Greenhouse Gas Effect Consistent Over 420 Million Years

Terra Daily ^ | 03/29/2007 | Staff Writers

[cogitator]

New calculations show that sensitivity of Earth's climate to changes in the greenhouse gas carbon dioxide (CO2) has been consistent for the last 420 million years, according to an article in Nature by geologists at Yale and Wesleyan Universities.

A popular predictor of future climate sensitivity is the change in global temperature produced by each doubling of CO2 in the atmosphere. This study confirms that in the Earth's past 420 million years, each doubling of atmospheric CO2 translates to an average global temperature increase of about 3 Celsius, or 5 Fahrenheit.

According to the authors, since there has continuously been life on the planet over this time span, there must be an ongoing balance between CO2 entering and leaving the atmosphere from the rocks and waters at Earth's surface. Their simulations examined a wide span of possible relationships between atmospheric CO2 and temperature and the likelihood they could have occurred based on proxy data from geological samples.

Most estimates of climate sensitivity have been based on computer simulations of climate or records of climate change over the past few decades to thousands of years, when carbon dioxide concentrations and global temperatures were similar to or lower than today. Such estimates could underestimate the magnitude of large climate-change events.

To keep Earth's carbon cycle in balance, atmospheric CO2 has varied over geologic time. Carbon-cycle models balance chemical reactions that involve carbon, such as photosynthesis and the formation of limestone, on a global scale. To better predict future trends in global warming, these researchers compared estimates from long-term modeling of Earth's carbon cycle with the recent proxy measurements of CO2.

This study used 500 data points in the geological records as "proxy data" and evaluated them in the context of the CO2 cycling models of co-author Robert Berner, professor emeritus of geology and geophysics at Yale who pioneered models of the balance of CO2 in the Earth and Earth's atmosphere.

"Proxy data are indirect measurements of CO2 - they are a measure of the effects of CO2," explained co-author Jeffrey Park, professor of geology and geophysics at Yale who created the computer simulations for the project. "While we cannot actually measure the CO2 that was in the atmosphere millions of years ago, we can measure the geologic record of its presence. For example, measurement of carbon isotopes in ancient ocean-plankton material reflects atmospheric CO2 concentrations."

Led by Dana L. Royer, assistant professor of Earth and Environmental Sciences at Wesleyan University, who did his graduate work in geology at Yale, the collaboration simulated 10,000 variations in the carbon-cycle processes such as the sensitivity of plant growth to extra CO2 in the atmosphere. They evaluated these variations for a range of atmospheric warming conditions, using the agreement with the geologic data to determine the most likely warming scenarios. The model-estimated atmospheric CO2 variations were tested against data from ancient rocks.

Other proxy measurements of soil, rock and fossils provided estimates of CO2 over the past 420 million years. Calculation of the climate sensitivity in this way did not require independent estimates of temperature. It incorporated information from times when the Earth was substantially warmer and colder than today, and reflects the sensitivity of the carbon-cycle balance over millions of years.

"Our results are consistent with estimates from shorter-term records, and indicate that climate sensitivity was almost certainly greater than 1.5, but less than 5.5 degrees Celsius over this period," said Park. "At those extremes of CO2 sensitivity, [1.5C or 5.5C] the carbon-cycle would have been in a 'perfect storm' condition."

[cogitator]

If my warped memory serves me correctly, 3 deg C for every doubling of CO2 content implies a logarithmic function.

You're right, it does.

Of course, I doubt that the rate of CO2 increase is constant; with our sorry luck, it's probably accelerating.

Actually, I think it's closer to a linear increase right now.

[ancient_geezer]

New calculations show that sensitivity of Earth's climate to changes in the greenhouse gas carbon dioxide (CO2) has been consistent for the last 420 million years, according to an article in Nature by geologists at Yale and Wesleyan Universities.

***

This study used 500 data points in the geological records as "proxy data" and evaluated them in the context of the CO2 cycling models of co-author Robert Berner, professor emeritus of geology and geophysics at Yale who pioneered models of the balance of CO2 in the Earth and Earth's atmosphere.

