Re: [asa] Science Waffles on Warming

Again it seems that a cursory reading of the materials involved would
have avoided yet another embarassing myth.

From the article in Nature Reports: Climate Change we actually read:

<quote>The century-long lifetime of atmospheric CO2 and the
anticipated future decline in atmospheric aerosols mean that
greenhouse gases will inevitably emerge as the dominant forcing of
climate change, and in the absence of a draconian reduction in
emissions, this forcing will be large.</quote>

So, the role of CO2 is well accepted so what is the article about?

As was explained in a previous posting, the ICPP does not 'predict'
but rather takes realistic scenarios to determine the potential range
of impacts. In order to do actual predictions more accurate
information as well as representations of mechanisms and feedback need
to be developed.

<quote>In its latest report on the physical science basis of climate
change1, the Intergovernmental Panel on Climate Change (IPCC) moves
increasingly beyond detecting global change and attributing it to
human activity, into quantitative assessment of the ability to
forecast the prospective change in climate that would result from
future emissions scenarios.</quote>

The researchers warn that

<quote>. This new direction requires careful analysis of the
uncertainties associated with assessing future climate change, and the
new report is explicit in its definitions. In a departure from
previous reports, the latest assessment gives a best estimate of
climate sensitivity — the increase in global mean surface temperature
that would be expected to result from a doubling of atmospheric CO2
levels. The present best estimate of 3 °C is the same as that given by
a US National Research Council panel in 1979, but it now comes with a
well-defined confidence interval. Specifically, the report states that
the sensitivity "is likely to be in the range 2 °C to 4.5 °C," where
"likely" is defined to mean a greater than 66% probability that the
actual quantity is within the stated range.</quote>

Since the warming effects of some greenhouse gases is nearly balanced
by the cooling effects of anthropogenic aerosols, CO2 remains the main
forcing but... the uncertainties involved are quite large since we
subtract to almost equal numbers.

The researchers then point to an inconsistency that needs to be
resolved, namely the fact that simulation runs show a factor of 2
increase while the forcing scenario would suggest a factor of 4.

Feel free to read the actual article rather than the spin

http://www.nature.com/climate/2007/0707/full/climate.2007.22.html

and decide for yourself. Remember that the 'rising icon' does not
refer to the fact of anthropogenic causes for the global warming, but
rather to a technical detail. Important but also irrelevant to the
fact of Global Warming. As is the case with evolution deniers, much is
made by global warming deniers of internal discussions about these
issues by scientists. What some may see as a weakness, however is a
strength of science.

In Christ

On 7/9/07, Janice Matchett <janmatch@earthlink.net> wrote:
>
>
> July 08, 2007
> Science Waffles on Warming By James Lewis
> http://tinyurl.com/32byds
>
> ~ Janice ... ( For those interested, my 3 posts begin here:
> http://www.freerepublic.com/focus/f-news/1862976/posts?page=23#
> 23 )
>

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Received on Mon, 9 Jul 2007 09:50:08 -0700