Giant Glacier Breaks on Anniversary of Global Warming

On Thursday, scientists discovered that a huge mass of ice four times the size of Manhattan had broken free of Petermann glacier in northwestern Greenland. The "ice island" was the largest calving event on the glacier since 1962, and researchers estimated Petermann lost nearly a quarter of its floating ice tongue in one go.

Any individual calving event, like a bad storm, wildfire, or flood, is not necessarily a symptom of global warming. But large bergs also crumbled off Petermann in in 2001 and 2008, and Jason Box of Ohio State University has been studying the glacier -- and expecting this breakup event -- for some time. He said the glacier's behavior in recent years is "all part of a climate warming pattern."

As it turns out, the new ice island was born just in time for the 35th anniversary of the scientific paper that coined the term "global warming." On August 8,1975, the journal Science published the article entitled "Are We on the Brink of a Pronounced Global Warming?" by Wallace Smith Broecker of Columbia University.

Concerns about man-made global warming had been uttered before, from the halls of Congress to educational science videos, but Broecker's work laid out the issue in stark terms and it came with a prediction for the future. Here is his remarkably simple, elegant abstract:

If man-made dust is unimportant as a major cause of climatic change, then a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide. By analogy with similar events in the past, the natural climatic cooling which, since 1940, has more than compensated for the carbon dioxide effect, will soon bottom out. Once this happens, the exponential rise in the atmospheric carbon dioxide content will tend to become a significant factor and by early in the next century will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years.

The first caveat about man-made dust is still something climate scientists debate. Its ability to block sunlight dampens the effects of greenhouse gases somewhat, but CO2 swamps this effect, and the temperature records are fairly undeniable (see below).

Though Broecker eschews much of the media attention that comes with being heralded as one of the "fathers of global warming," his contribution is hard to overstate. In a stroke he offered a glimpse of what climate science was (and is, now more than ever) capable of: not only understanding past changes in the Earth system, but predicting how that system will behave in the future.

Broecker's predictions proved to be pretty accurate. A figure from his paper suggests that global temperature anomalies might be about 0.8 degrees Celsius (1.4 degrees Fahrenheit) by 2010:

By comparison, the latest data from NASA's Goddard Institute of Space Studies shows that temperatures have climbed about 0.6 C since the 1940s and 0.8 C since the 1880s (the zero in the figure below is a measure of average monthly temperature from 1951-1980. Explanation here.):

At the time, the science of climate prediction was far less refined than it is today. And yet for the most part, Broecker got it right:

The major point of the argument is that over the past 30 years the warming trend due to CO2 has been more than countered by a natural cooling. This compensation cannot long continue both because of the rapid growth of the CO2 effect and because the natural cooling will almost certainly soon bottom out. We may be in for a climatic surprise. The onset of the era of CO2-induced warming may be much more dramatic than in the absence of natural climatic variations.

The agricultural consequences of this ensuing warming are not obvious (neither are the implications to global sea level). A knowledge of the mean global temperature tells us little about the rainfall patterns in the chief grain-producing regions. There is little doubt, however, that this gradual warming will lead to changes in the pattern of global precipitation. Our efforts to understand and eventually to predict these changes must be redoubled. (emphasis added)

It is perhaps fair that the businesses, governments, and people of the world did not instantly heed his warning. After all, it was just one single scientist writing one single article, right?

Thirty-five years later, Broecker's predictions have turned out more or less as he called them (and thousands of scientific papers now back up the trend he identified). The phrase "global warming" itself has become so politically charged that all the temperature records, tide gauges, and satellite photos of crumbling and melting Petermann glaciers in the world can't convince anyone who isn't already that climate change is proceeding in earnest, and that it must be urgently dealt with. Instead of "redoubled efforts," failed climate talks, legislation, and economic hand-wringing are the norm.

Broecker has moved on. He is researching ways that we can capture and store carbon dioxide from the atmosphere -- new ideas and technologies that will forestall catastrophic climate change and allow our civilization to continue to live and prosper on this planet.

Maybe it's time we finally took a page out of his book.

Images: Andreas Muenchow, University of Delaware
; Science; NASA