"Proxy data are indirect measurements of CO2 - they are a measure of the effects of CO2," explained co-author Jeffrey Park, professor of geology and geophysics at Yale who created the computer simulations for the project. "While we cannot actually measure the CO2 that was in the atmosphere millions of years ago, we can measure the geologic record of its presence. For example, measurement of carbon isotopes in ancient ocean-plankton material reflects atmospheric CO2 concentrations."

Hmmm, wonder which 500 points in 450 million years they chose to use:

 

Global Surface Temperature and Atmospheric CO2 over Geologic Time 

Late Carboniferous to Early Permian time (315 mya -- 270 mya) is the only time period in the last 600 million years when both atmospheric CO2 and temperatures were as low as they are today (Quaternary Period ).

Temperature after C.R. Scotese
CO2 after R.A. Berner, 1994

•     There has historically been much more CO2 in our atmosphere than exists today. For example, during the Jurassic Period (200 mya), average CO2 concentrations were about 900 ppm or about 2.5 times higher than today. The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Ordovician Period, exceeding 6000 ppm -- more than 16 times higher than today.

•     The Carboniferous Period and the Ordovician Period were the only geological periods during the Paleozoic Era when global temperatures were as low as they are today.
  
  To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age, with CO2 concentrations nearly 15 times higher than today-- 5500 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.

[JustDoItAlways]

Berner's latest CO2 estimates are shown in this graph. Berner's are the yellow orange line - The GeoCarb III line.

So if any of you can figure out how these scientists took the yellow orange line and decided historical temperatures match up with it pretty close, I'll give you a million bucks

Berner's CO2 estimate is 2000 ppm 140 million years ago (versus today of 384 ppm). Was temperature 5 times higher 140 million years ago? NO. Was it slightly warmer (and quite comfortable for a naked ape)? YES. Does it match up with global warming theory which says we should get a 3.5C warming for every doubling of C02? NO.

Berner's estimate of CO2 500 million years ago is 6,000 ppm. The earth would have been fried if global warming theory was correct.

[bricks4all2]

Perhaps Berner would prefer you reference his actual article in Nature rather than the staff writers' "Cliff's Note's" proxy.

[ancient_geezer]

Looking at change in CO2 in relation to average global temperature from the graphic in #22, one wonders what definition of the term "consistant with" takes in the Berner dictionary.

[ancient_geezer]

The abstract for the Nature article.

 

Climate sensitivity constrained by CO2 concentrations over the past 420 million years

Climate sensitivity constrained by CO2 concentrations over the past 420?million years

Nature 446, 530 (2007). doi:10.1038/nature05699

Authors: Dana L. Royer, Robert A. Berner & Jeffrey Park

A firm understanding of the relationship between atmospheric carbon dioxide concentration and temperature is critical for interpreting past climate change and for predicting future climate change¹. A recent synthesis² suggests that the increase in global-mean surface temperature in response to a doubling of the atmospheric carbon dioxide concentration, termed 'climate sensitivity', is between 1.5 and 6.2 °C (5–95 per cent likelihood range), but some evidence is inconsistent with this range^{1, 2, 3, 4, 5}. Moreover, most estimates of climate sensitivity are based on records of climate change over the past few decades to thousands of years, when carbon dioxide concentrations and global temperatures were similar to or lower than today^{1, 6}, so such calculations tend to underestimate the magnitude of large climate-change events⁷ and may not be applicable to climate change under warmer conditions in the future. Here we estimate long-term equilibrium climate sensitivity by modelling carbon dioxide concentrations over the past 420 million years and comparing our calculations with a proxy record. Our estimates are broadly consistent with estimates based on short-term climate records, and indicate that a weak radiative forcing by carbon dioxide is highly unlikely on multi-million-year timescales. We conclude that a climate sensitivity greater than 1.5 °C has probably been a robust feature of the Earth's climate system over the past 420 million years, regardless of temporal scaling.

