and cleaner air, saying the Earth’s future depends on cutting air pollution.

Said Miss Solomon, “Climate change is slow, but it is unstoppable,” all the more reason to act quickly.

Alan Robock, of the Center for Environmental Prediction at Rutgers University, agreed with the report’s assessment. “It’s not like air pollution where if we turn off a smokestack, in a few days the air is clear,” said Mr. Robock, who was not part of Miss Solomon’s research team. “It means we have to try even harder to reduce emissions.”

Miss Solomon’s report “is quite important, not alarmist, and very important for the current debates on climate policy,” said Jonathan Overpeck, a climate researcher at the University of Arizona.

In her paper Miss Solomon, a leader of the International Panel on Climate Change and one of the world’s best known researchers on the subject, noted that temperatures around the globe have risen and changes in rainfall patterns have been observed in areas around the Mediterranean, southern Africa and southwestern North America.

Warmer climate also is causing expansion of the ocean, and that is expected to increase with the melting of ice on Greenland and Antarctica, the researchers said.

Global warming has been slowed by the ocean, Miss Solomon said, because water absorbs a lot of energy to warm up. But that good effect will not only wane over time, the ocean will help keep the planet warmer by giving off its accumulated heat to the air.

Climate change has been driven by gases in the atmosphere that trap heat from solar radiation and raise the planet’s temperature - the “greenhouse effect.” Carbon dioxide has been the most important of those gases because it remains in the air for hundreds of years. While other gases are responsible for nearly half of the warming, they degrade more rapidly, Miss Solomon said.