As Ice Age ended, greenhouse gas rise was lead factor in melting of Earth's glaciers

August 21, 2015
Improved dating methods reveal that the rise in carbon dioxide levels was the primary cause of the simultaneous melting of glaciers around the globe during the last Ice Age. The new finding has implications for rising levels of man-made greenhouse gases and retreating glaciers today. Credit: National Science Foundation

A fresh look at some old rocks has solved a crucial mystery of the last Ice Age, yielding an important new finding that connects to the global retreat of glaciers caused by climate change today, according to a new study by a team of climate scientists.

For decades, researchers examining the glacial meltdown that ended 11,000 years ago took into account a number of contributing factors, particularly regional influences such as solar radiation, ice sheets and ocean currents.

But a reexamination of more than 1,000 previously studied glacial boulders has produced a more accurate timetable for the pre-historic meltdown and pinpoints the rise in - then naturally occurring - as the primary driving factor in the simultaneous global retreat of glaciers at the close of the last Ice Age, the researchers report in the journal Nature Communications.

"Glaciers are very sensitive to temperature. When you get the world's glaciers retreating all at the same time, you need a broad, global reason for why the world's thermostat is going up," said Boston College Assistant Professor of Earth and Environmental Sciences Jeremy Shakun. "The only factor that explains glaciers melting all around the world in unison during the end of the Ice Age is the rise in greenhouse gases."

The researchers found that regional factors caused differences in the precise timing and pace of glacier retreat from one place to another, but carbon dioxide was the major driver of the overall global meltdown, said Shakun, a co-author of the report "Regional and global forcing of glacier retreat during the last deglaciation."

"This is a lot like today," said Shakun. "In any given decade you can always find some areas where glaciers are holding steady or even advancing, but the big picture across the world and over the long run is clear - carbon dioxide is making the ice melt."

While 11,000 years ago may seem far too distant for a point of comparison, it was only a moment ago in geological time. The team's findings fix even greater certainty on scientific conclusions that the dramatic increase in manmade will eradicate many of the world's glaciers by the end of this century.

"This has relevance to today since we've already raised CO2 by more than it increased at the end of the Ice Age, and we're on track to go up much higher this century—which adds credence to the view that most of the world's glaciers will be largely gone within the next few centuries, with negative consequences such as rising sea level and depleted water resources," said Shakun.

The team reexamined samples taken from boulders that were left by the retreating glaciers, said Shakun, who was joined in the research by experts from Oregon State University, University of Wisconsin-Madison, Purdue University and the National Center for Atmospheric Research in Boulder, Colo.

Each boulder has been exposed to cosmic radiation since the glaciers melted, an exposure that produces the isotope Beryllium-10 in the boulder. Measuring the levels of the isotope in boulder samples allows scientists to determine when glaciers melted and first uncovered the boulders.

Scientists have been using this process called surface exposure dating for more than two decades to determine when glaciers retreated, Shakun said. His team examined samples collected by multiple research teams over the years and applied an improved methodology that increased the accuracy of the boulder ages.

The team then compared their new exposure ages to the timing of the rise of in the atmosphere, a development recorded in air bubbles taken from ice cores. Combined with computer models, the analysis eliminated regional factors as the primary explanations for glacial melting across the globe at the end of the Ice Age. The single leading global factor that did explain the global retreat of glaciers was rising carbon dioxide levels in the air.

"Our study really removes any doubt as to the leading cause of the decline of the glaciers by 11,000 years ago - it was the rising levels of carbon dioxide in the Earth's atmosphere," said Shakun.

Carbon dioxide levels rose from approximately 180 parts per million to 280 parts per million at the end of the last Ice Age, which spanned nearly 7,000 years. Following more than a century of industrialization, carbon dioxide levels have now risen to approximately 400 parts per million.

"This tells us we are orchestrating something akin to the end of an Ice Age, but much faster. As the amount of carbon dioxide continues to increase, around the world will retreat," said Shakun.

