Star Phoenix Base

By David L. Brown

We have written much here about the possibility of the global climate reaching tipping points, the result of feedback effects that might culminate in sudden and dramatic changes in temperature, weather patterns, rainfall, and other factors. Many climate experts have been warning that such events are not only possible, but likely. The idea was presented (albeit in an exaggerated and unlikely way) in the stupid movie “The Day After Tomorrow,” in which a reversal of the Atlantic thermohaline conveyor was supposed to put the eastern U.S. into an instant deep freeze.

Well, now there is evidence that extreme climate change can take place suddenly and irreversibly, perhaps in a single year. The evidence comes from new ice cores being studied from the Greenland Ice Sheet, where year-by-year snowfall layers provide a picture of the past. The story is reported on the Scientific American web site here. Here is the lede from the story:

Roughly 14,700 years ago the weather patterns that bring snow to Greenland shifted from one year to the next—a pattern of abrupt change that was repeated 12,900 years ago and 11,700 years ago when the earth’s climate became the one enjoyed today—according to records preserved in an ice core taken from the northern island. These speedy changes—transitions from warming to cooling and back again—in the absence of changes in greenhouse gas could presage abrupt, catastrophic climate change in our future.

According to the article, the abrupt changes were caused by shifts in air circulation, “and these changes took place from one year to the next more or less,” says glaciologist Sune Olander Rasmussen of the Centre for Ice and Climate at the University of Copenhagen, one of the researchers.

This is ominous news for it indicates the possibility of a catastrophic climate event that could take place with little or no warning, and leaving no time for human civilization to adapt. Unfortunately, even the most sophisticated climate models cannot predict such events; they defy definition because they represent sharp breaks with former trends.

Here is another passage from the Scientific American article, offering more evidence that the Greenland Ice Sheet may be far less stable than has been thought:

Greenland can change quickly, even living up to its name, according to another paper in this week’s Science. Sediment cores from the ocean show that forests of spruce and even fern grew on Greenland just 125,000 years ago. That means Greenland’s ice sheet—potentially responsible for as much as 75 feet (23 meters) of sea-level rise if it all melts—has grown and shrunk far more frequently than previously known.

NASA climate expert James Hansen has recently renewed warnings of possible tipping points in an article published in the 2008-9 State of the Wild, an annual publication of the Wildlife Conservation Society. The article is titled “Tipping Point, Perspective of a Climatologist.” Here is a key quote from Hansen’s article:

Our home planet is dangerously near a tipping point at which human-made greenhouse gases reach a level where major climate changes can proceed mostly under their own momentum. Warming will shift climatic zones by intensifying the hydrologic cycle, affecting freshwater availability and human health. We will see repeated coastal tragedies associated with storms and continuously rising sea levels. The implications are profound, and the only resolution is for humans to move to a fundamentally different energy pathway within a decade. Otherwise, it will be too late for one-third of the world’s animal and plant species and millions of the most vulnerable members of our own species.

Umm, ominous words indeed. And the latest report from the Greenland ice cores supports Hansen’s thesis that sudden tipping points are possible. As we have documented here, the melting of the Arctic sea ice is progressing with ever increasing speed. Only about three years ago scientists believed it would be 100 years before the last of the polar ice would be gone. Within a year they dropped their prediction to 30 years, and now some believe it could happen by 2015. Last summer saw the ice melting like a popsicle in July. The melting is likely to accelerate even faster, as demonstrated in this chart from NASA that illustrates what is happening in the Far North:

The diagram indicates the age of the ice, as observed between 1985-2000 and as of February this year at right. Note the widespread amount of “new,” one year old ice that was present in February, and how much of the older ice has disappeared. Obviously, new ice is far more susceptible to melting in the Summer heat, so one might conclude that the red areas will become open water this Summer. Other data I recently saw indicated that the thickness of the Arctic sea ice has declined precipitously, and it is becoming more and more obvious that the Arctic Ocean will be essentially ice free in the fairly near future. Snow and ice reflects solar heat back into space, but open water absorbs and stores the heat. The long Arctic summers with 24 hour sunlight will allow the ocean waters to soak up vast amounts of solar radiation, growing warmer and warmer like a saucepan on slow simmer.

As Hansen warns, that is exactly the kind of powerful feedback effect that can cause tipping points to be reached, and something like that could cause drastic changes in the world’s climate, perhaps not quite as sudden or dramatic as the unlikely events portrayed in the stupid movie “The Day After Tomorrow,” but serious enough to threaten the very continuation of civilization.

Meanwhile climate change deniers continue to be convinced that there is no such thing as global warming, or if there is that it will be a good thing because they won’t have to shovel snow from their driveway. Consider that the climate change observed in the Greenland ice cores amounted to as much as 20 degrees F. of warming, all in the space of only about one year. Now something like that would be real cause for concern, and it could happen almost any time, on a planet near you.