On Apr 21, 8:50 am, "David B. Benson" <dben...@eecs.wsu.edu
> came up on the "Swedish" thread, but as the reply
> feature is missing, I'll answer Robert by starting a
> new thread.
> The formula used is quite clearly
> AE(d) = k(lnCO2(d-1) - lnCO2(1870s)) - GTA(1880s)
> but unfortunately the obvious right parenthesis was
> missing. Now the conversion factor k is not that
> orignally used by Arrhenius but is determined by the
> best fit to the data, as is later explained in the link.
The formula seems to have an observed temperature term on the right
hand side but as the method derivation of k was unexplained - other
than a vague reference to observed temperature increase for a doubling
of CO2 - this is a little confusing. I dervived a similar value (2.3
as against 2.28) using the Arrhenius factor (gamma) for carbon dioxide
of 5.35 (as used in the IPCC)and using the observed century warming
for the observed increase in CO2 for a second factor to convert
forcing to a change in temperature.
The formula calculates changes in temperature based on CO2
concentrations. The answers are then back correlated with observed
temperature. This is what I described as circular reasoning.
> The Arrhenius formula is still in use as quite a decent
> approximation; see the appropriate section of IPCC AR4.
The Arrhenius formulation is used by the IPCC to derived 'forcing' of
trace atmospheric gases from empirical data.
> As for abrupt behavior, that is seen in Greenland
> ice cores, representation of the northern North
> Atlantic due to abrupt changes to those massive
> portions of the cryosphere which we no longer
> have with us.
The US National Academy of Science disagrees - 'Modern climate records
include abrupt changes that are smaller and briefer than in
paleoclimate records but show that abrupt climate change is not
restricted to the distant past.' 'Large, abrupt climate changes have
repeatedly affected much or all of the earth, locally reaching as much
as 10°C change in 10 years. Available evidence suggests that abrupt
climate changes are not only possible but likely in the future,
potentially with large impacts on ecosystems and societies.'
> As for all othr forcings, in the notes I explained
> why those can be ignored for the data of the
> last 13 decades; all such, positive and negative,
> cancel each other.
The forcing from CO2 - easily calculated using gamma = 5.35 and CO2
concentration changes over time - is 1.6 W/m2. The net forcing
according to the IPCC is 2.4 W/m2. You also need - in order to
plausibly model climate responses - to add in feedbacks of clouds and
water vapour at a minimum.
The only reason the correlation works is the assumption that all
warming is from CO2 solely (implicit in the derivation of k)and the
consequential aforementioned circular reasoning.