Explore further: Climate change not so global

Related Stories

Climate change not so global

August 4, 2014

(Phys.org) —Scientists are calling for a better understanding of regional climates, after research into New Zealand's glaciers has revealed climate change in the Northern Hemisphere does not directly affect the climate ...

The ebb and flow of Greenland's glaciers

June 1, 2015

In northwestern Greenland, glaciers flow from the main ice sheet to the ocean in see-sawing seasonal patterns. The ice generally flows faster in the summer than in winter, and the ends of glaciers, jutting out into the ocean, ...

Glaciers melt faster than ever

August 3, 2015

The World Glacier Monitoring Service, domiciled at the University of Zurich, has compiled worldwide data on glacier changes for more than 120 years. Together with its National Correspondents in more than 30 countries, the ...

Recommended for you

Did meteorites bring life's phosphorus to Earth?

August 30, 2016

Meteorites that crashed onto Earth billions of years ago may have provided the phosphorous essential to the biological systems of terrestrial life. The meteorites are believed to have contained a phosphorus-bearing mineral ...

28 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Ultron
1.6 / 5 (20) Aug 21, 2015
Very poor study. It is not clearly stated if the rise of CO2 was before the ice started to melt or the CO2 level has risen along as ice melted.
And this article didnt mention what has caused the rise of CO2 long before humans had started to increase it.
It also opens important question, if CO2 was really the starter of ice melting, was the start of glacial period also marked by decreased CO2 level or was there other cause for start of glacial period?
docile
Aug 21, 2015
This comment has been removed by a moderator.
zz5555
4.2 / 5 (21) Aug 21, 2015
Very poor study. It is not clearly stated if the rise of CO2 was before the ice started to melt or the CO2 level has risen along as ice melted.
And this article didnt mention what has caused the rise of CO2 long before humans had started to increase it.
It also opens important question, if CO2 was really the starter of ice melting, was the start of glacial period also marked by decreased CO2 level or was there other cause for start of glacial period?

Science, at it's best, is a collaborative effort. Many scientists contribute one small piece to the puzzle. It is exceedingly rare to find any one paper that answers all questions. This one answers just one part. Other studies have shown that the rise in CO2 preceded the warming (and melting). There are many candidates for the change in CO2 - changes in ocean circulation are probably the most likely. As for the start of glaciation, search for Milankovitch cycles.
denglish
1.6 / 5 (7) Aug 21, 2015
I tried to find the paper, and I got this:
http://www.nature...059.html

Is that the right one?
Ultron
1.5 / 5 (16) Aug 21, 2015
Milankovich cycles were considered as cause for glacial period, but it was not confirmed. Just look wikipedia. We dont know, what is causing glacial periods.
runrig
5 / 5 (13) Aug 21, 2015
Milankovich cycles were considered as cause for glacial period, but it was not confirmed. Just look wikipedia. We dont know, what is causing glacial periods.

Yes, we do.
Read it again.
Ice ages correlate with M cycles.
It is the exact mechanism as to how they do that is not clear and the dominance in recent geological history of the 100kyr cycle.
It is still thought that TSI at 65N is the controlling factor.
Don't forget the Earth has changed geologically over these times scales.
There are feed-back mechanisms that have to come into play, Vis ocean currents.

https://en.wikipe.../Ice_age
plasmasrevenge
1 / 5 (16) Aug 21, 2015
Re: "The only factor that explains glaciers melting all around the world in unison during the end of the Ice Age is the rise in greenhouse gases."

Like many studies today purporting to make a claim about what has happened in the past, all of the techniques used to make these claims depend very heavily upon the uniformitarian assumption -- this notion that we can simplistically determine what happened in the past by simply observing the present.

ALL dating methodologies require strict adherence to uniformitarianism because any sort of large-scale event would be expected to scramble the very dates we use to postulate the event.

