PDA

View Full Version : Global warming divert ice age?


Potemkin
12-18-2008, 09:13 PM
http://www.sciencedaily.com/releases/2008/12/081217190433.htm

Did Early Global Warming Divert A New Glacial Age?
enlarge

Glacier and mountain peaks in East Greenland. Using three different climate models and removing the amount of greenhouse gases humans have injected into the atmosphere during the past 5,000 to 8,000 years, scientists observed more permanent snow and ice cover in regions of Canada, Siberia, Greenland and the Rocky Mountains, all known to be seed regions for glaciers from previous ice ages. (Credit: iStockphoto/Rob Broek)

ScienceDaily (Dec. 18, 2008) — The common wisdom is that the invention of the steam engine and the advent of the coal-fueled industrial age marked the beginning of human influence on global climate.

But gathering physical evidence, backed by powerful simulations on the world's most advanced computer climate models, is reshaping that view and lending strong support to the radical idea that human-induced climate change began not 200 years ago, but thousands of years ago with the onset of large-scale agriculture in Asia and extensive deforestation in Europe.

What's more, according to the same computer simulations, the cumulative effect of thousands of years of human influence on climate is preventing the world from entering a new glacial age, altering a clockwork rhythm of periodic cooling of the planet that extends back more than a million years.

"This challenges the paradigm that things began changing with the Industrial Revolution," says Stephen Vavrus, a climatologist at the University of Wisconsin-Madison's Center for Climatic Research and the Nelson Institute for Environmental Studies. "If you think about even a small rate of increase over a long period of time, it becomes important."

Addressing scientists on Dec 17 at a meeting of the American Geophysical Union, Vavrus and colleagues John Kutzbach and Gwenaëlle Philippon provided detailed evidence in support of a controversial idea first put forward by climatologist William F. Ruddiman of the University of Virginia. That idea, debated for the past several years by climate scientists, holds that the introduction of large-scale rice agriculture in Asia, coupled with extensive deforestation in Europe began to alter world climate by pumping significant amounts of greenhouse gases — methane from terraced rice paddies and carbon dioxide from burning forests — into the atmosphere. In turn, a warmer atmosphere heated the oceans making them much less efficient storehouses of carbon dioxide and reinforcing global warming.

That one-two punch, say Kutzbach and Vavrus, was enough to set human-induced climate change in motion.

"No one disputes the large rate of increase in greenhouse gases with the Industrial Revolution," Kutzbach notes. "The large-scale burning of coal for industry has swamped everything else" in the record.

But looking farther back in time, using climatic archives such as 850,000-year-old ice core records from Antarctica, scientists are teasing out evidence of past greenhouse gases in the form of fossil air trapped in the ice. That ancient air, say Vavrus and Kutzbach, contains the unmistakable signature of increased levels of atmospheric methane and carbon dioxide beginning thousands of years before the industrial age.

"Between 5,000 and 8,000 years ago, both methane and carbon dioxide started an upward trend, unlike during previous interglacial periods," explains Kutzbach. Indeed, Ruddiman has shown that during the latter stages of six previous interglacials, greenhouse gases trended downward, not upward. Thus, the accumulation of greenhouse gases over the past few thousands of years, the Wisconsin-Virginia team argue, is very likely forestalling the onset of a new glacial cycle, such as have occurred at regular 100,000-year intervals during the last million years. Each glacial period has been paced by regular and predictable changes in the orbit of the Earth known as Milankovitch cycles, a mechanism thought to kick start glacial cycles.

"We're at a very favorable state right now for increased glaciation," says Kutzbach. "Nature is favoring it at this time in orbital cycles, and if humans weren't in the picture it would probably be happening today."

Importantly, the new research underscores the key role of greenhouse gases in influencing Earth's climate. Whereas decreasing greenhouse gases in the past helped initiate glaciations, the early agricultural and recent industrial increases in greenhouse gases may be forestalling them, say Kutzbach and Vavrus.

Using three different climate models and removing the amount of greenhouse gases humans have injected into the atmosphere during the past 5,000 to 8,000 years, Vavrus and Kutzbach observed more permanent snow and ice cover in regions of Canada, Siberia, Greenland and the Rocky Mountains, all known to be seed regions for glaciers from previous ice ages. Vavrus notes: "With every feedback we've included, it seems to support the hypothesis (of a forestalled ice age) even more. We keep getting the same answer."

Fiddlerdave
12-19-2008, 03:01 PM
This work is further confirmation of the effect of human-produced CO2 on Global Warming.

The idea that human effect on increasing CO2 has possibly prevented an cold period or ice age has been around for a while, and it is interesting to see some more scientific basis for it. But note simple agricultural work was enough, the Industrial Revolution is, as the authors note ""The large-scale burning of coal for industry has swamped everything else" in the record".

Turning up the heat a little was quite possibly a Good Thing. Unfortunately, since we started burning coal and oil in huge quantities we keep turning the burner up higher and higher every year, many times the small initial amount that was enough to stop an Ice Age. What effect will many, many times that early small CO2 increase produce?

It is a fact there can be too much of a Good Thing.

Fattail
12-23-2008, 10:57 AM
7 billion people on the planet need long growing seasons. We saw what prices did last winter in wheat and rice when regional stocks got to low. The hoarding began at $9.00 for wheat and about $15.00 for rice. The rioting last year in Egypt and some of the other third world importers was caused by price. What will they do when they are hungry? More importantly what will their gov't do to qwell the masses? False flag operations against their neighbor with food reserves?

The social costs of a global warming are miniscule compared to those of a cooling period such as the mini ice age prior to 1850, or new global ice age, which we are due.

hillsidedigger
12-23-2008, 11:06 AM
7 billion people on the planet need long growing seasons. We saw what prices did last winter in wheat and rice when regional stocks got to low. The hoarding began at $9.00 for wheat and about $15.00 for rice. The rioting last year in Egypt and some of the other third world importers was caused by price. What will they do when they are hungry? More importantly what will their gov't do to qwell the masses? False flag operations against their neighbor with food reserves?

The social costs of a global warming are miniscule compared to those of a cooling period such as the mini ice age prior to 1850, or new global ice age, which we are due.

7 billion people on this planet cannot last but a short time before largescale regional die-offs commence irregardless of what happens with the climate.

Any disruption of agriculture by a changing climate would be for the worse. Longer growing seasons would mean farmers would need to revise their time-tested procedures and crops plus likely would be mean more drought and pestilence.