Ice core studies confirm accuracy of climate models

Sep 11, 2008

An analysis has been completed of the global carbon cycle and climate for a 70,000 year period in the most recent Ice Age, showing a remarkable correlation between carbon dioxide levels and surprisingly abrupt changes in climate.

The findings, to be published this week in the online edition of the journal Science, shed further light on the fluctuations in greenhouse gases and climate in Earth's past, and appear to confirm the validity of the types of computer models that are used to project a warmer climate in the future, researchers said.

"We've identified a consistent and coherent pattern of carbon dioxide fluctuations from the past and are able to observe the correlation of this to temperature in the northern and southern hemispheres," said Ed Brook, an associate professor of geosciences at Oregon State University. "This is a global, interconnected system of ocean and atmosphere, and data like these help us better understand how it works."

The analysis was made by studying the levels of carbon dioxide and other trace gases trapped as bubbles in ancient ice cores from Antarctica.

In the last Ice Age, as during most of Earth's history, levels of carbon dioxide and climate change are intimately linked. Carbon dioxide tends to rise when climate warms, and the higher levels of carbon dioxide magnify the warming, Brook said. These natural cycles provide a "fingerprint" of how the carbon cycle responds to climate change.

In contrast to the relatively low levels of carbon dioxide in the Ice Age, the burning of fossil fuels since the Industrial Revolution has led to levels of greenhouse gases that by comparison are off the charts. The level of atmospheric carbon dioxide today is about 385 parts per million, or more than double that of some of the lower levels during the Ice Age. These changes have taken place at a speed and magnitude that has not occurred in hundreds of thousands of years, if not longer. Past studies of ice cores have suggested that Earth's temperature can sometimes change amazingly fast, warming as much as 15 degrees in some regions within a couple of decades.

The question everyone wants to know is what all this will mean in terms of future climate change.

"Before humans were affecting the Earth, what we are finding is regular warm and cold cycles, which both began and ended fairly abruptly," Brook said. "This study supports the theory that a key driver in all this is ocean currents and circulation patterns, which create different patterns of warm and cold climates depending on the strength of various parts of the global ocean circulation system."

This issue is of more than academic interest – one of the primary circulation patterns is referred to scientifically as "meridional overturning circulation." When that current is moving large amounts of warm water from the equator to the north, it helps to warm the high latitude parts of the Northern Hemisphere, and particularly the North Atlantic region. When the system stops or dramatically slows, as it has repeatedly in the past, Greenland and Europe get much colder while the Antarctic regions become warmer, Brook said.

"In every historic sequence we observed, the abrupt warming of Greenland occurred about when carbon dioxide was at maximum levels," Brook said. "And that was during an Ice Age, and at levels of atmospheric carbon dioxide that are far lower than those we have today."

Source: Oregon State University

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jscroft
2.7 / 5 (16) Sep 11, 2008
The authors left out an absolutely critical detail: do changes in CO2 levels PRECEDE temperature changes, or not?

Correlation is necessary, but insufficient, to support the hypothesis that CO2 levels drive climate change. There is a powerful body of research to support the hypothesis that precisely the reverse is true: that changes in global CO2 levels are a CONSEQUENCE of climate change, rather than a CAUSE.

The actual timing of these events is critical to falsifying either hypothesis. Given that the authors appear to come down rather firmly on the side of CO2-driven climate change, one wonders why they didn't include the obviously relevant timing data.

Unless, of course, the timing data DON'T support their assertions... in which case one wonders what other agendas are in play.
GrayMouser
2.4 / 5 (14) Sep 11, 2008
The authors left out an absolutely critical detail: do changes in CO2 levels PRECEDE temperature changes, or not?


Actually they do say. The warming comes first:
"Carbon dioxide tends to rise when climate warms".

Where they fall flat on their face is the level of CO2. Historically it has been as high as 1800ppm without any help from humans.
deatopmg
2.1 / 5 (15) Sep 11, 2008
".. in which case one wonders what other agendas are in play."

C'mon - $$$$$$$$$$$$$$$$$$
GrayMouser
1.9 / 5 (9) Sep 13, 2008
".. in which case one wonders what other agendas are in play."

C'mon - $$$$$$$$$$$$$$$$$$


I'm afraid I must concur.
Rute
3 / 5 (8) Sep 13, 2008
Where they fall flat on their face is the level of CO2. Historically it has been as high as 1800ppm without any help from humans.

Not historically, but prehistorically. CO2 levels were very high in the Phanerozoic era, but the world was very different then.

