Ice Age Thawing And Carbon Dioxide Levels Linked In New Study

WASHINGTON (AP) — The dramatic temperature increases that thawed the last ice age followed spikes in carbon dioxide levels in the air, a new study finds. Researchers say that further strengthens the scientific case explaining current man-made global warming.

In the new study, scientists show the atmospheric concentration of that heat-trapping greenhouse gas jumped more than 40 percent. Then global temperatures went up about 6 degrees Fahrenheit (3.5 degrees Celsius).

What is remarkable is that when the two are plotted they rise, plateau and rise again in a striking similar way with a slight lag. The warming over 6,000 years follows the greenhouse gas increase, just as scientific theory has long held.

This is important because, until this study, the two curves weren't quite so in sync. At some points, it seemed that the temperatures warmed before the carbon dioxide levels increased, something that climate skeptics seized upon.

How could carbon dioxide cause warming if the temperatures warmed first, argue skeptics, who are in the scientific minority.

Earlier studies had looked at carbon dioxide levels and temperature readings from Antarctica, not the entire world. A study published Wednesday in the journal Nature estimated global temperatures using 80 different proxies — ice and mud samples from dozens of places around the world — and found that globally, temperatures clearly went up only after carbon dioxide jumped.

"You end up with something that looks remarkably similar to the pattern of rising carbon dioxide through time," study lead author Jeremy Shankun of Harvard University said. "This, to me, seems like pretty powerful proof of theory of the connection between greenhouse gases and global warming."

There are two main sources of carbon dioxide, the chief greenhouse gas. The natural source comes mostly from dead plants and animals and that amplified the ice age thaw. In modern day, emissions from burning coal, oil and other fossil fuels add greatly to that natural carbon dioxide.

The ice age warming in Antarctica still appears to come before the carbon dioxide increases, which are calculated using an 800,000 year old Antarctic ice core, but there's good reason, Shankun said.

Temperature records and other ocean data paint a complicated picture of just how the last ice age thawed. It's almost like a Rube Goldberg machine, with one step leading to another and another. When the last ice age peaked about 25,000 years ago, the ice sheet extended to Iowa and New York City, Shankun said.

The ice sheet was actually so large that it was unstable, said study co-author Peter Clark of Oregon State University.

The initial trigger to the melt: A small and predictable wobble in Earth's orbit around the sun. That tiny wobble meant a tilt toward the sun that brought more sunlight in the Northern Hemisphere, causing ice sheets to melt and sending whopping levels of fresh water into the world's oceans.

That caused the global circulation of the oceans to stop, which in turn warmed the southern oceans, melting southern ice sheets over areas where more of the world's carbon dioxide is trapped, Shankun said.

That released massive amounts of the greenhouse gas, which then amplified the global temperature spike, Shankun said.

By 11,000 years ago, the ice age was history and greenhouse gas and temperature levels had stabilized. That changed with the industrial age and the increased use of fossil fuels.

Carbon dioxide levels have jumped roughly the same amount in the last century as they did over 6,000 years to get out of the ice age, Shankun said.

Penn State University professor Richard Alley and others called this a significant advance in studies about past climate change and carbon dioxide, saying "this may be of help in explaining things out in the sound-bite world."

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Online:

Nature: http://www.nature.com/nature

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Comments

[Kenz300]

04:28 PM on 04/16/2012

The price of wind and solar have dropped by over 50% in the past few years while the cost of oil, coal and nuclear keep rising.

It is time to transition to safe, clean alternative energy sources.

[old soil guy]

06:53 PM on 04/08/2012

Good comments folks. As a soil scientist I'm used to making observations in the field. So I have personal, although considered anecdotal, conclusions that things are changing. Anecdotal because these only cover subtle changes in plants and animals over the last 30 years. And other small things, like we used to have our common area mowed twice a year, now it's been several years of just once. That means we are not getting as much July and August rain, though we still get the same annual total of 14 inches total precip (including snow, and now more winter rain).

If the information in this article is shown to be supported by the data, and appears it is, the climate change deniers will have to find another argument. And they will.

[maxwells]

02:04 PM on 04/09/2012

Old Soil Guy, hate to use repurpose your post, but Re: ceasar200 immediately below,

AKA netdr, aka HoosierDaddy25, aka leesburg-larry, aka NGC2623, aka Ptolemy101, aka neptune2, aka Texas-Titan, aka texas-husker, before he gets banned for the 11th time for relentless lying, even about what people say to him in response,

he's really the best evidence that ASTROTURFING exists right here on Huffington Post.

The only thing better would be for him to divulge who really funds him.

For who but a paid PR pro would continue to write ~2,800+ relentlessly lying comments (up to 70+ per day, clearly a full-time job) all in less than 5 months, EXCLUSIVELY on climate change, even while getting banned 10 times?

