A new study warns that global climate change, often seen as a gradual process that stretches over thousands of years, can and has occurred abruptly and unexpectedly. The study finds that human impact on the environment could trigger sudden events like floods and droughts with devastating consequences.

The National Research Council, a group that advises the U.S. Congress on science and technology, asked a panel of scientists to take a closer look at the possibility of abrupt changes in climate. "What we do know is that we are going to be surprised. Big changes are likely somewhere out there. And, they are going to be hard to predict," says Richard Alley of Pennsylvania State University, chairman of the panel that wrote the report. He says the climate record, as documented in ice cores, tree rings and lake and ocean sediment, is punctuated with episodes of change as rapid as 10 degrees Celsius over just a few years.

"Some of these very big changes that happened during the cooling into the last ice age and the warming out of the last ice age seemed to have been linked to changes in the way the ocean circulates as well as the way in which the atmosphere works," he says.

Throughout history societies have adapted to these changes by moving indoors, irrigating crops and migrating away from inhospitable regions. But Richard Alley warns these adaptations are likely to be more difficult now because of human impact on the environment.

He says by cutting down trees, diverting rivers, building dams and emitting greenhouse gases into the atmosphere, humans have become an instrument of climate change. "It isn't that humans are worse than nature in some way. It is just that we are pushing the system. We are pushing on the switch. And, by causing climate change we make an abrupt one more likely."
Q:"And, what would be the most immediate dangers of abrupt climate change?"
"In terms of looking for danger, it is probably what happens to people in ecosystems. We live with a lot of different climates. But, we have built for the conditions we have. We have the right number of heaters and air conditioners, wells, dams and so on. And if you have any sort of climate change, it will require us to adapt to that change. If something happens, we will have costs. If those costs come slowly they are easy to deal with. If they come fast they are hard to deal with. And so the real issues become how do we as humans and how do natural ecosystems deal with an abrupt change? Certainly in the past, nature had abrupt climate changes before we were causing them, and so ecosystems have certainly dealt with them. But they haven't dealt with them when there are interstate highways and cornfields in the way. And, so if you have an abrupt climate change and the plants living where you are really should now be living 1,000 miles to the north, can they get there when there is an interstate highway and a cornfield in the way?"

The report says abrupt change could cause droughts and floods that could affect agriculture, water supply and bio-diversity around the planet. Richard Alley says the possibility of abrupt change is not a cause for panic, but rather a warning for policy makers to consider ways to reduce the impact of climate change. "Let's look for the key places where an abrupt climate change might happen. Let's get good observing systems so we can see one coming. Let's try to understand them better so we can understand how long they can be, how big they can be, how destructive they can be, and then let's look for ways that we can bend natural and human systems rather than breaking them."

The National Research Council report discusses what it calls "no-regrets strategies" that could be put in to help mitigate change. These could include measures to reduce emissions to slow global warming, to improve climate forecasting, to slow the loss of bio-diversity, and to improve land and air quality.