 

Looking at the Yale news release for the article [ http://www.yale.edu/opa/newsr/07-03-28-02.all.html ], we find an interesting statement in regards the lack of validation for temperature in the paleo record they used in respect to their simulations of CO2, to come to their conclusions:

"Led by Dana L. Royer, assistant professor of Earth and Environmental Sciences at Wesleyan University, who did his graduate work in geology at Yale, the collaboration simulated 10,000 variations in the carbon-cycle processes such as the sensitivity of plant growth to extra CO₂ in the atmosphere. They evaluated these variations for a range of atmospheric warming conditions, using the agreement with the geologic data to determine the most likely warming scenarios. The model-estimated atmospheric CO₂ variations were tested against data from ancient rocks.

Other proxy measurements of soil, rock and fossils provided estimates of CO₂ over the past 420 million years. Calculation of the climate sensitivity in this way did not require independent estimates of temperature. It incorporated information from times when the Earth was substantially warmer and colder than today, and reflects the sensitivity of the carbon-cycle balance over millions of years."

 

Seems they only took empirical measures of CO₂ proxies with respect to geological age to compare against their simulations of what CO2 ought to be according to their implicit assumptions of with no validation of actual magnitude of temperature variation from the geological record.

As can be observed from the results represented in #22 above, raw climate sensitivity based on temperature ranges throughout the paleo-record do not correlate well at all with CO2 variation.

Per the statement from the abstact "but some evidence is inconsistent with this range^{1, 2, 3, 4, 5}." "some evidence is inconsistent" could easily be seen as a prime candidate for understatement of the decade.

[xcamel]

FReepmail me to get on or off

Click on POGW graphic for full GW rundown

Ping me if you find one I've missed.

---

[bricks4all2]

Take a look and answer one simple question.

http://www.nature.com/nature/journal/v446/n7135/extref/nature05699-s1.pdf

Would you send your kids to either Wesleyan or Yale?

[JustDoItAlways]

This link (below) shows the best estimates of temperature over the past 540 million years (chart is too big to paste.)

420 million years ago was about 4C warmer than today. (I believe this is based on Berner's own estimate from GeoCarb).

His CO2 estimates would represent 4 doublings of CO2 so they are clearly saying the senstivity to CO2 is on the very low end of the estimate - probably under 1.5C (rather than between 1.5C to 6.5C) for a doubling of CO2.

http://en.wikipedia.org/wiki/Image:All_palaeotemps.png

It is certainly NOT 3C for every doubling (which would make the temperature 420 million years 12C higher than today and certainly not 6.5C for every doubling which would put the temperature 26C higher than today.) Once again, 4C is what Berner's own estimates say or about 1C for every doubling.

He probably needed to downplay the result (while still publishing his research) so he could still get invited to all the great global warming parties (if you know what I mean).

[cogitator]

Perhaps Berner would prefer you reference his actual article in Nature rather than the staff writers' "Cliff's Note's" proxy.

You need a subscription to read articles in Nature. That's why I don't do that.

[cogitator]

Was temperature 5 times higher 140 million years ago? NO. Was it slightly warmer (and quite comfortable for a naked ape)?

140 million years ago was the end of the Jurassic. Last I checked, there weren't even ice caps then. Last I checked, there weren't any naked apes running around comfortably then, either. Did you lose a couple powers of 10 in the timeline, somewhere?

Berner's estimate of CO2 500 million years ago is 6,000 ppm. The earth would have been fried if global warming theory was correct.

Though I try to keep up on things, I don't know what the "Royer compilation" is. The graph shows a Silurian or Ordovician measurement of about 5500 ppm CO2. So are you implying the 6000 ppm was wrong or that the temperature extrapolated from the CO2 sensitivity figure wouldn't work for the Cambrian? (More on that below in other replies.)

[aruanan]

This study confirms that in the Earth's past 420 million years, each doubling of atmospheric CO2 translates to an average global temperature increase of about 3 Celsius, or 5 Fahrenheit.

Or that increases of 3C in the global temperature are followed by doubling of atmospheric CO2.