Moreover, he's also claimed:

"Actually I am a college professor."
http://www.huffingtonpost.com/social/netdr/farm-bill-climate-change-crop-insurance-subsidies_n_1146058_123792610.html
And
"I have a BSEE and have created computer models professionally for several years."

http://www.huffingtonpost.com/social/netdr/farm-bill-climate-change-crop-insurance-subsidies_n_1146058_123797495.html

What college hires BSers as profs who post 70 off-subject comments a day?

And why can't this self-proclaimed modeling "expert" answer some simple climate modeling questions?

http://www.huffingtonpost.com/social/maxwells/green-group-urges-gm-to-s_n_1321940_139711436.html

"college prof" or lying professional shill?

[GSR]

10:26 PM on 04/21/2012

Maxwell do you have no compassion?

Ceasar200..(AKA netdr, aka HoosierDaddy25, aka leesburg-larry, aka NGC2623, aka Ptolemy101, aka neptune2, aka Texas-Titan, aka texas-husker) is no longer with us.
I sure hope he had time to attach a screen shot of his short lived comment to his invoice. He's gonna have trouble paying his rent this week because of you. You should be ashamed of yourself.
Well done.

[trumphent]

09:25 AM on 04/06/2012

The summation of the article sounds like a verification of the science to me. The only surprise to me was the instability of ice sheets due to their sheer size. Even that makes sense after some thinking. Ice on earth has been described as a metallic crystal, very near its melting point. Ice can get to be as tough as steel if you get it as cold as Pluto. Ice sheets can suddenly disintegrate. And there are still people who wonder why the scientists that understand this are so concerned.

[RebelRyder]

12:12 AM on 04/06/2012

What an utter crock. CO2 does not drive temperature.

http://theinconvenientskeptic.com/2011/03/co2-and-global-temperature/

[jimboy71]

04:17 PM on 04/06/2012

So what, in your learned opinion, keeps the planet from freezing, if not CO2?

[RebelRyder]

04:55 PM on 04/06/2012

Water vapor.

http://hockeyschtick.blogspot.com/2012/03/water-vapor-not-co2-controls-climate.html

[Katmandu01]

05:13 PM on 04/06/2012

The greenhouse gas qualities of carbon dioxide have been known for over a century. In 1861, John Tyndal published laboratory results identifyin­­­­­­­­­­­­­­­­­­­­­­­­­­g carbon dioxide as a greenhouse gas that absorbed heat rays (longwave radiation)­­­­­­­­­­­­­­­­­­­­­­­­­­. Since then, the absorptive qualities of carbon dioxide have been more precisely quantified by decades of laboratory measuremen­­­­­­­­­­­­­­­­­­­­­­­­­­t­­s (Herzberg 1953, Burch 1962, Burch 1970).
http://www.opticsinfobase.org/josa/abstract.cfm?uri=josa-43-11-1037
http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-1-6-759
http://www.stormingmedia.us/49/4989/0498907.html
Human CO2 emissions upset the natural balance of the carbon cycle. Man-made CO2 in the atmosphere has increased by a third since the pre-indust­­­­­­­­­­­­­­­­­­­­­­­­­­r­­i­­a­­­l era, creating an artificial forcing of global temperatur­­­­­­­­­­­­­­­­­­­­­­­­­­e­­s which is warming the planet. While fossil-fue­­­­­­­­­­­­­­­­­­­­­­­­­­l derived CO2 is a very small component of the global carbon cycle, the extra CO2 is cumulative because the natural carbon exchange cannot absorb all the additional CO2. As well there is plenty of credible evidence to prove that temperatur­­­­­­­­­­­­­­e­s have and are continuing to be affected by CO2 levels.
http://books.nap.edu/openbook.php?record_id=11676&page=R1
And no. What's happening now is not within normal variations­­­­­­.
http://pubs.giss.nasa.gov/abs/ha05510d.html

[Jim Milks]

06:04 PM on 04/05/2012

The worrying part? A 40% rise in CO2 created a 3.5ºC rise in global temperatures. That implies a climate sensitivity of ~7.21ºC per doubling of CO2. Uh oh.

Note: Edited on 4/9/12 to give the correct climate sensitivity after I found a small error in my original calculations (originally reported a 7.16ºC value).

[grappler1987]

09:30 PM on 04/05/2012

Neat observation. James Hansen estimates 6 degrees C for CO2 doubling which is close enough to 7 degrees as you show.

http://pubs.giss.nasa.gov/docs/2008/2008_Hansen_etal.pdf

There are a couple things confusing about the "3 degrees for doubled CO2" factoid.

1) That is only for fast feedback (decades to century). Long term feedback is much greater (centuries to 1000 years). Hansen estimates 6 degrees over many centuries.

2) The fast feedback estimate is the output of a logrithmic equation that is a function of the starting point. I believe 280 ppm is used for the starting point (or something close) to get the 3 degrees for double CO2 (560 ppm). When looking at the ice age, the starting point was closer to 200 ppm. The "3 degree" reference just doesn't apply.

Your 7 degree C estimate seems awefully close to Hansen's estimate. Hansen did use paleoclimate data to reach his conclusion, which is not a stretch from what you did.

