Warming 'seesaw' turns extra sunlight into global greenhouse

Feb 07, 2013 by Chris Barncard
As Earth’s orbit brought it close to the sun more than 20,000 years ago, intense summer rays melted Northern Hemisphere glaciers, like this one in Greenland. Computer climate models have confirmed theories that the meltwater pouring into the ocean began a "bipolar seesaw" of forces that warmed the entire globe. Credit: Kelsey Winsor, UW–Madison

(Phys.org)—Earth's most recent shift to a warm climate began with intense summer sun in the Northern Hemisphere, the first pressure on a seesaw that tossed powerful forces between the planet's poles until greenhouse gases accelerated temperature change on a global scale.

, led by a group from the University of Wisconsin-Madison, used computer models to provide the strongest support yet to a case made nearly 90 years ago by mathematician Milutin Milankovitch.

"Milankovitch actually calculated the changes in insolation—the amount of heat coming into the from sunlight—in the by astronomy," says Feng He, a scientist at UW-Madison's Center for Climatic Research. "He did that before World War I, and that equation is still fairly accurate, even though he didn't have anything like the computing resources we do."

Milankovitch's work showed glacial rise and decline tied to cycles of summer sun—as opposed to winter conditions, which were intuitively expected to hold sway. A glacier that could survive summer without substantial ice loss was well set to grow even during sunny winters.

The importance of summer sun has been confirmed repeatedly by studies of physical , largely ice and taken from glaciers and the bottom of oceans around the world. But the progression of —from north to south, or south to north—during the last great glacial melt about 20,000 years ago is hard to follow, and has proven a bone of contention among those studying .

Using a version of the computer model of the Earth's climate used by the United Nations Intergovernmental Panel on Climate Change, He and collaborators have reproduced that global warming environment as a series of falling dominoes at opposite ends of the Earth.

"That insolation in the north is the trigger," says He, whose work will be published tomorrow (Feb. 7, 2013) in the journal Nature. "But the first consistent warming comes in the Southern Hemisphere, and that warming releases carbon dioxide into the atmosphere. The CO2 is the feedback that accelerates the warming and gets the whole world into full deglaciation."

The intersection of a pair of cyclical quirks in the Earth's orbit—one that brings it closest to the sun every 21,000 years, and another that tilts its poles closest to the sun every 41,000 years—made for particularly powerful sunshine on an icy Northern hemisphere.

The researchers added Northern Hemisphere glacial melt to the IPCC and ran it through the period of the last major glacial melt repeatedly on supercomputers at the Department of Energy's Oak Ridge National Laboratory.

Model runs revealed the overturning current as key to what the researchers, whose work was funded by the National Science Foundation, called a bipolar seesaw.

Increasing sunlight alone wasn't enough to melt the northern glaciers, but enough freshwater runoff spilled into the ocean to disrupt the progression of the overturning current, which carries warm water from the southern Atlantic Ocean and returns cooler water south. Without a way to ship heat north, the Southern Hemisphere began to warm.

"When the melt water enters the ocean, it triggers the Southern Hemisphere warming, the retreat of southern sea ice, and maybe the warming of the deep ocean and circulation changes," He says. "All of this extracts CO2 from the southern oceans, and it's that change that leads to a global greenhouse atmosphere and a speeding-up of the warming process around the world."

That global temperature shift pushed even the Northern Hemisphere's glaciers into decline, and the planet into the moderate climate it enjoys today.

"This is the first study to show this mechanism reproduced to account for early deglacial warming of the , He says. "Before, people were using this mechanism for abrupt climate change events, but we are showing this mechanism accounts for slower, lasting warming as well."

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User comments : 17

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VendicarE
3 / 5 (14) Feb 07, 2013
Where are all the Denialist Tards?

Here Tardie, Tardie, Tardie, Tardie...
Here Tardie, Tardie, Tardie, Tardie...
Here Tardie, Tardie, Tardie, Tardie...
Here Tardie, Tardie, Tardie, Tardie...
Here Tardie, Tardie, Tardie, Tardie...

