[cogitator]

The atmospheric CO2 concentration is known, the number applied for forcing should be a fixed value if it were derived from basic science, as opposed to making a model fit.

Please comment on:

6.5.3. deltaF-deltaC relationships

and

IPCC Observations of Greenhouse Gas and Radiative Forcing Changes since 1750

In the latter, particularly note the summary entitled "Radiative Forcing".

[ancient_geezer]

You should have read the caveat, which is exactly what Hug & Barret have demonstrated experimentally:

6.5.1. Factors Affecting Greenhouse Radiative Forcing

A number of basic factors affect the behaviour of different greenhouse gases as forcing agents within the climate system (Shine et al., 1990). First, the absorption strength and wavelength of the absorption in the thermal infrared are of fundamental importance in dictating whether a molecule can be an important greenhouse forcing agent; this effect is modified by the overlap between the absorption bands and those of other gases present in the atmosphere. For example, the natural quantities of CO2 are so large (compared to other trace gases) that the atmosphere is very opaque over short distance at the centre of its 15mm absorption band. The addition of a small amount of gas capable of absorbing at this wavelength has negligible effect on the net radiative flux at the tropopause.

Also the equation:

DF = 6.3 ln (C/C₀) [Equation 19]

provided is empiricaly derived from justifying the IPCC models to adjust model outputs to reflect the contaminated surface temperature series, not from the basic physics of CO2 IR absorption characteristics.

Show me a derivation based in an actual controlled experiment backed up by physics not an equation reflecting the average of several incomplete and severly inadequate Global Climate models.

In the latter, particularly note the summary entitled "Radiative Forcing".

IPCC is known as much for what it doesn't say and leaves out than what it does.

1) Natural CO2 levels tend to follow, temperature change, they do not lead temperature. (due to release of CO2 from hydrates & dissolved CO2 in the oceans, increasing biomass, etc.) CO2 is an effect of temperature excursions in the atmosphere not a cause of such.

2) Much higher global temperatures with lower CO2 concentrations have existed in the past. CO2 concentration is poorly correlated with decadal & century changes in the climate.

Merely calling CO2 is a radiative forcing agent in a model does not make it a cause of global temperature change manifested in the physical world.