What do you think of this example of CO2 driving climate change?

Question

Anthropogenic global warming (AGW) doubters often say that they require an example of CO2 driving climate change before they'll believe AGW. A few days ago, a paper was published in 'Nature' describing just such an event entitled 'Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels'

"We find that Greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene."

http://www.nature.com/nature/journal/v454/n7208/abs/nature07223.html

As Gavin Schmidt puts it, "Lunt et al find that only the change in CO2 (400 ppm to 280 ppm) can explain the changes in the ice sheet. None of the other ideas come even close."

http://www.realclimate.org/index.php/archives/2008/08/friday-round-up/

What do you think of this example of CO2 driving climate change?

Answer 1

Looks like a good example to me.  The deniers argue that you have to throw out the other data, but that's ridiculous.  We know that increasing CO2 can both cause temperature rise and be caused by increasing temperature.  It's not an either/or scenario.

Of course, the deniers won't be convinced because they don't want to be.  They've shown this time and time again - they ask for some specific evidence, we provide it, and they pretend it never happened.

Answer 2

“Anthropogenic global warming (AGW) doubters often say that they require an example of CO2 driving climate change before they'll believe AGW”

I can’t speak for anyone else but I’m certain that the evidence I’ve always asked for is demonstration that Anthropogenic CO2 causes global warming, that why it’s called AGW. I don’t believe that I’ve ever asked for demonstration that “CO2 drives climate change”... however, I’ll still play.

You give us 2 links to the same document which you offer as a demonstration of “CO2 driving climate change”. Unfortunately this document is only available on a per pay basis, so I can only make comment on what’s available in the abstract, not the full text; however, I’ll give it a go.

The first thing I notice is that this paper is concerned with glaciations due to reduced CO2, not warming due to increased CO2. I’ve read many times in your posts that you recognise the evidence that in the past increased warming has preceded increased CO2 concentrations. You’ve insisted that the reason we have global warming now is only due to the quantities of Anthropogenic CO2 emitted in the post industrial era that is ‘forcing’ the climate in a way that did not occur in previous significant climate changes.

It is rather odd then that you choose this document to support your position. “We find that Greenland glaciation  is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene.” They conclude that reduced CO2 has preceded cooling, which is significantly at odds with what we understand from the more recent ice core samples.

It concerned me to read this too as I’m not currently convinced that CO2 is significant at all to climate change (to my mind it’s a result, not a cause). Then I saw that the paper is based on modelling,  not measurement... “our model results suggest”

Here are some contrary conclusions covering the same time period, based on measurements not models.

“At present, our results do not support the suggestion that Pliocene warming was caused by carbon dioxide increase since such changes are not consistent with the SST distributions derived from deep sea cores” http://www.giss.nasa.gov/research/featur...

“Oxygen isotope shifts that occur at Oi1 time, in the middle Miocene and in the mid-Pliocene overshoot CO2 and sea level estimates, suggesting an amplification within the climate system and implying that CO2 is not the sole cause of these climate changes. Published modeling results deemphasize the importance of ocean gateways and emphasize the importance of CO2 on cryospheric development.” http://adsabs.harvard.edu/abs/2006AGUFMP...

I think it’s still your case to prove.

Answer 3

Then you have to throw away 400 thousand years of climate data that indicate that temperature changes drive atmospheric CO2 levels and not the other way around. If anthropogenic CO2 levels have extended the current interglacial period, you should be thankful!

Answer 4

A so-so example at best. Why doesn't the alarmist faction ever admit to natural occurrences?

http://www.livescience.com/environment/0...

Answer 5

It is an interesting theory , and one I'm open to . However , nothing about it puts other theories to bed . It's not an example of climate change I'm looking for where Co2 is concerned . I would like to see examples where it has driven temperature . Here are some other Arctic theories .

http://www.sciencedirect.com/science?_ob...

http://www.sciencemag.org/cgi/content/ab...  

Answer 6

Dana I feel they are grasping at straws, since in order to know something beyond a shadow of a doubt you'd have to be there to experience what occurred.  

Answer 7

Frankly it is a convenient nonsensical theory.  Words mean things.  They said:

"By contrast, our model results suggest that climatic shifts associated with the tectonically driven closure of the Panama seaway with the termination of a permanent El Niño state or with tectonic uplift are not large enough to contribute significantly to the growth of the Greenland ice sheet; moreover, we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the Earth's orbit"  

It is not an "or", it is all of the above.  All these factors may have contributed to glaciation.  It should have been "and" or "and/or"

Still they don't attempt to explain why there is a lag in CO2 concentrations because if they attempt to explain that their theory falls apart.  Isn't it obvious that this is simply a conclusion  first, theory to follow.   Alarmists love to argue out of ignorance rather than facts.  They say "what else could have caused it?"  Not this or that or that as if this is somehow evidence for human caused warming.  It is more of the same, Nonsense.