So, when researchers make this claim above, realize that they already necessarily adopted the assumption that transient events cannot be the cause for their observations of retreating glaciers.

People no longer even track the assumptions that go into the former claims; they simply build upon them, creating a mountain of nonsense.
Vietvet
4.5 / 5 (16) Aug 21, 2015
claims depend very heavily upon the uniformitarian assumption -- this notion that we can simplistically determine what happened in the past by simply observing the present.

Your ignorance is showing.

Ultron
1 / 5 (11) Aug 21, 2015
Cant you read people or what?

The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age.

https://en.wikipe.../Ice_age
runrig
5 / 5 (13) Aug 21, 2015
Cant you read people or what?

The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age.

https://en.wikipe.../Ice_age

"The consensus is that several factors are important: atmospheric composition, such as the concentrations of carbon dioxide and methane (the specific levels of the previously mentioned gases are now able to be seen with the new ice core samples from EPICA Dome C in Antarctica over the past 800,000 years; changes in the earth's orbit around the Sun known as Milankovitch cycles; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on the earth's surface, which affect wind and ocean currents; variations in solar output; the orbital dynamics of the Earth-Moon system; and the impact of relatively large meteorites, and volcanism including eruptions of supervolcanoes
Bongstar420
1 / 5 (7) Aug 21, 2015
Don't warming oceans release CO2?

What of the rate of undersea volcanism?
Da Schneib
4.4 / 5 (14) Aug 21, 2015
Very poor study.
Very poor review. One star and addition to my ignore list.
greenonions
5 / 5 (12) Aug 21, 2015
Ultron
Cant you read people or what?


Did you notice the word "fully?" Also - Wikipedia is not necessarily the final word on any subject. A quick google search will show you that we do have a level of understanding of the drivers of ice ages.

http://geology.ut...es-them/
ColoradoBob
2.7 / 5 (12) Aug 24, 2015
Fastest moving glacier in the world sheds 12.5 sq km chunk of ice

The image time series suggests that between 27 July and 13 August, the glacier advanced westward before the calving caused rapid retreat of the ice front to its position on 19 August.

It is estimated that the glacier lost a total area of 12.5 sq km. Assuming the ice is about 1400 m deep, this equates a volume of 17.5 cubic km %u2013 which could cover the whole of Manhattan Island by a layer of ice about 300 m thick.

http://phys.org/n...-km.html
jeffensley
4.3 / 5 (6) Aug 24, 2015
Fastest moving glacier in the world sheds 12.5 sq km chunk of ice

The image time series suggests that between 27 July and 13 August, the glacier advanced westward before the calving caused rapid retreat of the ice front to its position on 19 August.

It is estimated that the glacier lost a total area of 12.5 sq km. Assuming the ice is about 1400 m deep, this equates a volume of 17.5 cubic km %u2013 which could cover the whole of Manhattan Island by a layer of ice about 300 m thick.

http://phys.org/n...-km.html


Bet that made a nice wave.
Shootist
1 / 5 (6) Aug 25, 2015
The "Ice Age" has not ended. We are merely between glaciations.
AGreatWhopper
1.7 / 5 (12) Aug 25, 2015
AGWites really don't get how they fuel all these idiot tin hat jobs. What's cheerleader in chief doing today? http://www.thegua...58167420 HYPOCRITES.

The biggest thing fueling deniers is that those that are beating the AGW drum don't act one bit different than the deniers. LAS FREAK'IN VEGAS??? The most unsustainable city on the planet. That's a good place to kick back. Do they breed less than deniers? Drive less? Use less petroleum? Quit their job, sell their house and move to more sustainable places? No. Yell how "THEY have to change" but do not one thing yourself. Oh, buy green. Yeah, the consumerist mindset isn't *much* a part of the problem.
AGreatWhopper
1.7 / 5 (11) Aug 25, 2015
If my house is on fire, I would act like it. If I yelled out the windows desperately for the neighbors to help, then sat down and went back to reading a book, I think that might make the neighbors skeptical about my plight. That's what too many are doing with climate change. Preach how it's the biggest challenge of our times...and then go on living with the same assumptions that our parents and the deniers do. Top of that class has to be Pope Francis. Talk sincerely about addressing climate change, but don't let people use birth control.

