New Ice Age Predicted — But Averted by Global Warming?
by Mason Inman, National Geographic News, November 12, 2008 [here]
Deep ice sheets would cover much of the Northern Hemisphere thousands of years from now—if it weren’t for us pesky humans, a new study says.
Emissions of greenhouse gases—such as the carbon dioxide, or CO2, that comes from power plants and cars—are heating the atmosphere to such an extent that the next ice age, predicted to be the deepest in millions of years, may be postponed indefinitely (quick guide to the greenhouse effect).
“Climate skeptics could look at this and say, CO2 is good for us,” said study leader Thomas Crowley of the University of Edinburgh in Scotland.
But the idea that global warming may be staving off an ice age is “not cause for relaxing, because we’re actually moving into a highly unusual climate state,” Crowley added.
In about 10,000 to 100,000 years, the study suggests, Antarctic-like “permanent” ice sheets would shroud much of Canada, Europe, and Asia.
“I think the present [carbon dioxide] levels are probably sufficient to prevent that from ever happening,” said Crowley, whose study will appear tomorrow in the journal Nature.
Permanent Ice Sheets?
For the past three million years, Earth’s climate has wobbled through dozens of ice ages, with thick ice sheets growing from the poles and then shrinking back again.
These ice ages used to last roughly 41,000 years. But in the past half a million years, these big freezes each stretched to about a hundred thousand years long.
Meanwhile, the temperature swings during and between these ice ages became more extreme, soaring to new highs and lows.
These extreme climate swings don’t appear to be easing anytime soon, according to evidence recorded in Earth’s rocks, Crowley said. “The latest two glaciations were two of the biggest we’ve seen.”
The increasing variability is a sign that Earth’s climate will soon move into a new state, according to a computer model used by Crowley and a colleague, William Hyde of the University of Toronto in Canada. They had previously used the model to simulate past ice ages. [more]
by YPmule
I’ve been doing a lot of reading on post Ice vegetation and warming trends. Every time it gets warmer human population increases (due to ability to grow more food in more places.)
Where we live, winters have been milder than in the memories of the old timers. From listening to them, I’m glad we don’t get 4-6 feet of snow and minus 20F temps!
YP — I have a data set of snowpack (snow-water equivalent measurements) for Idaho that goes back to 1918. While there have been heavy years and light years, the average has not changed in any direction in all that time. I will have to dig those records out and post them.
by YPmule
Thanks Mike - I’m sure that folks tend to remember the hard winters over mild ones. Of the last 10 winters here - no two have been alike, so I am starting to think that there is no such thing as an “average winter”!
YP — you are absolutely correct that there is no such thing as an average winter. Averages are mathematical constructs, not real phenomena.
What I meant to say is that there has been no statistical trend since 1918 towards heavier or lighter snowpack. The trend line is flat. It doesn’t go up and it doesn’t go down. I will post the graph soon.
Like a passing comet this article skirts close to the truth but doesn’t quite hit it.
The 41,000 and 100,000 year Ice Age return periods conform exactly to Milankovitch cycles, eccentricities in the Earth’s orbit [here]. The series of Ice Ages began when Antarctica tectonically drifted over the South Pole and broke free of South America some 2.5 million years ago. Taking all that into account means that CO2 is very unlikely to avert the next, inexorable, coming Ice Age. We can hope, however.
Also, the study apparently fails to mention that anthropogenic fire has been going on world-wide since the Holocene began. Man has been injecting CO2 into the atmosphere for 10,000 years (and up to 40,000 years in some places), quite possibly in greater quantities than today. But it may be that the Holocene is hanging on a little longer than the Eemian, the previous interglacial that petered out as the Earth slid into the Wisconsin glaciation some 100,000 years ago. So maybe there IS some effect from anthropogenic carbon dioxide.
Many people have no problem with continental ice sheets grinding Chicago, Montreal, NYC etc. into glacial dust. But there are other side-effects that might be less satisfying. In any case, it will be awhile before the next Ice Age hits. In the meantime,
Warmer is Better. Fight the Ice.