Related to this is an earlier paper by Rothman (Rothman, D.H.  2002.  Atmospheric carbon dioxide levels for the last 500 million years.  Proceedings of the National Academy of Sciences USA 99: 4167-4171.). From a review of the paper:

Rothman reports that the CO2 history he derived "exhibits no systematic correspondence with the geologic record of climatic variations at tectonic time scales."  In another place he writes that "comparison with the geologic record of climatic variations reveals no obvious correspondence."  And in yet another place he says that although the most recent cool period corresponds to the relatively low CO2 levels of the present, "no correspondence between atmospheric CO2 concentration and climate is evident in the remainder of the record."

If the truth be told, however, a simple visual examination of the author's plot of CO2 and climate vs. time clearly indicates that the three most striking peaks in the atmospheric CO2 record occur either totally or partially within periods of time when earth's climate was relatively cool.  Hence, not only is there no proof for the climate-alarmist contention that higher CO2 concentrations tend to warm the planet, there is evidence in this study to suggest that just the opposite may be true.

Related to the connection between atmospheric temperature and CO2:

Reference
Fischer, H., Wahlen, M., Smith, J., Mastroianni, D. and Deck B.  1999.  Ice core records of atmospheric CO2 around the last three glacial terminations.  Science 283: 1712-1714.

What was done
The authors examined contemporaneous records of atmospheric CO2 concentration and temperature derived from Antarctic ice cores that extended back in time through the last three glacial-interglacial transitions.

What was learned
In all three of the most recent glacial terminations, the earth warmed well before there was any increase in the air's CO2 content.  In the words of the authors, "the time lag of the rise in CO2 concentrations with respect to temperature change is on the order of 400 to 1000 years during all three glacial-interglacial transitions."  During the penultimate (next to last) warm period, there is also a 15,000-year time interval where distinct cooling does not elicit any change in atmospheric CO2; and when the air's CO2 content gradually drops over the next 20,000 years, air temperatures either rise or remain fairly constant.

What it means
One of the reasons for conducting studies of this type is to see what can be learned about the ability of increases in atmospheric CO2 to enhance earth's natural greenhouse effect and induce global warming.  As is readily evident from the work described here, however, the relationship between temperature and CO2 appears to be just the reverse of what is assumed in all of the climate model studies that warn of dramatic warming in response to the ongoing rise in the air's CO2 content: temperature rises first, and then comes an increase in atmospheric CO2.  Or, CO2 remains essentially unchanged while temperatures drop.  Or, CO2 drops while air temperature remains unchanged or actually rises.  Nothing even comes close to resembling what we are continually being warned about by state-of-the-art global climate models.

So what is one to believe?  Theoretical predictions or historical fact?  The choice of wisdom would appear to us to be history.  It has an uncanny way of repeating itself.

[RockinRight]

I found a calculator for what it would take to warm the planet Mars with a certain amount of CO2.

What I found was it took an insane increase in CO2 (about six times the increase that we've seen on Earth) to warm Mars up 5 degrees.

[cogitator]

Here's the small version of that very nice plot.

His CO2 estimates would represent 4 doublings of CO2 so they are clearly saying the senstivity to CO2 is on the very low end of the estimate - probably under 1.5C (rather than between 1.5C to 6.5C) for a doubling of CO2.

The article says that sensitivity is between 1.5 and 5.5 C. The Cambrian in this figure gets to 7.5 - 7.8 C higher than present, in the 4 doubling range. If the sensitivity is 2 C, that's 8 degrees C higher.

Now, the article says the "average" sensitivity was 3 C - maybe there's a period when the sensitivity is considerably higher. As the continents move around, climate is substantially affected -- the proposed explanation, from Crowley and Berner, of the brief (as can be nicely seen in ancient_geezer's plot) Ordovician glaciation is that Gondwanaland wandered directly over the South Pole.

He probably needed to downplay the result (while still publishing his research) so he could still get invited to all the great global warming parties (if you know what I mean).

Oh, I'm sure ol' Doc Berner still gets his invites. Especially those wine-and-cheese National Academy of Sciences parties.

