It also means that scientists and other experts are going to have to monitor measures other than just atmospheric concentration of greenhouse gases to catch catastrophic climate change developing. "It is essential that we designate the harbingers of abrupt and significant changes or, perhaps more importantly, the triggers and thresholds that could commit the planet to these changes well before their tell-tale signs appear," says economist and IPCC author Gary Yohe of Wesleyan University in Middletown, Conn. "We cannot accept the adaptive design completely without having confidence in our abilities to determine exactly what to monitor."
The IPCC has taken a crack at that, identifying 26 "key vulnerabilities" in its most recent assessment, ranging from declines in agricultural productivity to the melting of ice sheets and polar ice cover as well as determining how to judge if they are spiraling out of control. Disappearing Arctic ice is already helping to amplify global warming beyond what the IPCC had predicted in the past. "We already know about as much as we are going to about climate system's response to greenhouse gases," Roe says. "We already have the basis for making the decisions we need to make."