Hard-to-predict sudden changes to Earth's environment are more worrisome than climate change's bigger but more gradual impacts, a panel of scientists advising the US government has concluded.
The 200-page report by the National Academy of Sciences, released on Tuesday, looked at warming problems that can occur in years instead of centuries. The report repeatedly warns of potential "tipping points" where the climate passes thresholds, beyond which "major and rapid changes occur." And some of these quick changes are happening now, said study chairman James White of the University of Colorado.
The report says abrupt changes like melting ice in the Arctic Ocean and mass species extinctions have already started and are worse than predicted. It says thousands of species are changing their ranges, seasonal patterns or in some cases are going extinct because of human-caused climate change. Species in danger include some coral; pika, a rabbit-like creature; the Hawaiian silversword plant and polar bears.
At the bottom of the world in Antarctica, the melting ice in the west could be more of a wild card than originally thought. If the massive ice sheet melts it may happen relatively rapidly and could raise world sea levels by 13 feet, but researchers aren't certain how soon that may occur.
However, the report also had what researchers called "good news." It said two other abrupt climate threats that worried researchers likely won't be so sudden, giving people more time to prepare and adapt.
Those two less-imminent threats are giant burps of undersea and frozen methane, a super-potent greenhouse gas, and the slowing of deep ocean currents. That slowdown is a scenario that would oddly lead to dramatic coastal cooling and was featured in the 2004 movie The Day After Tomorrow.
Study co-author Richard Alley of Pennsylvania State University compared the threat of abrupt climate change effects to the random danger of drunk drivers.
"You can't see it coming, so you can't prepare for it. The faster it is, the less you see it coming, the more it costs," Alley said.
"If you see the drunk driver coming, you can get out of the way."
