The Current Wisdom is a monthly series in which Senior Fellow Patrick J. Michaels reviews interesting items on global warming in the scientific literature that may not have received the media attention that they deserved, or have been misinterpreted in the popular press.
The Current Wisdom only comments on science appearing in the refereed, peer-reviewed literature, or that has been peer-screened prior to presentation at a scientific congress.
This year's installment of the United Nations' annual climate summit (technically known as the 16th meeting of the Conference of the Parties to the Framework Convention on Climate Change) has come and gone in Cancun. Nothing substantial came of it policy-wise; just the usual attempts by the developing world to shake down our already shaky economy in the name of climate change. News-wise probably the biggest story was that during the conference, Cancun broke an all time daily low temperature record. Last year's confab in Copenhagen was pelted by snowstorms and subsumed in miserable cold. President Obama attended, failed to forge any meaningful agreement, and fled back to beat a rare Washington blizzard. He lost.
But surely as every holiday season now includes one of these enormous jamborees, dire climate stories appeared daily. Polar bear cubs are endangered! Glaciers are melting!!
Or so beat the largely overhyped drums, based upon this or that press release from Greenpeace or the World Wildlife Fund.
And, of course, no one bothered to mention a blockbuster paper appearing in Nature the day before the end of the Cancun confab, which reassures us that Greenland's ice cap and glaciers are a lot more stable than alarmists would have us believe. That would include Al Gore, fond of his lurid maps showing the melting all of Greenland's ice submerging Florida.
Ain't gonna happen.
The disaster scenario goes like this: Summer temperatures in Greenland are warming, leading to increased melting and the formation of ephemeral lakes on the ice surface. This water eventually finds a crevasse and then a way down thousands of feet to the bottom of a glacier, where it lubricates the underlying surface, accelerating the seaward march of the ice. Increase the temperature even more and massive amounts deposit into the ocean by the year 2100, catastrophically raising sea levels.
According to Christian Schoof of the University of British Columbia (UBC), "The conventional view has been that meltwater permeates the ice from the surface and pools under the base of the ice sheet... .This water then serves as a lubricant between the glacier and the earth underneath it... ."
And, according to Schoof, that's just not the way things work. A UBC press release about his Nature article noted that he found that "a steady meltwater supply from gradual warming may in fact slow down the glacier flow, while sudden water input could cause glaciers to speed up and spread."
Indeed, Schoof finds that sudden water inputs, such as would occur with heavy rain, are responsible for glacial accelerations, but these last only one or a few days.
The bottom line? A warming climate has very little to do with accelerating ice flow, but weather events do.
How important is this? According to University of Leeds Professor Andrew Shepherd, who studies glaciers via satellite, "This study provides an elegant solution to one of the two key ice sheet instability problems" noted by the United Nations in their last (2007) climate compendium. "It turns out that, contrary to popular belief, Greenland ice sheet flow might not be accelerated by increased melting after all," he added.
I'm not so sure that those who hold the "popular belief" can explain why Greenland's ice didn't melt away thousands of years ago. For millennia, after the end of the last ice age (approximately 11,000 years ago) strong evidence indicates that the Eurasian arctic averaged nearly 13°F warmer in July than it is now.
That's because there are trees buried and preserved in the acidic Siberian tundra, and they can be carbon dated. Where there is no forest today — because it's too cold in summer — there were trees, all the way to the Arctic Ocean and even on some of the remote Arctic islands that are bare today. And, back then, thanks to the remnants of continental ice, the Arctic Ocean was smaller and the North American and Eurasian landmasses extended further north.
That work was by Glen MacDonald, from UCLA's Geography Department. In his landmark 2000 paper in Quaternary Research, he noted that the only way that the Arctic could become so warm is for there to be a massive incursion of warm water from the Atlantic Ocean. The only "gate" through which that can flow is the Greenland Strait, between Greenland and Scandinavia.
So, Greenland had to have been warmer for several millennia, too.
Now let's do a little math to see if the "popular belief" about Greenland ever had any basis in reality.
In 2009 University of Copenhagen's B. M. Vinther and 13 coauthors published the definitive history of Greenland climate back to the ice age, studying ice cores taken over the entire landmass. An exceedingly conservative interpretation of their results is that Greenland was 1.5°C (2.7°F) warmer for the period from 5,000-9000 years ago, which is also the warm period in Eurasia that MacDonald detected. The integrated warming is given by multiplying the time (4,000 years) by the warming (1.5°), and works out (in Celsius) to 6,000 "degree-years."
Now let's assume that our dreaded emissions of carbon dioxide spike the temperature there some 4°C. Since we cannot burn fossil fuel forever, let's put this in over 200 years. That's a pretty liberal estimate given that the temperature there still hasn't exceeded values seen before in the 20th century. Anyway, we get 800 (4 x 200) degree-years.
If the ice didn't come tumbling off Greenland after 6,000 degree-years, how is it going to do so after only 800? The integrated warming of Greenland in the post-ice-age warming (referred to as the "climatic optimum" in textbooks published prior to global warming hysteria) is over seven times what humans can accomplish in 200 years. Why do we even worry about this?
So we can all sleep a bit better. Florida will survive. And, we can also rest assured that the UN will continue its outrageous holiday parties, accomplishing nothing, but living large. Next year's is in Durban, South Africa, yet another remote warm spot hours of Jet-A away.
MacDonald, G. M., et al., 2000. Holocene treeline history and climatic change across Northern Eurasia. Quaternary Research 53, 302-311.
Schoof, C., 2010. Ice-sheet acceleration driven by melt supply variability. Nature 468, 803-805.
Vinther, B.M., et al., 2009. Holocene thinning of the Greenland ice sheet. Nature 461, 385-388.