There's a good little Tard...
tpb
1.5 / 5 (15) Feb 07, 2013
Well, here's one.
It was increases in insolation caused by changes in earths orbit and earths tilt that caused the warming. Nothing in this article says that the CO2 we put into the atmosphere is capable of this without the increase in solar energy.
rubberman
3.8 / 5 (13) Feb 07, 2013
Well, here's one.
It was increases in insolation caused by changes in earths orbit and earths tilt that caused the warming. Nothing in this article says that the CO2 we put into the atmosphere is capable of this without the increase in solar energy.


The call goes out...and they show up.

From the article: "All of this extracts CO2 from the southern oceans, and it's that change that leads to a global greenhouse atmosphere and a speeding-up of the warming process around the world."

Regardless of the source of the CO2, the effect is the same. In our case the north has warmed more initially, considering the bulk of anthropogenic CO2 is produced in the Northern Hemisphere I would say this only solidifies the correlation. Identification of the way the "natural" mechanism works compared to what is happening today evidences humanities contribution even more.
VendicarE
3.7 / 5 (12) Feb 07, 2013
Of course, the slow 120,000 year variation in the earth's orbital and rotational parameters magically caused global temperatures to remain generally static over the last 12,000 years and then suddenly produce a 1/C temperature spike over a period of around 100 years.

"It was increases in insolation caused by changes in earths orbit and earths tilt that caused the warming." - tpb

Probability = 0.0
djr
3.9 / 5 (8) Feb 08, 2013
"The call goes out...and they show up." That is right after they have been watching Fox news. Anatalias and other Germans will love this one - did you know that Germany has more sun than the U.S.? This is why their solar industry is doing so well - and the U.S. is doomed to burn fossil fuels for ever - it's the truth - the Fox business reporter has done her homework you know!

http://mediamatte...y/192568
djr
4.3 / 5 (6) Feb 08, 2013
Lawrence Krauss understands the source of a lot of this nonsense.

http://www.youtub...dvV6oZjo
ubavontuba
1.7 / 5 (12) Feb 08, 2013
Of course, the slow 120,000 year variation in the earth's orbital and rotational parameters magically caused global temperatures to remain generally static over the last 12,000 years and then suddenly produce a 1/C temperature spike over a period of around 100 years.
LOL. Vendispambot thinks the climate has been perfectly stable for the last 12,000 years. LOL.

http://en.wikiped..._optimum

Try again.

The Alchemist
1.4 / 5 (5) Feb 08, 2013
Well at least it talks about insolation. Sigh. I mean really if the general public can cry the obvious foul, then hoe are these becoming publications.
NOW does everyone see why I don't trust work you can't do yourself? Why do you all think you can get out a piece of paper and figure this out yourselves?
I have an intuitive predictive model for climate that anyone can use... and yet...
@djr, wind power is the way to go... it's cheap, it's a generator sitting fourty feet over your roof (flagpole), it's a few batteries, and it's 1920's technology. The wind is pretty constant above 40 feet.
runrig
4.2 / 5 (5) Feb 09, 2013
wind power is the way to go... it's cheap, it's a generator sitting fourty feet over your roof (flagpole), it's a few batteries, and it's 1920's technology. The wind is pretty constant above 40 feet.

I know where you're coming from and I support the idea of local renewable power but in the UK having a wind generator at 40 ft at every house just is not possible even if planning allowed it, the things would be far to intrusive in such a densely packed population. I have a solar pv array, and what is needed is a method to store the power for use during the evening. Battery technology is the key.
RealScience
5 / 5 (2) Feb 09, 2013
Battery technology is the key

@runrig - It would be safer to say "Storage technology is the key", as non-battery storage would also work.

