Carbon dioxide not to blame in ice age mystery

Science News ^ | June 18th, 2009 | Sid Perkins

[SunkenCiv]

:’)

[cogitator]

What the author does do is undermine carbon dioxide as a driving force causing climate change. This data supports the idea that carbon dioxide is a lagging indicator of prior climate change.

That's a ridiculous statement. Even reading the abstract indicates it's only about the factor which caused a change in the timing of glacial/interglacial periods. For that particular aspect of paleoclimate, CO2 is now shown not to be the causative factor. This paper has nothing else to do with CO2 as a climate change driver, which primarily means a determinant of global temperature and changes in global temperature. You'll note that they even say in the abstract: "These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate,"

How does that statement "undermine carbon dioxide as a driving factor causing climate change"?

Congratulations on provoking me to comment!

Didja read the last paragraph of the Science News summary:

"In extending the record of carbon dioxide measurements, the study also shows that today’s levels — now above 380 parts per million and rising higher each year — are unprecedented during the past 2 million years."

How comforting is that?

Back to hibernation.

[neverdem]

That's a ridiculous statement. Even reading the abstract indicates it's only about the factor which caused a change in the timing of glacial/interglacial periods. For that particular aspect of paleoclimate, CO2 is now shown not to be the causative factor. This paper has nothing else to do with CO2 as a climate change driver, which primarily means a determinant of global temperature and changes in global temperature. You'll note that they even say in the abstract: "These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate,"

How does that statement "undermine carbon dioxide as a driving factor causing climate change"?

Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition

The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (PCO2), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pCO2) was relatively stable before the mid-Pleistocene climate transition. Glacial PCO2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PCO2 was similar to that of late Pleistocene interglacial cycles (<450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial PCO2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.

It's right there in the abstract.

Ice cores from Antarctica show that at the end of recent ice ages, the concentration of carbon dioxide in the atmosphere usually started to rise only after temperatures had begun to climb. There is uncertainty about the timings, partly because the air trapped in the cores is younger than the ice, but it appears the lags might sometimes have been 800 years or more.

If carbon dioxide positively forced towards warmer temperature we wouldn't need to worry about ice ages again. It's been much greater that 10 times the current concentration of CO2.

[cogitator]

does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.

It's about the cause of the climate transition (altered glacial/interglacial timing). It's not about the effect of CO2 on global temperatures.

If carbon dioxide positively forced towards warmer temperature we wouldn't need to worry about ice ages again.

We sure don't. Read my profile, point #5.

or this

The Start and End of our Interglacial (PDF of a slide presentation)

[Steve Van Doorn]

Thank you for answering the question.

It is your belief that CO2 and CH4 are the drivers of glaciation.

That is the answer I expected.

[Steve Van Doorn]

I am reading your other post which you seem to be disagreeing with the article you pointed me to.

Forget all that you tell me in your opinion what is the driver for glaciation?

[MHGinTN]

Gas passed by ruminants when the Sun hits a maunder minimum.

[cogitator]

Hey Steve:

Forget all that you tell me in your opinion what is the driver for glaciation?

Have I ever in the past referred you to my profile, point #5?

First of all, I won't be able to continue this, and for that I apologize. I made the recent mistake of replying to a post here on global warming. The temptation of trying to correct the repeated misstatements and misunderstandings I read here over and over again is very strong, and I have to remember and remind myself that all of my efforts were, and are going to be, essentially futile. So I will shut myself up, aided by the fact that happily I won't be able to touch a computer for two weeks*, and I am really, really slow at typing text on a standard phone keyboard (no, I don't have an Iphone).

*(wish I was going to Iceland, but I'm actually only going back to Wisconsin)

So the short (I'll do my best) answer to your question is that the "driver" of continental glaciation, i.e., the main thing that causes glacial periods, is low atmospheric CO2 concentrations. The reverse of that is, the main thing that causes interglacial periods is high (speaking Pleistocenically) CO2 concentrations. The difference of about 100 ppm CO2 between glacials and interglacials is the primary factor affecting the radiative balance that can accomplish the approximate 5 degree difference of global temperatures between glacials and interglacials. Note that the entire change is a combination of radiative forcing and feedback, with water vapor concentration (relative humidity) being the main feedback.

(hi palmer)

Nothing else in the Earth system can do this. Repeat, nothing else. Which means anything which could have plausibly influenced the Earth's climate over the entire Pleistocene. The only thing that can accomplish the necessary temperature change is radiative forcing due to atmospheric CO2.

But if you'll note in point #5 in my profile, the triggering factor is maximum and minimum insolation, caused by Milankovitch solar forcing. The insolation maxima and minima induce the necessary change direction in the climate state. CO2 atmospheric concentrations start to rise or fall in response to this trigger (depending on the direction of change) and over the ensuing millenia, bring the process to completion. Until the next trigger to reverse the process.

This is not my little opinion or theory. What I just summarized is scientifically accurate (though quite cursory), based on numerous investigations, a broad range of data, and all manner of interpretation and analysis.

So that's why when I see the ridiculous statement that atmospheric CO2 isn't a climate factor, I cringe. It's just wrong. Beyond the Pleistocene, there are events in deeper (i.e. older) paleoclimate that demonstrate without doubt how radiative forcing by atmospheric gases (notably CO2, but with help from methane and SO2) affects climate and global temperature. (As an aside, why do people accept with little question that SO2 aerosols from volcanic eruptions cool climate, but have a problem with increasing CO2 concentrations warming climate? Is it because one is just simpler to understand than the other and easier to observe on shorter-term time-scales?)

So there you go. That's my answer.

One more aside. I've recently been pondering why the Maunder Minimum (low sunspot numbers indicating lower solar activity, causing the Little Ice Age, probably) actually caused lower global temperatures, because the actual change in solar activity was small. I surmised that this was due to the small change causing larger climate feedbacks. Turns out that was basically right; other people have thought about this and done research and wrote papers about this.

The climate during the Maunder Minimum: a simulation with the Freie Universität Berlin Climate Middle Atmosphere Model (FUB-CMAM)

The Relative Importance of Solar and Anthropogenic Forcing of Climate Change between the Maunder Minimum and the Present

I won't have time to read these before I'm gone, so this will help me find them when I get back.

I hope what I wrote was useful. I always hope that.

[Steve Van Doorn]

I don’t agree with your conclusions even if based strictly from the articles From point # 5 but that is fine.

Thank you very much for your answers.

[PapaBear3625]

The articles you posted are a good start toward understanding the influence of the Sun's magnetic field on Earth's climate. In a nutshell,

1) sunspots are an indicator of the strength of the Sun's magnetic field.

2) The Sun's magnetic field helps deflect interstellar cosmic rays from hitting earth.

3) Cosmic rays (high speed ions) promote condensation of water vapor and create more of a cloud layer.

4) Clouds reflect sunlight, and thus can result in a cooler earth

[palmer]

with water vapor concentration (relative humidity) being the main feedback.

(hi palmer)

Hi Cog,
The water vapor feedback is more truism than truth. The energy transfers in weather (evaporation, condensation, and convection mainly) are 1000 times greater than the warming from all CO2, manmade or otherwise. Weather rules climate and not modeling weather properly, as I have pointed out time and time again, will result in inaccurate estimates of water vapor distribution.

We already know, for example, that the measured water vapor in the upper troposphere is lower than what the models predict. One's case for global warming quickly dries up if one assumes relative humidity only increases, ignoring the distribution of water vapor (which is weather).