How it happened: The catastrophic flood that cooled the Earth

[ben_meyers]

I wonder what the humans were doing to cause this? Campfires maybe.

Discovery Channel did an excellent program on this event late last year.

Canadian geologists say they can shed light on how a vast lake, trapped under the ice sheet that once smothered much of North America, drained into the sea, an event that cooled Earth's climate for hundreds of years.
During the last ice age, the Laurentide Ice Sheet once covered most of Canada and parts of the northern United States with a frozen crust that in some places was three kilometres (two miles) thick.

As the temperature gradually rose some 10,000 years ago, the ice receded, gouging out the hollows that would be called the Great Lakes.

Beneath the ice's thinning surface, an extraordinary mass of water built up -- the glacial lake Agassiz-Ojibway, a body so vast that it covered parts of Manitoba, Saskatchewan, North Dakota, Ontario and Minnesota.

And then, around 8,200 years ago, Agassiz-Ojibway massively drained, sending a flow of water into the Hudson Strait and into the Labrador Sea that was 15 times greater than the present discharge of the Amazon River.

By some estimates, sea levels rose 14 metres (45 feet) as a result.

http://www.physorg.com/news123083709.html

[tabatha]

1. Where does that article talk about the influence of the

atmosphere on what happened?

Comparing apples with oranges with campfires.

[ben_meyers]

2. What caused the glacier to recede then?

That's the point. Glaciers recede and advance naturally, without human intervention.

edit to add:

During the last ice age, the Laurentide Ice Sheet once covered most of Canada and parts of the northern United States with a frozen crust that in some places was three kilometres (two miles) thick.

Where did that ice go? Why did it melt.

[OKIsItJustMe]

4. Yes, global warming and cooling happened long before we appeared on the scene

However, lightning can start forest fires, and did so long before we arrived on the scene. Does that mean that people can't start forest fires now?

[ben_meyers]

5. So you're are saying that a forest fire melted the

glaciers? That would be one explanation.

[NickB79]

6. Here that whistling sound?

That's the analogy that just flew right over your head :)

[ben_meyers]

8. No, I just didn't think I would have needed the sarcasm tag,

I was wrong.

[OKIsItJustMe]

9. No I was not suggesting that

You pointed out that glaciers advance and recede naturally, which is true. Your implication (correct me if I'm wrong here) was that the current period of melting is therefore not caused by us.

My point was that just because something can happen without our actions causing it (i.e. a forest fire starting or a glacier receding) does not mean that our actions cannot cause something to happen when it otherwise wouldn't have (i.e. we can start a forest fire or even kick off global warming.)


Looking at the natural cycle of ice ages, looking at "solar cycles" and "Milankovitch cycles," should we expect the currently observed (relatively rapid) global warming trend?

The answer (the vast majority of climatologists tell us) is "No."

[jpak]

13. Ever hear of Milankovitch Cycles???

Probably not

[Red Zelda]

10. Natural cycles occur

our fossil fuel burning is making it happen much, much faster.
Or maybe that fucker jesus is doing it! fucking sandal wearer!

[OKIsItJustMe]

3. They probably didn't do anything

It was probably "Milankovitch Cycles" which kicked off the warming that time.

[RC]

7. The weight of that glacier was so great it pushed down the earth crust.

That is why the Red River runs North. However the crust is slowly recovering and in about 10,000 years the Red River will stop flowing and Lake Agassiz will fill back up again, before finding an outlet southward.
I can hardly wait. I live at the bottom of a drain for three states. The water used to be 600 feet deep here

[kestrel91316]

11. A belated welcome to DU. You enjoy your little stay, now.

[ben_meyers]

12. Thank you again, for the 3rd time

I hope your shawl is still keeping you warm.

[jpak]

14. Try to debunk anthropogenic global warming all you want - you're still wrong...

Richard A. Kerr (2001) It's Official: Humans Are Behind Most of Global Warming
Science 2001. 291: 566 (commentary and summary of recent research)

J. E. Harries, H. E. Brindley, P. J. Sagoo, R. J. Bantges (2001). Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997. Nature 410: 355 - 357

T. P. Barnett, D. W. Pierce, R. Schnur (2001). Detection of Anthropogenic Climate Change in the World's Oceans. Science 292: 270-274.

S. Levitus, J. I. Antonov, J. Wang, T. L. Delworth, K. W. Dixon, and A. J. Broccoli (2001) Anthropogenic Warming of Earth's Climate System. Science 292: 267-270.

D. J. Karoly, K. Braganza, P. A. Stott, J. M. Arblaster, G. A. Meehl, A. J. Broccoli, and K. W. Dixon (2003) Detection of a Human Influence on North American Climate. Science. 302: 1200-1203

B. D. Santer, M. F. Wehner, T. M. L. Wigley, R. Sausen, G. A. Meehl, K. E. Taylor, C. Ammann, J. Arblaster, W. M. Washington, J. S. Boyle, and W. Brüggemann (2003) Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes. Science. 301: 479-483

P. A. Stott, D. A. Stone and M. R. Allen (2004) Human contribution to the European heatwave of 2003. Nature 432: 610-614

J. Hansen, L. Nazarenko, R. Ruedy, M Sato, J. Willis, A. Del Genio, D. Koch, A. Lacis, K. Lo, S. Menon, T. Novakov, J. Perlwitz, G. Russell, G. A. Schmidt N. Tausnev (2005) Earth's Energy Imbalance: Confirmation and Implications. Science. 308: 1431 – 1435

T. P. Barnett, D. W. Pierce, K. M. AchutaRao, P. J. Gleckler, B. D. Santer, J. M. Gregory, and W. M. Washington (2005) Penetration of Human-Induced Warming into the World's Oceans. Science. 309: 284-287

M. Lockwood and C. Frohlich (2007) Recent oppositely directed trends in solarclimate forcings and the global mean surface air temperature. Proc. R. Soc.doi:10.1098/rspa.2007.1880 Published online

oh yeah and this too...

[tinrobot]

15. Didn't cool enough to refreeze, though...

It was just a 200-400 year blip, then the planet started warming again.

[AlecBGreen]

16. you missed the operative sentence

"As the temperature gradually rose some 10,000 years ago ... "

GRADUAL means changes of a few tenths of a degree celsius over hundreds or thousands of years. We are seeing that same change in a generation. THATS the difference. THATS what tells us this current warming trend is anthropogenic.

Take a look again at this graph:



Notice how CO2 is stable until the industrial age? Then what happened? It shot up. It now stands at 393. That is a 40% increase in atmospheric CO2 which came about in 200 years. That aint natural.



Over the last 150 years, the average global temperature has increase by nearly a full degree Celsius.



Once we start pumping CO2 into the atmosphere, temp shoots up. See all the different colors? That indicates multiple sources, multiple studies, and multiple matching results.

The conclusion of the worlds scientific community is clear: global temperature is rising and human's have caused a large part of it by adding carbon dioxide to the atmosphere.

[mihalevich]

17. Environmental change is natural

And usually gradual. Life has time to evolve with the change. But when it's rapid and on a global scale, we get a mass extinction events like the KT event (Dinosaurs gone). We are going through a Mass Extinction now! I just found out that coral reefs will be gone soon?!?!