2010-10-13 10:38:39New paper: Short lived uncertainty
John Cook


Puzzling response to new paper:


Skeptics are spinning it like it says "we cannot know climate sensitivity" because of uncertainty in forcings in the 20th Century. But we also calculate climate sensitivity from paleo records. But I haven't read the full paper, hidden behind a paywall.

Some skeptic takes:



2010-10-14 06:17:26interesting
Dana Nuccitelli

I'd like to read the whole paper too.  The Resilient Earth guy completely misunderstood the parts of the paper he quoted (my term for his take on the paper is "reading it through denial-colored glasses"), but at least he provided a useful contribution by quoting from the paper:

"Warming over the past 100 years is consistent with high climate sensitivity to atmospheric carbon dioxide combined with a large cooling effect from short-lived aerosol pollutants, but it could equally be attributed to a low climate sensitivity coupled with a small effect from aerosols. These two possibilities lead to very different projections for future climate change."

That's true if you only look at the temperature changes over the past 100 years in isolation.  But as you note John, there are numerous different ways that climate sensitivity is estimated.  Not just from paleoclimate data, but also from short-term responses to changes in volcanic and solar activity, just as a couple examples.  I really don't think it's a coincidence that they all overlap at 2 to 4.5°C for 2xCO2.

There's also evidence that aerosols do have a large effect, as I discussed in the mid-century cooling rebuttal.

So the skeptic take is basically "if we only consider this one piece of data, the climate sensitivity could be low!".

Here's the quote they really butcher:

"Of the short-lived species, methane, tropospheric ozone and black carbon are key contributors to global warming, augmenting the radiative forcing of carbon dioxide by 65%. Others—such as sulphate, nitrate and organic aerosols—cause a negative radiative forcing, offsetting a fraction of the warming owing to carbon dioxide."

From this they conclude "other factors account for 65% of the radiative forcing usually attributed to carbon dioxide", which quite obviously, is just plain wrong.  It's not news that other GHGs and black carbon cause warming in addition to CO2.  The key word in the quote is "augmenting".  And the non-CO2 feedbacks roughly cancel eachother out.

Based on these quotes I don't really see any new revalations in this paper.  Do you think it's worth doing a blog post about?  I could do one if somebody could provide the paper, but I'm not sure it's worthwhile.

2010-10-14 06:30:13full paper
Dana Nuccitelli
Oh actually somebody provided a link to the full paper in the Resilient Earth comments.  There's actually not much to it - it's just a commentary less than 2 pages long.  Anybody have input on whether this is worth doing a blog post on?  I wouldn't be able to get to it until the weekend.
2010-10-14 09:04:42


It' a commentary, not a regular paper. Skeptics fail to realize that, following the model restults presented, with a 2 °C sensitivity they get almost 3 °C of warming by 2100.

The idea to put under control first what can produce the maximum results is not new. Hansen a while ago proposed to phase out just carbon with a similar line of reasoning as this commentary.