There haven't been any supervolcano eruptions recently to explain the rise in CO2 levels naturally. Actually mankind produces more than 130 times more CO2 in the atmosphere from outside of the natural cycle than all volcanoes combined. Source: http://volcanoes....ndex.php (-> Effects, US Geological Survey)
Velanarris
3 / 5 (10) Sep 13, 2008
Where they fall flat on their face is the level of CO2. Historically it has been as high as 1800ppm without any help from humans.

Not historically, but prehistorically. CO2 levels were very high in the Phanerozoic era, but the world was very different then.

There haven't been any supervolcano eruptions recently to explain the rise in CO2 levels naturally. Actually mankind produces more than 130 times more CO2 in the atmosphere from outside of the natural cycle than all volcanoes combined. Source: http://volcanoes....ndex.php (-> Effects, US Geological Survey)


Yes but as late as the unification of Greece and rise of Roman the CO2 levels were supposed to be over 1000ppm by some models, and known to be over 700ppm by geological record. More than twice the current CO2 levels and all through natural processes.
Rute
4 / 5 (6) Sep 13, 2008
Yes but as late as the unification of Greece and rise of Roman the CO2 levels were supposed to be over 1000ppm by some models, and known to be over 700ppm by geological record. More than twice the current CO2 levels and all through natural processes.

Can you mention some peer-reviewed studies that support your claim?
Velanarris
2.3 / 5 (8) Sep 13, 2008
Yes but as late as the unification of Greece and rise of Roman the CO2 levels were supposed to be over 1000ppm by some models, and known to be over 700ppm by geological record. More than twice the current CO2 levels and all through natural processes.

Can you mention some peer-reviewed studies that support your claim?


Can you link some peer reviewed studies that support yours?
Rute
4.7 / 5 (10) Sep 14, 2008
Can you link some peer reviewed studies that support yours?

Here's data from the EPICA Dome C Ice Core (200 years before present to 21 000 years before present):
ftp://ftp.ncdc.no...-co2.txt

(That dataset is used in a peer reviewed study named "Historical CO2 records from the Law Dome DE08, DE08-2, and DSS ice cores" and many others.)

According to the dataset, the variation is between 260 and 280 ppmv. There's a huge number of ice core datasets that point to similar variation, such as Law Dome, Siple Dome, Vostok Dome and Taylor Dome, but I know none that would support your claim.

Do you know?
Bazz
2.4 / 5 (5) Sep 14, 2008
Good comeback rute.

Next there will come arguments about your agenda.



Velanarris
3 / 5 (6) Sep 14, 2008
Good comeback rute.

Next there will come arguments about your agenda.



Kudos on linking the study, very nice and appreciated.

Did you take a look at the dataset? Doesn't show much change from present concentrations (approx 280ppm now). How does this paper support your claim that CO2 concentration is driving global warming if the CO2 concentration shows no correlation with the warm and cold periods of the earth?
Rute
3.7 / 5 (7) Sep 14, 2008
Did you take a look at the dataset? Doesn't show much change from present concentrations (approx 280ppm now).

Huh? The current CO2 concentration in the atmosphere is about 380 ppmv. According to every dataset I know, including the one I mentioned, that's about 100 ppmv more than the concentration 200 years ago.
Velanarris
2.7 / 5 (7) Sep 14, 2008
Did you take a look at the dataset? Doesn't show much change from present concentrations (approx 280ppm now).

Huh? The current CO2 concentration in the atmosphere is about 380 ppmv. According to every dataset I know, including the one I mentioned, that's about 100 ppmv more than the concentration 200 years ago.


I've seen the current datasets vary wildly from 170ppm to 400 ppm. Global mean is 280ppm at the tropopause.
Bazz
3.7 / 5 (3) Sep 14, 2008
Those ice cores from the shallowest samples started 230years ago (173 before 1950)to 21000years ago for the deepest.
Rute
4.6 / 5 (5) Sep 14, 2008
Did you take a look at the dataset? Doesn't show much change from present concentrations (approx 280ppm now).

Huh? The current CO2 concentration in the atmosphere is about 380 ppmv. According to every dataset I know, including the one I mentioned, that's about 100 ppmv more than the concentration 200 years ago.


I've seen the current datasets vary wildly from 170ppm to 400 ppm. Global mean is 280ppm at the tropopause.

1. Just what datasets show concentrations of 170 ppm or even below 350 ppm?

2. What datasests were used to measure the global mean at tropopause and what is it's relevance to the low troposphere CO2 concentration measurements and reconstructions?
GrayMouser
2.3 / 5 (6) Sep 14, 2008
Where they fall flat on their face is the level of CO2. Historically it has been as high as 1800ppm without any help from humans.

Not historically, but prehistorically. CO2 levels were very high in the Phanerozoic era, but the world was very different then.


