Re: [asa] Effect of CO2-Induced Global Warming on Antarctic Surface Mass Balance a Hundred Years Hence

From: Rich Blinne <rich.blinne@gmail.com>
Date: Sun Feb 04 2007 - 23:50:06 EST

On Feb 4, 2007, at 2:21 PM, Janice Matchett wrote:

> "I don't trust ANYBODY's predictions on sea level. There are two
> many free variables most specifically how much anthropogenic CO2
> there is going to be. The climate sensitivity numbers from the 2001
> report have been confirmed by more recent research. We don't know
> how successful or unsuccessful we will be at controlling CO2
> emissions or external factors such as possibly running out oil
> might have. We are discovering different negative (and positive!)
> feedback mechanisms that also affect the CO2 levels. Since 2001 we
> have better models where given the right inputs we can predict the
> effects but it is still GIGO (garbage in garbage out) because we
> still do not have accurate prediction of CO2 levels and probably
> never will." ~ Rich Blinne Mon, 11 Dec 2006 11:49:39 -0700
>
> ~ Janice :)

Since I have been quoted over and over and over, let's reset the
context. This was a reaction to a Daily Telegraph story of the leaked
AR4. Now I know that the prediction was based upon different
scenarios of CO2 emissions. So, my point above is not valid since I
was unaware that the predictions were scenario-based. Therefore, I
publicly retract my comment. My retraction does give me a chance to
"score" the original article for accuracy now that we can compare the
leaks with the actual AR4 SPM.

First prediction:

> The IPCC has been forced to halve its predictions for sea-level
> rise by 2100, one of the key threats from climate change. It says
> improved data have reduced the upper estimate from 34 in to 17 in.

In order to get that number it needs to get the following number from
TAR.

> The region delimited by the outermost lines shows the range of all
> AOGCMs and scenarios including uncertainty in land-ice changes,
> permafrost changes and sediment deposition.
>

  It's not eve the worst case SRES scenario. It's worst-worst case.
Note: 34 inches = 86.4cm See http://www.grida.no/climate/ipcc_tar/wg1/
fig11-12.htm to see that in order to get the number involved you need
to get the outermost line rather than any of the scenario average.

How was 17 in. determined? By claiming the so-called worst case for
scenario was B2. Note 17in= 43cm. But wait. The worst case scenario
was A1F1 as shown below quoting from AR4.

B1 scenario 0.18m 0.38m
A1T scenario 0.20m 0.45m
B2 scenario 0.20m 0.43m
A1B scenario 0.21m 0.48m
A2 scenario 0.23m 0.51cm
A1FI scenario 0.26m 0.59cm

What does AR4 really say?

> Model-based projections of global average sea level rise at the end
> of the 21st century (2090-2099) are
> shown in Table SPM-2. For each scenario, the midpoint of the range
> in Table SPM-2 is within 10% of the
> TAR model average for 2090-2099. The ranges are narrower than in
> the TAR mainly because of improved
> information about some uncertainties in the projected contributions.

So much for halving the prediction of sea level rise. The prediction
was retained with greater accuracy. Richard Gray must have taking
disingenuous statistics lessons from Michael Crichton.

Prediction Number 1. Score 0

> In a final draft of its fourth assessment report, to be published
> in February, the panel reports that the level of carbon dioxide in
> the atmosphere has accelerated in the past five years. It also
> predicts that temperatures will rise by up to 4.5 C during the next
> 100 years, bringing more frequent heat waves and storms.

As Pim noted when this was originally posted, this betrays a complete
misunderstanding of climate sensitivity which is defined as the
increase in temperature for a doubling of CO2. Again from AR4:

> The equilibrium climate sensitivity is a measure of the climate
> system response to sustained radiative
> forcing. It is not a projection but is defined as the global
> average surface warming following a doubling of
> carbon dioxide concentrations. It is likely to be in the range 2 to
> 4.5C with a best estimate of about 3C,
> and is very unlikely to be less than 1.5C.

The worst case business as usual scenario (A1F1) is 4.0 degrees C,
not 4.5.

