Hansen's concern is predicated on the concept of a "
In the University of Iowa speech, Hansen recounted how NASA Administrator Sean O'Keefe told him in a 2003 meeting that he shouldn't talk "about dangerous anthropogenic interference" -- humans' influence on the atmosphere -- "because we do not know enough or have enough evidence for what would constitute dangerous anthropogenic interference."
But Hansen said that scientists know enough to conclude we have reached this danger point and that their efforts to get the word out are being blocked by the administration. "In my more than three decades in government, I have never seen anything approaching the degree to which information flow from scientists to the public has been screened and controlled as it has now," Hansen said. He added that although the administration wants to wait 10 years to evaluate climate change, "delay of another decade, I argue, is a colossal risk."
As the tipping points pass, "there is an acceleration, potentially uncontrollable, of emissions of vast natural stores of greenhouse gas," according to Hansen.....
The disappearance of that bright sea ice and snow is uncovering more and more dark water and bare ground — creating another dangerous feedback loop.
Given this scenario, some economic advisors are suggesting that the best course of action may be adaptation rather than prevention. Hansen disagrees.
These feedbacks all produce more heat, thus all reinforcing each other, leading to evermore thawing — and thus releases of natural greenhouse gases (including CO2 and methane) in a viciously accelerating circlering more and more dark water and bare ground — creating another dangerous feedback loop.
According to the Intergovernmental Panel on Climate Change, scenarios modeled by scientists predict CO2 emissions rise to anywhere from a low of 450 ppm (parts per million) to as high as 650 ppm.
But not to worry - after
Hansen told ABC News today he believes the upper limit for avoiding dangerous climate change "could well be much lower" than 450 ppm.
In the NASA announcement, Hansen said, "'business as usual' emissions would be a guarantee of global and regional disaster."
Earth's CO2 concentration is currently 383 ppm, up from 280 ppm at the start of the industrial age.
Studies released earlier this month report human-made emissions now spiraling upward at an accelerating rate much faster than scientists expected only a few years ago.