(And even then, something like room-temperature superconductors could allow sufficiently broad geographic averaging of renewables to reduce the needs for storage to where our current hydroelectric dams would be sufficient.)
VendicarE
4.2 / 5 (5) Feb 09, 2013
From UbVonTard's own reference...

http://upload.wik...ions.png

"LOL. Vendispambot thinks the climate has been perfectly stable for the last 12,000 years" - UbVonTard

Looks pretty stable to me. But then VonTard has continually proven itself incapable of reading a graph.
The Alchemist
1 / 5 (2) Feb 09, 2013
Why is it so impossible to edit while writing?, I meant... how, not hoe &
NOW does everyone see why I don't trust work you can't do yourself? Why do you all think you can't get out a piece of paper and figure this out yourselves?

Apologies-TA
ubavontuba
1 / 5 (7) Feb 10, 2013
From Uba's own reference...

http://upload.wik...ions.png

"LOL. Vendispambot thinks the climate has been perfectly stable for the last 12,000 years" - Uba

Looks pretty stable to me. But then Uba has continually proven itself incapable of reading a graph.
LOL. Vendispambot doesn't understand the graph! He thinks the average represents the actual temperature data. LOL.

The black line is just an average of multiple data sets. It's so smoothed it can't resolve temperature fluctuations faster than approximately 300 years ...and it doesn't even appear until about 11,500 years ago! LOL.

Read about the graph, here:

http://en.wikiped...ions.png

Try again, Vendispambot.

VendicarE
4.2 / 5 (5) Feb 10, 2013
UbVonTard has no direct temperature data from 12,000 years ago, since no one has any. But we do have various proxies, and they don't support his earlier claims.

"LOL. Vendispambot doesn't understand the graph! He thinks the average represents the actual temperature data. LOL." - UbVonTard

His defense seems to be that there is no temperature data that disproves his claims, but then he has just admitted that there is no data to support his claims.

In reality of course, the best data we have, indicates that he is a chronic liar.

The graphic provided is ample evidence of this.

http://upload.wik...ions.png
ubavontuba
1 / 5 (5) Feb 10, 2013
Uba has no direct temperature data from 12,000 years ago, since no one has any. But we do have various proxies, and they don't support his earlier claims.

"LOL. Vendispambot doesn't understand the graph! He thinks the average represents the actual temperature data. LOL." - Uba

His defense seems to be that there is no temperature data that disproves his claims, but then he has just admitted that there is no data to support his claims.
LOL. Nice strawman you got going on here. Too bad it is you who made the claims! LOL! and Ha-ha-ha!

In reality of course, the best data we have, indicates that he is a chronic liar.

The graphic provided is ample evidence of this.

http://upload.wik...ions.png
And yes, the graph clearly proves the Vendispambot is wrong. ROFL.

hopper
2 / 5 (4) Feb 11, 2013
From the article: "All of this extracts CO2 from the southern oceans, and it's that change that leads to a global greenhouse atmosphere and a speeding-up of the warming process around the world." Regardless of the source of the CO2, the effect is the same. In our case the north has warmed more initially, considering the bulk of anthropogenic CO2 is produced in the Northern Hemisphere I would say this only solidifies the correlation. Identification of the way the "natural" mechanism works compared to what is happening today evidences humanities contribution even more.
.............
the problem with this analysis is that you have correlation you don't have causation--which is key. The problem with carbon dioxide being the cause is heating is not only that the sun is the cause of the initial heating .... but the sun is also the cause of the cooling that reverses the whole process and shrinks the carbon dioxide in the atmosphere.
Q-Star
1 / 5 (2) Feb 11, 2013
Lawrence Krauss understands the source of a lot of this nonsense.

http://www.youtub...dvV6oZjo


One of the best writers of popular science to come along in a long time. He does good, honest writing geared to help people get a fundamental grasp on some very difficult topics. And his original research over the years is superlative also. Particularly his papers in the 80's predicting an accelerating expansion and flat universe.