A kind of vindication, and vague reason for optimism

Here's a slightly altered version of something I just posted at Catallaxy:

Over at Skeptical Science, Roger Pielke Snr (quite a favourite of climate change skeptics for many a year) been actively commenting in a recent post which criticised him for overstating the case on what’s been happening with ocean warming since 2004. (He says there is none; everyone else says there is no reason to be so confident based on the short timeframe and doubts about the adequacy of the measuring system).

Most interestingly, at two different points he says:

“Thus to conclude that I have ever not been concerned about the addition of CO2 and how it affects the climate system misrepresents my perspective. I am particularly concerned with respect to the biogeochemical effects of added CO2.” and

“In terms of CO2, we do not even need to discuss global warming to be concerned by uncontrolled increases in its atmospheric concentration. We see directly from observations of atmospheric concentrations of CO2 that humans are increasing its levels. If global warming were not occurring at all, we should still be concerned.”

Which is what I have been saying since, oh, 14 Nov 2006. (Although I have been persuaded since then that AGW itself is also a serious concern.)

I note that Pielke does not make it clear what biogeochemical effect he is talking about: the one I have concentrated on is ocean acidification, but I can't see that he has ever made reference to it at his blog. Is there another that he is referencing? He does talk about biogeochemical effects in relation to anthrogenic land cover change, but it doesn't sound as if this paper talks about CO2 causing biogeochemical effects.

So what his precise concerns are remains a bit of a mystery to me, but certainly I still believe that, like his son, he is being disingenuous by letting his warming skepticism (or in his son's case, glee over IPCC mistakes) be promoted all over the blogosphere and thus encourage policy inaction on CO2, when in fact he claims it's a "reason to be concerned."

Meanwhile, I see that a new study that did the exercise of looking at what would happen to CO2 levels and temperature if you never built another CO2 emitting device. The answer is a bit surprising:

The researchers found that atmospheric concentrations of CO₂ would stabilize at less than 430 parts per million (ppm) and the increase of global mean temperatures since preindustrial time would be less than 1.3°C (2.3°F).

"The answer surprised us," says Davis. "Going into this study, we thought that existing sources of CO2 emissions would be enough to push us beyond 450 ppm and 2°C warming." In light of common benchmarks of 450 ppm and 2°C, these results indicate that the devices whose emissions will cause the worst impacts have yet to be built.

Of course, it's impossible to turn off the new CO2 making device switch, but it does emphasise that aggressive action on CO2 production has a vague chance of working to limit temperature increases.