Sqrl said:
@the bolded red comment, Is that a typo on your part? The red line rises on the right side of the blue line and appears to fall on the right side as well (this is clearly seen if you look at the peaks and troughs of each line relation to one another). Second, to my knowledge both sides of the climate debate agree that there is an 800 year lag between when temperatures begin to rise and when C02 outgassing occurs as a result. Warmists believe that C02 acts in the natural system as purely a feedback mechanism but that in the case of AGW is becoming an initiator of that warming. This has been my experience reading warmist opinions like that of Gavin Schmidt of realclimate, but it is possible I assumed too broadly. For now I'll add that until recently I thought the claim about C02 as a natural feedback for glacial to interglacial temperature transitions seemed logical and reasonable, but a recent mathematic assessment of C02 in Nature asserts that it has second-order stationarity, and that has me questioning the natural feedback concept. The paper is a recent one though so there hasn't been a lot of reaction to it yet that I've seen, for now it's a bit of a question mark both ways to me, but from my (relatively) limited mathematical skills the paper appears to be solid. |
No it wasn't a typo but probably a mistake on my part. It was based off a couple off papers which I read a few years ago claiming that CO2 preceeded temperature by several hundred years (although their error margins were much higher than this). In fairness I was referring to the changes observed during the transition from glacials to interglacials which have generally been reported to be 'simultaneous' as opposed to the longer interglacial to glacial periods were CO2 cleary lags. I appreciate I didn't make that clear and to be honest I think you are right anyway, the new consensus does seem to be that there is a lag between the temperature rising and the CO2 following suite even regrading the glacial-interglacial periods.
Although as I mentioned in the second paragraph of the post, CO2 lagging behind temperature isn't surprising (and as you say in now generally accepted by both sides, obviously I was slighlty out of the loop on that!). This is where I just can't make up my mind on what goes on. So we have CO2 outgassing lagging ~800 years, probably caused by ocean warming likely started by weak orbital forcing. As far as I'm aware (please correct me if I'm wrong) the view now is that the orbital forcing should be too weak to account for the full extent of the temperature variation seen. That is why it has been suggested that the CO2 acts as a feedback. The CO2 itself though is only thought to be directly responsible for around 1 degree of further warming (source at bottom) and so it is generally thought that further feedbacks are triggered by this warming which account for the further temperature increase seen (e.g melting ice, water vapour, ocean circulation).
This is where the issue currently lies with me. If CO2 did act as a feedback mechanism and in doing so created further positive feedbacks then the drastic increase in current CO2 levels could be a potential problem. That said, the feedbacks cleary didn't run out of control in generating a run-away greenhouse effect which would suggest there is a control on CO2 (i.e. it only ever follows temperature). Furthermore, during the interglacial-glacial transitions CO2 again lags temperature which is the opposite effect you would expect to see if CO2 was acting as a feedback.
The best conclusion I can draw is that CO2 is purely a consequence of temperature and that other feedback mechanims (ice sheet waning ect) are wholey responsible for amplifying the weak initial increase in temperature caused by orbital forcing.
Do you have a link to that Nature paper you mention? I would be interested in reading it.
source
Jouzel et al, 1989. Global change over the last climatic cycle from the vostok
ice core record (Antarctica), Quaternary International, Vol. 2, pp. 15-24, 1989.