You missed the point. If the atmospheric CO2 levels were as high as 1800ppm
1) Why did the planetary temperature not rise to lethal levels for all life on the Earth?
2) If there is a critical point at which irreversible global warming takes place, how come we are not still that hot?

Ice cores have problems when using them as a proxy for temperatures. The gas levels in a Andean ice core can not be compared directly to the gas levels of an Antarctic or Greenland ice core. For some reason the processes that work in one way in the Antarctic work the reverse in the Andes.
http://www.nap.ed...1676#toc
bezza67
3.5 / 5 (8) Sep 14, 2008
You missed the point. If the atmospheric CO2 levels were as high as 1800ppm

1) Why did the planetary temperature not rise to lethal levels for all life on the Earth?
2) If there is a critical point at which irreversible global warming takes place, how come we are not still that hot?


1) No one claims that rising CO2 levels will kill all life on earth, or that it has in the past (obviously). This point represents a fundamental misunderstanding of the concerns with AGW.

2) No one claims that runaway heating will occur.

The concerns are that the rate of warming will may have devastating impacts over the next 100 years on the ecology, not that it will wipe it out.

When rapid climate change has happened in the past, it has been accompanied by massive changes in the bioshpere. Were we still nomadic and little spread over the globe, we could follow the climate to wherever it sustained us. Now, state borders have sprung up, agriculture in narrow and fragile bands feed millions, and glaciers that provide downstream drinking water to millions of people are vanishing.

Humanity will not die out from global warming, but millions may be displaced and threatened from rising seas, failed crop seasons and drought. We already husband the environment to sustain our species. It is prudent to activate this husbandry on a large scale and work to mitigate - and adapt - to changes that may impact severely and deleteriously on many populations.
Rute
4 / 5 (4) Sep 15, 2008
Ice cores have problems when using them as a proxy for temperatures. The gas levels in a Andean ice core can not be compared directly to the gas levels of an Antarctic or Greenland ice core. For some reason the processes that work in one way in the Antarctic work the reverse in the Andes.
http://www.nap.ed...1676#toc

Is there some information in the site you linked that would support your comment? If so, would you copy and paste short sections of this information to save us some time searching for it?
Bob_Kob
2.3 / 5 (6) Sep 15, 2008
Fuck were stupid arent we. Generations away will laugh in our faces because of the whole 'global warming fiasco'.
rubberman
1 / 5 (1) Sep 15, 2008
Go back to tuscani maestro....
GrayMouser
3 / 5 (2) Sep 15, 2008
Ice cores have problems when using them as a proxy for temperatures. The gas levels in a Andean ice core can not be compared directly to the gas levels of an Antarctic or Greenland ice core. For some reason the processes that work in one way in the Antarctic work the reverse in the Andes.
http://www.nap.ed...1676#toc

Is there some information in the site you linked that would support your comment? If so, would you copy and paste short sections of this information to save us some time searching for it?


Well, to start (pg 8):"The interpretation of oxygen isotope measurements in tropical ice cores is more complicated than for polar regions because it depends not only on temperature but also on precipitation in the adjacent lowlands."

Page 65 has 3 bullets that are interesting but page 66 has the following: "consequently, ice isotopic ratio measurements must be calibrated against independent temperature information in order to be used as a quantitatively accurate thermometer (Cuffey et al. 1995). Such calibrations have been applied for long-timescale records from the polar ice sheets, but not for low-latitude high-altitude ice cores (from the Andes, Kilimanjaro, and Tibet), where it is more difficult to isolate and quantify the temperature component of the signal."

There is more on page 66 about other influences. The interesting thing about the ice cores from the Himalayas is that none of them show a layer reflecting nuclear testing (http://www.livesc...s.html.)

All in all, ice cores provide a general idea of the local climate but deriving global climate from them is tricky.
Mesafina
1 / 5 (2) Oct 07, 2008
For all your arguing you all are missing the simple points:

1 - We do not know if humans are causing the climate to change. There is some data that suggests it might, but nothing is conclusive due to a general lack of information. Anyone who says that we do know, no matter if you think humans cause it or don't, is just making assumptions without data to support it. That is not scientific at all.

2 - Given that we don't know if we are causing it, but we do know that the impact on our society could be painful over time... there is no reason NOT to try to mitigate the potential effects just in case. It's like wearing your seatbelt. You don't know you are going to crash... you probably won't. But it is not a huge sacrifice of time to put it on compared to what you could lose by not. So it would be foolish to not buckle up.

It's that simple folks. We should do what we can just in case, because if we're wrong it will cost us much more down the road. If you are so sure that we AREN'T causing climate change... then go back to your church and leave your blind faith out of the comment section of a website about SCIENCE.

Thank you.