Deniers exist because of the MONUMENTAL hypocrisy of those that accept the hypothesis.
jim_xanara
1.5 / 5 (8) Aug 25, 2015
Skeptics exist because not everyone is in the thrall of the Rockefeller Foundation and the Council for Foreign Affairs and the internatinal banking cabal. I'll bet none of the skeptics on here are circumcized. Being skeptical about that culture starts at birth. The rest of you literally have your loyalty carved in your flesh.
jljenkins
1 / 5 (5) Aug 25, 2015
Obama's the biggest hypocrite going. The article cited by AGW has him decrying the influence of money in politics. So, what did he do the day after the Supremes ruled that money in politics effectively has no limits? Signed an executive order making it a crime to crowd source a Presidential candidate. His idea of being fair is to keep everyone equally pissed off.
AGreatWhopper
1.4 / 5 (9) Aug 25, 2015
What about as Horizon was gushing oil, he was signing more leases for BP to drill even deeper in the Gulf? When some started to find out he signed an executive order making the leases classified. I got a number of liberals to vote their conscience and not their party last time by betting them anything they wanted and assuring them that they shouldn't be thinking about Mitt Romney, they should be thinking about how they would feel the day he allowed drilling in the ANWR, that they had voted for him. Have had a few this week come back with, "Yeah, it's not throwing away your vote, it's saving your soul".

Not that the usual liberal hypocrite gang bangers care about principles. Decide on an a priori conclusion, work backwards cherry picking data and leave out what doesn't fit. I can't imagine how the deniers learned that.
denglish
1 / 5 (4) Aug 25, 2015
Skeptics gain their power from the observations not meeting predictions, evidence that the earth is not experiencing anything unusual in its cyclic change variation boundaries, and the discovery of more and more of the earth's climate machinations on what seems to be an almost weekly basis.

Pointing to hypocrisy or other political low-hanging fruit as proof plays into populism, not science, is a double edged sword, and doesn't get anyone anywhere.
HeloMenelo
2.5 / 5 (8) Aug 27, 2015
I tried to find the paper, and I got this:
http://www.nature...059.html

Is that the right one?


a...aaaa, no monkey, try harder, grip the branch with both hands firmly, then you can swing... ;)
HeloMenelo
2.5 / 5 (8) Aug 27, 2015
Cant you read people or what?
...
http://https://en.wikipe.../Ice_age

"The consensus is that several factors are important: atmospheric composition, such as the concentrations of carbon dioxide and methane (the specific levels of the previously mentioned gases are now able to be seen with the new ice core samples from EPICA Dome C in Antarctica over the past 800,000 years; changes in the earth's orbit around the Sun known as Milankovitch cycles; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic cruss

oops ultron...aka denglish got hand full of horsepoo in the face... again :D
HeloMenelo
2.5 / 5 (8) Aug 27, 2015
The "Ice Age" has not ended. We are merely between glaciations.


Nope, The climate is warming, so is the yellow stuff you shot onto yourself when you aim went skew for the potty ;)
antigoracle
1 / 5 (4) Aug 27, 2015
You gotta love AGW Cult "science". Anything to propagate their dogma.
HeloMenelo
2.1 / 5 (7) Aug 28, 2015
You gotta love AGW Cult "science". Anything to propagate their dogma.


Gotta love the humour in a gorilla showing his one braincell view to the world... where's your puppet donglish, in the washing... ? Not surprisingly as the smell from your hands is horrendous from wearing that sock day and night all year long :D
HeloMenelo
2.1 / 5 (7) Aug 28, 2015
Aaa ?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.