Does the global temperature lag CO2? More flaws in the Shakun et al. paper in Nature.
Over the past two weeks, perhaps a dozen people asked me about the recently published paper of Shakun et al. in Nature. It allegedly demonstrates that the global temperature followed CO2 around the warming associated with the last interglacial warming, between 20 to 10 thousand years ago. (Incidentally, if you don’t have a subscription to nature, take alook here). One guy even sent the story as a news item on NPR. So, having no other choice, I decided to actually read the paper and find what is it all about. Should I abandon all that I advocated over the past decade?
First some prologue. One of the annoying facts for alarmists is that ice cores with a sufficiently high resolution generally show that CO2variations lag temperature variations by typically several hundred years. Thus, the ice cores cannot be used to quantify how large is the effect thatCO2 has on the climate. In fact, there is no single time scale whatsoever over which CO2 variations can be shown to be the origin of temperature variations (not that such an effect shouldn’t be present, but because of its size, no fingerprint was actually found yet, even if you hear otherwise!). This fact stands as a nasty thorn in the alarmist story. So, it is no surprise that when Nature recently published that (finally) there is an observation showing that the temperature (and in particular, the average global temperature) lags CO2, that the alarmist community had a field day over it.