[Jim Milks]

12:05 PM on 04/08/2012

Sorry it took so long to reply. I just wanted to comment on your point 2. I used the same logarithmic equation to estimate climate sensitivity per doubled CO2. My calculations went like this:

Radiative forcing (ΔF) = 5.35 W/m^2 * ln(C/Co), where C is current CO2, Co is the starting point. In this case, C = Co + 0.4(Co), so the equation becomes 5.35 W/m^2 * ln(1.4) = 1.80 W/m^2.

Climate sensitivity (λ) = ΔT/ΔF = 3.5ºC/1.80 W/m^2 = 1.94 ºC/W/m^2

And of course, ΔF for doubled CO2 = 5.35 W/m^2 * ln(2Co/Co) = 3.71 W/m^2

So the expected temperature change with that value of λ for doubled CO2 is

ΔT = 1.94ºC/W/m^2 * 3.71 W/m^2 = 7.2ºC (rounded).

[grappler1987]

01:50 PM on 04/05/2012

"The dramatic temperature increases that thawed the last ice age followed spikes in carbon dioxide levels in the air, a new study finds."

conflicts with:

"The initial trigger to the melt: A small and predictable wobble in Earth's orbit around the sun. ... more sunlight in the Northern Hemisphere" ... "That caused the global circulation of the oceans to stop, which in turn warmed the southern oceans, melting southern ice sheets over areas where more of the world's carbon dioxide is trapped" ... "That released massive amounts of the greenhouse gas"

I think the study is saying that CO2 increases amplified temperature after the Ice Age ended, but it was the decline of the ice sheets that release the CO2.

Very confusing.

[Shan Wells]

04:25 PM on 04/05/2012

No.

1. Earth wobbles.
2. More sunlight hits northern hemisphere.
3. Ice sheets melt in northern hemisphere.
4. Freshwater hits northern Atlantic
5. Ocean currents cease circulating.
6. Souther oceans warm as a result.
7. Southern ice sheets thaw, releasing massive amount of Co2.
8. Co2 and other greenhouse gasses collect.
9. Feedback releases yet more gasses, causing ice age to retreat worldwide.
10. World temps wind up 6 degree higher before stabilizing.
11. All this happens over 6 thousand years.

And the kicker- the amount of Co2 released over 6 thousand years before is the same as the amount released in the last 100 years.

[grappler1987]

04:40 PM on 04/05/2012

Thanks for clearing that up. The article should have used bullets.

What does the article mean by this, ""The dramatic temperature increases that thawed the last ice age followed spikes in carbon dioxide levels in the air, a new study finds"?

Your bullets suggest that the ice sheets thawed by bullet 7 and the massive CO2 release occurred, which is inverted from the quote.

[grappler1987]

05:15 PM on 04/05/2012

BTW -- Your bullets present a paradox.

First, the northern hemisphere thaws (bullet 3).
Second, the southern hemisphere thaws (bullet 7).
Third, massive CO2 is released (bullet 7).
Fourth, the world thaws. (bullet 9).

A non-English speaking person might think a sphere has more than two hemispheres. In short, CO2 release follows and precedes worldwide thawing. The first paragraph in the article neglects the temperature increase that initiated the process. Maybe that was simple due to expediency.

[Publicola]

10:08 PM on 04/04/2012

U.S. National Academy of Sciences (2010)
------------------------------------------------------------------------

There is a strong, credible body of evidence, based on multiple lines of research, documenting that climate is changing and that these changes are in large part caused by human activities. While much remains to be learned, the core phenomenon­, scientific questions, and hypotheses have been examined thoroughly and have stood firm in the face of serious scientific debate and careful evaluation of alternative explanation­s…

From a philosophical perspective, science never proves anything… because science is fundamentally based on observations. Any scientific theory is thus, in principle, subject to being refined or overturned by new observations.

In practical terms, however, scientific uncertainties are not all the same. Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.

http://www.nap.edu/openbook.php?record_id=12782

[themodernleader]

06:08 AM on 04/05/2012

  F&F.  Written in bureaucratic language, the evidence proves up the conclusion that human activity is a major cause of the warming of the earth, the release of carbon dioxide locked in the Arctic permafrost, the melting of the icecaps, the rise of ocean levels and the variability of weather.  From this conclusion there is no long stretch in asserting that the earth way over populated with human kind.  I make a flat assertion that the human population of 7 billion is twice as large as is sustainable assuming a standard  of living of advanced industrial nations.  There should be international debate and action before life  is regarded as an  environmental hazard..

[johnhart44]

10:42 PM on 04/05/2012

I agree with your indictment of overpopulation as a major contributor to global warming as well as a host of other ills. But doing anything about it is anathema to just about every important religious, economic and political player in global decision making, so we are left hoping that the demographic transition works out, since no one in power will be willing to pay the price for advocating for serious population control measures. Just imagine how much worse off the world would be now if China hadn't instituted their one child policy in the 1970s.

[silverwolf13]

06:34 PM on 04/04/2012

When deniers find both fact and theory against them, they pound the table and call names. Ho-hum.