[Global Change: 3753] Global warming, decade by decade

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David B. Benson

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Apr 20, 2010, 6:50:33 PM4/20/10
to globalchange
This
http://www.realclimate.org/index.php/archives/2010/03/unforced-variations-3/comment-page-12/#comment-168530
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 Arrhenius formula is still in use as quite a decent
approximation; see the appropriate section of IPCC AR4.

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.

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.

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Robert I Ellison

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Apr 21, 2010, 11:56:23 PM4/21/10
to globalchange
On Apr 21, 8:50 am, "David B. Benson" <dben...@eecs.wsu.edu> wrote:
> Thishttp://www.realclimate.org/index.php/archives/2010/03/unforced-variat...
> 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.

David B. Benson

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Apr 22, 2010, 6:24:47 PM4/22/10
to globalchange
On Apr 21, 8:56 pm, Robert I Ellison <rob...@robertellison.com.au>
wrote:
> > 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
On the contray, k and A were determined by the best fit to the GTA
data, a standard method of estimating parameters. Then the parameter
k is reporteed as OGTR for 2xCO2 being equal to k*ln(2). I don't care
what IPCC AR4, etc., say, this is the observed global temperature
response from the GISTEMP data.
> ... this is a little confusing.
It shouldn't be so give me a hint as to how I might better rewrite it
for clarity.
> The formula calculates changes in temperature based on CO2
> concentrations.
Yes.
> The answers are then back correlated with observed
> temperature.
Huh? The residuals are the differences between GTA and the values
from the formula. Everythng is absolutely standard and there is no
circularlity whatsoever. The method of detrmining the values of A and
k is to minimize the RMS error; once again this is vinilla parameter
estimation.
> The Arrhenius formulation is used by the IPCC to derived 'forcing' of
> trace atmospheric gases from empirical data.
If so, I didn't see it; the big AOGCMs don't use this approximation
being too crude for careful work.
> 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.'
So it depends upon the definition of abrupt. Fine. Then I'll say
that the global temperature change since the 1960s is abrupt. It
certainly is already impacting society, irrespective of definitions.
> 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.
All of that is treated as the Observed Global Temperature Resonse; all
of it.
> The only reason the correlation works is the assumption that all
> warming is from CO2 solely (implicit in the derivation of k)
Absolutely not. It is from CO2 and all fast feedbacks therefrom.

Robert I Ellison

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Apr 23, 2010, 6:10:23 AM4/23/10
to globalchange

> On the contray, k and A were determined by the best fit to the GTA
> data, a standard method of estimating parameters.  Then the parameter
> k is reporteed as OGTR for 2xCO2 being equal to k*ln(2).  I don't care
> what IPCC AR4, etc., say, this is the observed global temperature
> response from the GISTEMP data.> ...

So k (on the right hand side) is determined from the GISSTEMP record
of global temperature anomalies?

> The formula calculates changes in temperature based on CO2
> > concentrations.
> Yes.

You then calculate temperature anomolies and correlate the result with
the GISSTEMP record?

> The Arrhenius formulation is used by the IPCC to derived 'forcing' of
> > trace atmospheric gases from empirical data.
>
> If so, I didn't see it; the big AOGCMs don't use this approximation
> being too crude for careful work.

Sorry - I was thinking of the TAR - s 6.3.5 - simplified expressions.
4AR endorses the simplified expressions as still being pretty good.
Also with the net forcing - 4AR shows other forcings cancelling out as
you say.

> 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.'

> So it depends upon the definition of abrupt.  Fine.  Then I'll say
> that the global temperature change since the 1960s is abrupt.  It
> certainly is already impacting society, irrespective of definitions.

'What defines a climate change as abrupt? Technically, an abrupt
climate change occurs when the climate system is forced to cross some
threshold, triggering a transition to a new state at a rate determined
by the climate system itself and faster than the cause. Chaotic
processes in the climate system may allow the cause of such an abrupt
climate change to be undetectably small.'

http://www.nap.edu/openbook.php?record_id=10136&page=14

David B. Benson

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Apr 23, 2010, 3:31:33 PM4/23/10
to globalchange
On Apr 23, 3:10 am, Robert I Ellison <rob...@robertellison.com.au>
wrote:
> ...
>
> So k (on the right hand side) is determined from the GISSTEMP record
> of global temperature anomalies?
Yes. So is A, siumultaneously. Standard
parameter estimation method was employed.
>
> You then calculate temperature anomolies and correlate the result with
> the GISSTEMP record?
Yes, AE and then AEP are calculated, but
not correlated. The difference between the
estimate and the actual GICTEMP GTA is the
residual. The two parameters are estimated
so as to minimize the RMS of the residuals.
> ...
> threshold, triggering a transition to a new state at a rate determined
> by the climate system itself and faster than the cause.
Well, consider recent Artic sea ice melt.
Nobody seems to have predicted such a large
change would happen in 2007 CE.
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