2011-10-28 13:37:26Question about CO2 lag and paleo data
John Cook

john@skepticalscience...
130.102.158.12

Got this email:

The 800-year lag continues to be a favored argument. I see it used literally every day, and its users seem convinced that it’s decisive. 

What you have on the site is good, as always, but it concentrates on explaining why CO2 lags the initial temp increase in Milankovitch-style events. This is pretty much always the information that gets used to counter the “CO2 lags temp” people. What I never see used is the argument that CO2 doesn’t ALWAYS lag 

For example: If I understand correctly, the cause of the temp increase at the Permian-Triassic boundary is believed by most to be the increase in GHGs resulting from massive vulcanism. If that’s the case, wouldn’t the GHGs and temps have increased more or less simultaneously, without any lag?

I can’t figure out why I never see anyone using this argument, which seems much easier to express than the feedback mechanism we have to use for Milankovitch cycles. “That’s not always true” is a more decisive argument than “Right, that’s true, but here’s the complicated explanation of why it doesn’t mean anything.”

There has to be evidence for this somewhere. It’s not possible that EVERY warming for which we have data exhibits the lag, is it?

2011-10-31 22:28:36
Ari Jokimäki

arijmaki@yahoo...
192.100.112.210

The problem is the large uncertainty bars in dating the samples for very old climate proxies. One cannot determine the lead/lag situation there. Long time ago I even made a blog post where I showed that in the Vostok ice core one can easily find many places where CO2 leads.