Even "moderate additional" greenhouse emissions are likely to push Earth past "critical tipping points" with "dangerous consequences for the planet," according to research conducted by NASA and the Columbia University Earth Institute.
With just 10 more years of "business as usual" emissions from the burning of coal, oil and gas, says the NASA/Columbia paper, "it becomes impractical" to avoid "disastrous effects."
The study appears in the journal Atmospheric Chemistry and Physics. Its lead author is James Hansen, director of NASA's Goddard Institute for Space Studies in New York.
The forecast effects include "increasingly rapid sea-level rise, increased frequency of droughts and floods, and increased stress on wildlife and plants due to rapidly shifting climate zones," according to the NASA announcement.
By heralding the new research paper, NASA is endorsing science that places considerably more urgency on the need to reduce emissions to avoid "disastrous effects" of global warming than was evident in the recent reports from the world's scientists coordinated by the Intergovernmental Panel on Climate Change.
The new NASA release emphasizes the danger of "strong amplifying feedbacks" pushing Earth past "dangerous tipping points."
Scientists have been warning for several years that such tipping points are the greatest threat from manmade global warming — and what makes it potentially catastrophic for civilization.
As the tipping points pass, "there is an acceleration, potentially uncontrollable, of emissions of vast natural stores of greenhouse gas," according to Hansen, who reviewed the study for ABC News today.
Hansen explains that dangerous feedback loops are being tracked in various regions of the planet.
Many studies have reported feedback loops already observed in thawing tundra, seabeds and drying forests.
Hansen also points out that dark — and therefore heat-absorbing — forests are now expanding toward the Arctic, replacing lighter-colored areas such as tundra and snow cover.
The NASA research also reasserts the importance of the disappearing Arctic sea ice and snow, whose reflectivity has helped cool the planet by bouncing warm sunlight straight back into space.
The disappearance of that bright sea ice and snow is uncovering more and more dark water and bare ground — creating another dangerous feedback loop.
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 circle.
The recent IPCC summaries entertained "scenarios" of CO2 concentrations in the atmosphere ranging from 450 parts per million (ppm) up through 550 ppm and 650 ppm.
This new research says "C02 exceeding 450 ppm is almost surely dangerous."
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.