Re: [asa] Lesson in science: Soot and global warming

From: PvM <>
Date: Wed May 23 2007 - 00:50:02 EDT

The problem is two fold, first of all Davescot ignored the ICPP
document which outlined the sources for their estimates, but he also
ignored the Hansen paper. In fact, the figure he quotes is one of a
series of 2, the second one shows a more accurate and relevant
overview of the forcings and shows .25 for fossil fuels and -0.22 for
bio mass.

It's a good lesson I believe that shows how preconceived notions about
the IPCC led Davescot to jump to a conclusion not warranted by either
the IPCC document nor the original paper.

And that's the difference between skeptics and some global warming
deniers I believe.

On 5/22/07, Rich Blinne <> wrote:
> On 5/22/07, Rich Blinne <> wrote:
> >
> >
> > How does the IPCC handle Hansen et al 2005?
> >
> >
> > > Hansen et al. (2005) allowed the albedo change to be proportional to
> local BC deposition according to Koch (2001) and presented a further revised
> estimate [from Hansen et al 2004] of 0.08 W m2. They also suggested that
> this RF mechanism produces a greater temperature response by a factor of 1.7
> than an equivalent CO2 RF, that is, the 'efficacy' may be higher for this RF
> mechanism (see Section This report adopts a best estimate for the
> BC on snow RF of +0.10 0.10 W m2, with a low level of scientific
> understanding (Section 2.9, Table 2.11).
> >
> >
> > This means that the IPCC actually gives a higher estimate of BC in snow
> forcing than Hansen et al 2005.
> Correction: I misread the IPCC paragraph. The "equivalent" RF (.08 x 1.7) is
> within the error bars of the IPCC best estimate.

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Received on Wed May 23 00:50:14 2007

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