Severinghaus told Crikey that he doesn’t make a habit of Googling his own research, but Bolt appeared on his radar when a librarian in Brisbane wrote to him asking if “I’d really meant what Bolt said I meant”.
He didn’t. “Many, many other studies have found that carbon dioxide causes the earth to warm. This is not controversial, and to continue to deny it is akin to denying that cigarette smoking causes cancer,” Severinghaus told Crikey. “The evidence for a human-caused warming of the globe is overwhelming. The scientific debate is over, and what we are seeing now is an attempt to mislead the public.”
Severinghaus explained how Bolt had been slippery with the facts, “…Bolt omitted the key piece of information that the warmings took 5,000 years, thus misleading the reader into thinking that carbon dioxide was not warming at the same time as temperature and thus cannot have caused the warming…”
Severinghaus wrote a letter to the editor of the Sunday Mail, but it was never published. He posted a comment on Bolt’s blog but told Crikey “…effectively I have not been able to make much if any response”.
“At the very least I would like it to go on record that Bolt’s abuse of my science is not done with my approval,” says Severinghaus.
So is the professor sick of having his research misrepresented in the press? “My research actually mostly isn’t misrepresented,” he told Crikey. “But it is sometimes misrepresented on climate-denialist websites. I suspect, though do not know, that Bolt got the info from a climate-denialists website.”
Bolt responded on his blog:
Severinghaus’s research shows CO2 levels have tended to rise AFTER the globe’s temperature starts to rise – and some 5000 years afterwards at that, which is what I drew attention to. This clearly suggests, as he and others have acknowledged, that the warming at least initially may not be caused by increased CO2, but in fact cause it. Severinghaus claims there is a later feedback mechanism so that the increased CO2 in turn increases the warming (many hundreds of years later), but this does not at all dispute the point I made – especially since the warming we’ve seen has occured for less than 150 years. So what caused that initial warming in those previous warming episodes, and in this? Yes, he’s still a man-made global warming believer, and is upset that I draw attention to this curious fact he’s helped to discover, but bad luck to him. His rage and spluttering should not be allowed to obscure the central fact – that Al Gore shows slides from previous ice age that contrary to what he suggests in fact show increased CO2 concentrations initially FOLLOWING rising temperatures (by perhaps as much as 5000 years, say some researchers) and not before.
Yes, CO2 isn’t the only thing that affects climate, but Bolt mislead his readers by making it appear that the warming preceded the increase in CO2 when only a small part of it did. Severinghaus explains:
Does this prove that CO2 doesn’t cause global warming? The answer is no.
The reason has to do with the fact that the warmings take about 5000 years to be complete. The lag is only 800 years. All that the lag shows is that CO2 did not cause the first 800 years of warming, out of the 5000 year trend. The other 4200 years of warming could in fact have been caused by CO2, as far as we can tell from this ice core data. …
In other words, CO2 does not initiate the warmings, but acts as an amplifier once they are underway. From model estimates, CO2 (along with other greenhouse gases CH4 and N2O) causes about half of the full glacial-to-interglacial warming.
And Bolt’s blog post is also extremely misleading, pointing to a New Scientist story that states:
Now some astronomers are predicting that the sun is about to enter another quiet period. With climate scientists warning that global warming is approaching a tipping point, beyond which rapid and possibly irreversible damage to our environment will be unavoidable, a calm sun and a resultant cold snap might be exactly what we need to give us breathing space to agree and enact pollution controls.
Bolt’s take on this? They’ve moved on from being scared about global warming to being scared about global cooling.