Predicting how bad climate change will be maybe impossible

A new scientific paper is making the news; says it's real hard to predict what will happen with climate change, as lack much necessary info. To idiots (eg see below) seems this means that can't predict anything about it; but that's not what the scientists say - instead, warming will happen, but it's possible there could be significantly worse things to come than various scenarios suggest, and we need flexible responses. From Scientific American site:

... neither this international team of experts nor any other can say with any certainty just how bad global warming may get. There is a simple explanation for this, says atmospheric physicist Gerard Roe of the University of Washington (U.W.) in Seattle: Earth's climate is extremely sensitive. In other words, small changes in various physical processes that control climate lead to big results. "If nothing else changed by [warming], a doubling of carbon dioxide would ultimately lead to a temperature change of about 1.2 [degrees] C," [(2.1 degrees F)] Roe says. "In fact, because of internal processes within the climate system, such as changing snow cover, clouds and water vapor in the atmosphere, our best estimate is that the actual warming would be two to four times larger than that."

Some of these feedback processes are poorly understood—like how climate change affects clouds—and many are difficult to model, therefore the climate's propensity to amplify any small change makes predicting how much and how fast the climate will change inherently difficult. "Uncertainty and sensitivity are inextricably linked," Roe says.

"Some warming is a virtual certainty, but the amount of that warming is much less certain." Roe and his U.W. co-author, atmospheric physicist Marcia Baker, argue in Science that, because of this inherent climate effect, certainty is a near impossibility, no matter what kind of improvements are made in understanding physical processes or the timescale of observations. "Once the world has warmed 4 degrees C [(7.2 degrees F)] conditions will be so different from anything we can observe today (and still more different from the last ice age) that it is inherently hard to say when the warming will stop," physicists Myles Allen and David Frame of the University of Oxford wrote in an editorial accompanying the article. ...

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."

Climate"> Change's Uncertainty Principle Scientists say they can never be sure exactly how extreme global warming might become, but that's no excuse for delaying action I've seen a rabid rightie blog post suggesting this means all climate change science is bogus (but not this paper!). Commented to the author:

Suppose some pinko-liberal or even commie country were to go to war with the US of A - exactly how many people would die? Or even if some terrorists let off a few dirty bombs in some US cities, how many would die now and in future, inc from side effects? You can't predict for sure? Then - according to your absurd piece on American Idiot (Thinker? - hahahaha, gimme a break) these are not real threats, and we shouldn't do anything to prevent them happening.
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