Thanks for alerting me to that plot. It really demonstrates the Holocene stability "envelope" nicely, and everybody should remember that the much-maligned Hockey Stick doesn't show up until 1000 years BP.

[cogitator]

By the end of this week, I hope to finish my explanation of the lag non-issue in my profile.

The reviews of the papers are from a noted global-warming skeptical site, in case you were not aware of their provenance.

[RightWhale]

I think it is the situation on planet Venus where atmospheric pressure is 100X earth and much of that is CO2 that caused all this intellectual activity among the Algores and other New Agers. Runaway greenhouse effect they say and worry earth could become like that. That's what they told us in grammar school in the 50s when they also said we had world oil reserves for 20 years. I remember back then that many of my fellow fifth graders were already skeptical of much that we were told and sometimes wonder if they have become rank and file True Believers through dietary effects on their ossified brain lobes.

[JustDoItAlways]

The Cambrian in this figure gets to 7.5 - 7.8 C higher than present, in the 4 doubling range. If the sensitivity is 2 C, that's 8 degrees C higher.

Now you are changing the timeline. Cambrian's temperatures of 7.5C are 540 million years ago when CO2 was in the 7,000 ppm range (which is no longer in the 4 doublings range but in the 5 doublings range).

The paper was about the last 420 million years not 540 million years

And if you want to go back a little farther to, let's say, 600 million years ago, pre-Cambrian, this is the time of the great SnowBall Earth period when it is proposed that the entire Earth froze over, even the oceans at the equator.

Why would the entire Earth freeze over. Simple, all of the continents were locked together at the time, over the south pole. Again, other things, other than CO2 are the main driver of climate.

Your Cambrian example of 7,000 ppm is actually one of the actual dangers of too much CO2. At 7,000 ppm, humans would find it very difficult to breath. CO2 asphyxiation would become a significant problem for most mammals. Of course, we can never get to those levels since we would have run out of fossil fuels about 1,000 years short of ever reaching those numbers. In addition, O2 levels were higher back then which would have provided some compensation.

[bricks4all2]

“You need a subscription to read articles in Nature. That’s why I don’t do that.”

Then this post has limited credibility from the start. Well it is the internet, and such a low standard can be expected. I will probably get a copy to see if there is any interesting science in there.

[cogitator]

I will probably get a copy to see if there is any interesting science in there.

Subscriptions cost money. If I posted a link to a subscription-only article, people would complain that they can't read it. I used to subscribe to Science, but it was far more expensive than a monthly trip to the library and an occasional emergency run for a pertinent article.

[cogitator]

Now you are changing the timeline. Cambrian's temperatures of 7.5C are 540 million years ago when CO2 was in the 7,000 ppm range (which is no longer in the 4 doublings range but in the 5 doublings range).

Maybe. The peak is about 7,000, and there's got to be some pretty significant error bars on that. I'd have to read the actual paper (as suggested above; haven't had a chance yet) to get a better feeling for how they arrived at the average climate sensitivity value.

The paper was about the last 420 million years not 540 million years.

Excellent point, and there are actual measurements (Royer) back that far, according to the figure.

And if you want to go back a little farther to, let's say, 600 million years ago, pre-Cambrian, this is the time of the great SnowBall Earth period when it is proposed that the entire Earth froze over, even the oceans at the equator. ... Why would the entire Earth freeze over. Simple, all of the continents were locked together at the time, over the south pole. Again, other things, other than CO2 are the main driver of climate.

Also (I believe), significantly (30%?? could be way off, working from memory) lower solar output. It also seems to me that I saw something recently questioning the "depth" of the Snowball Earth cold. Don't quote me.

CO2 asphyxiation would become a significant problem for most mammals. Of course, we can never get to those levels since we would have run out of fossil fuels about 1,000 years short of ever reaching those numbers. In addition, O2 levels were higher back then which would have provided some compensation.

There weren't even any land animals in the Cambrian, were there?

Good thought-provoking questions here. Again, thanks for finding that plot.