Study of Greenland Ice Finds Rapid Change in Past Climate

[there buster]

Study of Greenland Ice Finds Rapid Change in Past Climate

By WALTER SULLIVAN

Published: July 15, 1993

To the astonishment of climate specialists, an analysis of ice extracted from the full depth of the Greenland ice sheet has shown that except for the 8,000 to 10,000 years since the last glacial epoch, the climate over the past 250,000 years has changed frequently and abruptly.

The findings suggest that the period of stable climate in which human civilization has flourished might be unusual, and that the current climate may get either warmer or colder much more quickly than had been believed -- in spans of decades or even less.

The data are likely to bolster concern that future changes in climate might not be spread over many centuries, allowing farmers to adjust to altered growing conditions and coastal cities to deal with rising sea levels, for example.

Scientists have speculated for years about the effects of climate warming. Even a rise of a few feet in sea level would flood many food-producing regions and populous areas.

Commenting on the new research, Dr. Andrew J. Weaver of the University of Victoria in British Columbia said that if the climate became colder Europe would be covered with snow much longer. As glaciers advanced, he said, they would reflect more of the Sun's energy back into space, chilling the climate even more. Warmer and Colder Periods

The scientists said their data showed that significantly warmer periods and significantly colder periods had occurred during the last interval between glacial epochs, about 115,000 to 135,000 years ago. They said they could not tell whether that meant similar changes were in store. Their findings were reported today in two papers in the journal Nature.

Previous studies had shown that there were abrupt changes in climate during glacial epochs, but the new results show that the same was true in the periods when glaciers had retreated. In one "catastrophic event" during the last interglacial period, the average temperature plunged 25 degrees Fahrenheit to ice-age levels for about 70 years, the scientists reported.

The authors said they did not have an explanation for the rapid shifts. They also said it was a mystery why the climate of the last 8,000 to 10,000 years had been "strangely stable."

In a commentary in the journal, Dr. J. W. C. White of the Institute of Arctic and Alpine Research of the University of Colorado said it was "difficult to express the importance" of the reports on the ice findings. Need for 'Global Cooperation'

"Adaptation -- the peaceful shifting of food-growing areas, coastal populations and so on -- seemed possible, if difficult, when abrupt change meant a few degrees in a century," he wrote. "It now seems a much more formidable task, requiring global cooperation with swift recognition and response."

The new studies found that the average global temperature can change as much as 18 degrees Fahrenheit in a couple of decades during interglacial periods, Dr. White said. The current average global temperature is 59 degrees Fahrenheit.

The Greenland studies are based on ice samples extracted by a consortium of scientists from eight European nations. They reached a depth of 9,938 feet, using a drill mounted on the crest of the Greenland ice cap, 10,624 feet above sea level. Silt in the lower 20 feet of ice indicated that bedrock was near.

The scientists meticulously examined various properties of the ice layers laid down each year by snowfall. The record of past climate was inferred from the analysis of oxygen in each layer of ice. The amount of a lighter form of oxygen relative to a heavier form is assumed to indicate the climate temperature when the snow fell.

The time scale for the last 14,500 years came from counting annual layers. Beyond that, age estimates were based on assumed accumulation rates.

In a separate project, scientists from more than 20 American universities and agencies have drilled at a site in Greenland 20 miles west of the Europeans. They have reached bottom, said Michael Morrison of the University of New Hampshire, associate director of the project.

They expect not only to confirm the European findings, but also to provide more detailed data on temperatures, atmospheric composition and ancient volcanic eruptions, particularly in the Northern Hemisphere.

The research on the last period between glaciers is considered important because it may provide hints about the effects of rising levels of atmospheric gases, like carbon dioxide, that have a warming effect similar to that caused by the glass in a greenhouse.

"As the last interglacial seems to have been slightly warmer than the present one," the new report said, "its unstable climate raises questions about the effects of future global warming." Hippos in the Thames

At one point between the last two glacial epochs, the climate melted enough polar ice to raise sea levels some 30 feet. As noted by a member of the drilling team, Dr. David A. Peel of the British Antarctic Survey, it was so warm in England that hippopotamuses wallowed in the Thames and lions roamed its banks.

One reason for special concern is the link between temperature and the atmospheric content of the so-called greenhouse gases. Early this year French researchers noted that microscopic air bubbles extracted from ancient ice in both Greenland and Antarctica have shown "a remarkable correlation" between a rise in atmospheric carbon dioxide and an increase in temperature.

Results from both the European and American ice cores, said a companion report in the current issue of Nature, "have revealed large, abrupt climate changes of at least regional extent during the late stages of the last glaciation." It said these suggest that "the climate in the North Atlantic region is apt to reorganize itself rapidly, perhaps even within a few decades."

