Good news on global warming (maybe)

‘Good news’ is an odd thing to associate with ‘global warming’; it just sounds wrong. As implied though, my association is strictly tentative. In addition, even if true, it might prove to be a slight exaggeration. Hopefully the strength of my association solidifies with time.

I’m consistently frustrated and perplexed by persistent assertions from the denier camp that those of us who recognize the benefits of science apparently relish the idea of anthropogenic global warming. Not so, and no one should need to spell it out like that.

I’ll grant that the Greenpeace crowd seem to, but they’re an unsophisticated minority and many of us find them tedious. I think the Greenpeace claque are insane. I believe that most of their positions are catastrophically counterproductive, not just politically, but also environmentally.

(Libertarian) writers like Matt Ridley and Michael Shermer have indicated that while they accept the basic science of global warming, they don’t believe it will lead to the nightmare scenario that the – well, let’s just call them ‘leftists’ – have been making noises about. (Call Ridley and ilk ‘lukewarmists’, they hate that.) According to a recent article in New Scientist, some of these more sophisticated ‘sceptic’ cadres may not be totally disappointed. If so, I couldn’t be happier for them.

A study lead by Andreas Schmittner (of Oregon State University) has indicated that the global climate might be slightly less sensitive to atmospheric CO2 concentrations than what previous data bore out. The authors of the actual paper, published in the journal Science, have themselves described many of their study’s limitations. And, for the sake of the more stupid elements in the media, stressed that atmospheric CO2 levels still do contribute significantly to warming.

The paper described efforts to probe climate sensitivity to atmospheric CO2 concentrations using model calculations based on temperature reconstructions of the Last Glacial Maximum (LGM) ice age, which occurred around 20,000 years ago.

A major pitfall in this study was that it only used one climate model to calculate the data. For these findings to affect consensus, they would need to be replicated in several other models used by climatologists. The model used, UVic (of the Canadian Centre for Climate Modelling and Analysis, or CCCMA) has been criticized before by scientists for being overly simplistic. In 2010, Tamino found that CCCMA models were failing to reproduce 20th century temperatures. I also noted that the paper didn’t cover the more complicated ancillary factors like ocean acidification.

Another shortcoming of the study that struck me (elucidated in Skeptical Science’s very detailed commentary) was that the mean temperatures assigned to the LGM for the purpose of the study was significantly higher than most paleoclimate estimates.

According to the study, the average global temperature during the LGM was only 2.6 Kelvin cooler than the current global temperature. Mainstream estimates of mean LGM temperature, based on temperature reconstruction data indicate that the period was roughly 4-7K cooler than the current global temperature. Notably, climatologist Gavin Schmidt told New Scientist:

A different model would give a cooler Last Glacial Maximum, and thus a larger sensitivity.

According to Skeptical Science: if this study holds up, it not only constrains the more terrifying predictions of other models, it also constrains many of the deniers’ staple hypotheses such as low climate CO2 sensitivity and negligible warming. New Scientist quotes Schmittner:

Very small changes in temperature cause huge changes in certain regions, so even if we get a smaller temperature rise than we expected, the knock-on effects would still be severe.

If you are interested in the finer points of the paper, check out the commentary on Skeptical Science, linked above. Much of what I’m discussing here is covered in much greater detail there.

In the paper, the authors described a number of their own caveats, then added:

Until the above questions are resolved, it’s premature to conclude that we have disproven high climate sensitivities, just because our statistical analysis assigns them low probabilities.

As usual, different news sources have framed the findings in different ways. A Google News search for “Andreas Schmittner” yielded the following:

  • CO2 sensitivity possibly less than most extreme projections (Los Angeles Times)
  • Global warming much less serious than thought – new science (Register – the URL contains the similarly optimistic character string ‘runaway_warming_unlikely’)
  • Carbon dioxide doubling impact has limit (USA Today)
  • New global warming estimate (Sydney Morning Herald)

The last one is my favourite. After yesterday’s sojourn with bullshit, I’ll try to keep the meta-journalism to a minimum.

My least favourite article dealing with these findings was posted on Anthony Watts’ popular internet AGW denier den Watts Up With That? The post is entitled “New study in Science shows climate sensitivity overestimated”. To wit:

Their estimate is 2.4C for a doubling of CO2 (sic), which is still higher than Spencer and others have estimated but significantly lower than IPCC’s projections.

Skeptical Science keep a modest catalogue of rebuttals specific to Watts and a more meaty one for his pal Roy Spencer. It always amuses me to read prolific deniers cherry-picking from a vast and exponentially accruing pile of scientific papers on climate change and justifying their selections with diminutive preambles. Once again, consider the bottom of the barrel clean.

Most scientists believe that a temperature rise of more than 2K is too dangerous to allow, because it risks runaway feedback-activated global warming. This experiment predicts that if carbon-intensive power generation and infrastructure continues to emit unchecked, we can still expect more than 2K warming.

As Schmittner himself told Science Daily:

Hence, drastic changes over land can be expected. However, our study implies that we still have time to prevent that from happening, if we make a concerted effort to change course soon.

So it could fairly be said I exaggerated when I said that this study potentially brings good news. Maybe we’re merely dealing with potentially less-bad news. If  any good news comes out of this, it will be that, if true, we might have more than five years to prevent a global disaster (to put it mildly); but obviously that depends on us.

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