A Critique of IPCC-FAR (4th Assessment Report 2007)
S. Fred Singer,

A Critique of IPCC-FAR (4th Assessment Report 2007)
(This critique is based on the April 2006 draft of the Summary for Policymakers)
S. Fred Singer, June 10, 2006
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Contents:
1. Radiative Forcing
2. Observations
3. Paleo-climate
4. Attribution
5. Projections
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1. Radiative Forcing

Carbon Dioxide: Fig. SPM-1 shows that forcing from CO2 increased by 1.6 W/m2 in the past 250 years - from zero to 1.6 - after little change in the past 8000 years But the figure is misleading since it does not show the total greenhouse forcing of about 320 W/m2. Thus the increase is really only 0.5%.
Another peculiar feature: The same CO2 curve is used for concentration (ppm) and forcing, implying a linear relationship. But it is well known to be logarithmic. I suspect that IPCC overestimates both present and future forcing.

Solar Forcing: Fig. SPM-2 shows a minor solar forcing based solely on changes in irradiance. But we have excellent evidence for a much larger forcing from solar-modulated cosmic rays. The IPCC denies this (see TS.2.4).

Aerosols, Ozone: These forcings show large geographic and temporal variations. Global averages can be severely misleading, esp. in attribution studies.

2. Observations

Temperatures: Urban heat island effects are dismissed; land-use changes are not even mentioned. Sea-surface temperatures (SST) face special problems: They are "glued together" from a variety of instruments that show poor geographic distribution. A fundamental problem exists for SST in that downwelling IR radiation cannot penetrate beyond a thin (~10 micron) skin layer.
No mention is made of the fact tht many proxy data show no warming since 1940.

Sea Level: SL rise does not show an acceleration in the 20th century - in spite of strong warming during 1920-40 (cf my discussion in Hot Talk, Cold Science, p. )18). Fig. 3b shows sea levels rising but they don't tell you that this is just the rate that has been ongoing for several 1000 years -- roughly 18cm per century
Mountain Glaciers: No mention of the fact that about half have stopped shrinking since 1940 (see TAR , p 128)

3. Paleo-climate

FAR no longer supports the "Hockeystick," featured in TAR. I quote from the SPM (p.9):
"Some recent studies indicate greater variability in NH temperatures over the last 1000 years than reported in TAR ... " As you may recognize, this re-establishes the Little Ice Age, which the "Hockeystick" had abolished.

But FAR also suggests: "Average NH temperatures during the second half of the 20th century were ... likely the warmest in the past 1000 years."
This claim, based only on poorly calibrated tree-ring data, goes against actual data with thermometers in ice-core boreholes (Dahl-Jensen) and isotope data of ice cores (Cuffey); both show the Medieval Warm Period much warmer than the present. The IPCC also ignores the abundant historical evidence for Medieval warmth.
See also http://www.sepp.org/NewSEPP/NAS%20Hockeystick.htm

4. Attribution:

Global Temperature for 20th Century: The IPCC reports (TAR-2001) and (FAR or AR4--2007) both claim that models can "explain" the global-mean temperature history of the 20th century. But this "fit" includes at least four adjustable parameters --and many more that are less obvious:
1. Climate sensitivity, i.e., temperature increase for CO2 doubling
2. Aerosol emission history -- intensity, temporal and geographic distribution
3. Solar irradiance -- and appropriate sensitivity
4. Volcanic emissions, geographic distribution of particulates, their lifetime, etc
Item #1 is the most obvious one since elsewhere in the IPCC report climate sensitivity varies between 1.5 and 4.5 degC.
To be more convincing, the match between models and temperature data should not be for just the Global Mean but for each latitude belt (or at least for tropics, NH and SH) -- USING THE SAME ADJUSTABLE PARAMETERS.

Precipitation: The model "skill" for precipitation is so bad, they don' t even report it

Geographic Distribution of Temperature: Current GH models don't account for NH/SH differences, for Antarctic cooling, and why Arctic temperatures were highest in the 1930s.

Altitude Variation of Temperature: Models predict that temperature trends should increase with altitude, about doubling in the tropics. Observations show trends decreasing with altitude - or flat.

5. Projections (Sea Level)

Singer (in HTCS 1997) ........................18 +/- 5 cm
IPCC AR4 (2007)……………………14--43 cm
NAS (2005) .........................................10-90 cm
Gore (2006) .........................................60 cm (but occasionally much greater)
Hansen (2006)......................................5000 cm, corrected to 1000 cm (ABC interview)