Predication Number 2. Score 0

> The authors also state that the climate is almost certain to warm
> by at least 1.5 C during the next 100 years.
Again a prediction based on misunderstanding of climate sensitivity.
See AR4 quote above.

Prediction Number 3. Score 0

> It also says that the overall human effect on global warming since
> the industrial revolution is less than had been thought, due to the
> unexpected levels of cooling caused by aerosol sprays, which
> reflect heat from the sun.
What does AR4 say?

> The understanding of anthropogenic warming and cooling influences
> on climate has improved since
> the Third Assessment Report (TAR), leading to very high confidence7
> that the globally averaged net
> effect of human activities since 1750 has been one of warming, with
> a radiative forcing of +1.6 [+0.6
> to +2.4] W m-2. (see Figure SPM-2). {2.3. 6.5, 2.9}
>> 7 In this Summary for Policymakers the following levels of
>> confidence have been used to express expert judgments on the
>> correctness of the underlying science:
>> very high confidence at least a 9 out of 10 chance of being
>> correct; high confidence about an 8 out of 10 chance of being
>> correct.
> The combined radiative forcing due to increases in carbon
> dioxide, methane, and nitrous oxide is +2.30
> [+2.07 to +2.53] W m-2, and its rate of increase during the
> industrial era is very likely to have been
> unprecedented in more than 10,000 years (see Figures SPM-1 and
> SPM-2). The carbon dioxide radiative
> forcing increased by 20% from 1995 to 2005, the largest change for
> any decade in at least the last 200
> years. {2.3, 6.4}
> Anthropogenic contributions to aerosols (primarily sulphate,
> organic carbon, black carbon, nitrate and dust)
> together produce a cooling effect, with a total direct radiative
> forcing of -0.5 [-0.9 to -0.1] W m-2 and an
> indirect cloud albedo forcing of -0.7 [-1.8 to -0.3] W m-2. These
> forcings are now better understood than at
> the time of the TAR due to improved in situ, satellite and ground-
> based measurements and more
> comprehensive modelling, but remain the dominant uncertainty in
> radiative forcing. Aerosols also influence
> cloud lifetime and precipitation. {2.4, 2.9, 7.5}
> Significant anthropogenic contributions to radiative forcing come
> from several other sources. Tropospheric
> ozone changes due to emissions of ozone-forming chemicals (nitrogen
> oxides, carbon monoxide, and
> hydrocarbons) contribute +0.35 [+0.25 to +0.65] W m-2. The direct
> radiative forcing due to changes in
> halocarbons8 is +0.34 [+0.31 to +0.37] W m-2. Changes in surface
> albedo, due to land-cover changes and
> deposition of black carbon aerosols on snow, exert respective
> forcings of -0.2 [-0.4 to 0.0] and +0.1 [0.0 to
> +0.2] W m-2. Additional terms smaller than +0.1 W m-2 are shown in
> Figure SPM-2. {2.3, 2.5, 7.2}
> Changes in solar irradiance since 1750 are estimated to cause a
> radiative forcing of +0.12 [+0.06 to +0.30]
> W m-2, which is less than half the estimate given in the TAR. {2.7}

Note aerosols, not aerosol sprays. Indirect aerosol forcing was -2 W
m-2 in TAR, so the cooling effect is less, not more in AR4. Note that
Janice's favorite, radiative forcing, is less than half the estimate
of TAR. Compare the magnitude with the anthropogenic contribution and
see that it's overwhelmed by the human contribution. Very high
confidence means greater than 90% confidence of being correct. The
first paragraph above should be everybody's takeaway from AR4.

Prediction Number 4. Score 0.

One final comment. Note this:

> The IPCC report, seen by The Sunday Telegraph, has been handed to
> the Government for review before publication.
So, there was no need to guess. They had the report yet they botched
it greatly because they cannot do science reporting to save their
lives. Sadly, this is the norm rather than the exception for the
Telegraph. It's no wonder that Mark Steyn, Rush Limbaugh, and the
Wall Street Journal Opinion Page lean on it so heavily.

Final Grade. F

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Received on Sun Feb 4 23:50:49 2007

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