The new findings show that such changes also occurred in the previous ice age and in the warm period in between. It had been assumed that climate during that interglacial period had been as stable as during the current post-glacial period.

Since the end of the last ice age, only moderate climate changes have occurred. These include the medieval warm period, when the Vikings settled Greenland, and the "Little Ice Age" from 1550 to 1850, when Pieter Bruegel, the 16th-century Flemish artist, painted scenes of ice skating.

The article was signed by eight scientists from the Niels Bohr Institute in Copenhagen, most of them co-authors of the primary report. They were led by Dr. Willi Dansgaard, a veteran of Greenland drilling. Other authors were from France, Iceland and the Lamont-Doherty Earth Observatory of Columbia University.

In his commentary, Dr. White wrote: "We humans have built a remarkable socioeconomic system during perhaps the only time when it could be built, when climate was sufficiently stable to allow us to develop the agricultural infrastructure required to maintain an advanced society. We don't know why we have been so blessed, but even without human intervention, the climate system is capable of stunning variability.

"If the Earth came with an operating manual, the chapter on climate might begin with a caveat that the system has been adjusted at the factory for optimum comfort, so don't touch the dials."

[Bravus]

But hang on - hasn't there only been a climate for 6000 years?

[there buster]

Facile, bur fallacious and evasive defense.

1) I have never made any claims about a 6000 year old Earth. To the contrary, I have stated the Bible is silent on the issue.

2) Those who promote the religion of global warming/global climate crisis do in fact share the assumptions of those cited in the article. But the global climate crisis gurus ignore the evidence contrary to their position, such as this study-- and many, many others-- provide.

3)As soon as the 'nuclear winter' nonsense was disproven, the global warming silliness began to be promoted. It has been going full voice for twenty years, and half of that time we've been cooling instead. The computer models on which the gloomy predictions are based don't even correctly predict what is happening now in different parts of the atmosphere. Sooner or later, it will be discredited totally, except among the true believers, who will still be waiting by abandoned global warming runways, waiting for the global warming cargo to be delivered.

[Bravus]

Or, you know, a brief joke in a situation where I know any more detailed response will simply be dismissed anyway and don't want to invest the time.

[Bravus]

Seriously then.

1. The reported findings are completely uncontroversial and unsurprising. Massive climate variation is a fact of life in Earth's history and this is well known. We live in a tiny island of stability in a sea of massive unpredictability, with a whole lot of relevant factors. This is well known science.

2. Nonetheless, human civilisation is based and premised on this island of stability, just a few thousands of years in extent. If there was a massive shift in climate, perhaps up to half the earth's population would die - and it might not be the half you'd guess. I personally think that is cause for concern to anyone but the most callous, and something we should do what we can to avert.

3. It's possible that there may be nothing we can do to avert it - it's true that all such prior rapid changes have happened without human intervention. In that case, we should stand ready to help those affected on a scale never seen before.

4. But as the final sentence in the initial article ichabod quoted said '...the system has been adjusted at the factory for optimum comfort, so don't touch the dials.' Like it or not, believe it or not, we're doing a massive uncontrolled experiment by doubling the concentration of the greenhouse gas carbon dioxide in the atmosphere.

To use the metaphor of a raft of stability in climate - one thing you *don't* do, if you're on a precarious raft in a freezing ocean (and assuming you're sane) is double the weight on one side of the raft as an experiment. The stability of climate is fragile, and we do know greenhouse gases are one important stabilising factor. Messing with them to an immense extent is not smart.

In short, the evidence that rapid climate change happens is hard for me to see in any way except as an urgent call for action on greenhouse gases, rather than support for doing nothing.

[Bravus]

In response to this claim, which is simply factually wrong on any data set:

Quote:

It has been going full voice for twenty years, and half of that time we've been cooling instead.

http://www.bravus.com/blog/?p=911

http://www.bravus.com/blog/?p=955

[Bravus]

http://www.ncar.ucar.edu/research/climate/now.php

[there buster]

http://www.nationalcenter.org/KyotoFactSheet.html

[Bravus]

http://www.ucar.edu/communications/newsreleases/2003/wigley2.html

(addresses just one of the distortions in the above 'Kyoto Fact Sheet': it is not true that satellite temperature data show cooling rather than warming. this has been known for years, but 'skeptics' keep on trotting it out anyway. of course, the 'fact sheet' itself is over 10 years old. science moves on)

[Bravus]

'course, that UCAR paper is 5 years old too. Will go looking for something newer.

[Bravus]

Here's an unbiased discussion from Nov 2007, which shows that there is some cooling in some layers of the atmosphere and warming in others, and discusses the effects of events like major volcanic eruptions: http://wattsupwiththat.wordpress.com/2007/11/26/the-scoop-on-satellite-temperature-data/

Some of the other stuff on that guy's site is worth a read too.