Temperature Trends and Carbon Dioxide: A Note from Cohenite
Posted by Cohenite, October 5th, 2008 - under Community, Opinion.
Tags: Climate & Climate Change
Hi Jennifer,
Looking at the temperature trends from 1900-2008, it is not clear that there is a carbon dioxide signal.
In a recent post I looked at how base periods can create an artificial upwards temperature trend;
http://www.jennifermarohasy.com/blog/archives/003303.html#comments
The 20thC featured 2 El Nino dominated climate patterns (+ve PDO), and one La Nina phase (-ve PDO) from 1940-1976. The temperature trend in the first +ve PDO is almost identical to the temperature trend in the second +ve PDO;
http://tamino.files.wordpress.com/2008/01/smooth.jpg
The similar slopes at the beginning and end of the 20thC represent warming WITHIN the +ve PDO’s, while the lower starting point for the first +ve PDO is an artifact of the 1951-1980 GISS base period. The GISS graph also shows post 1998 temperatures as increasing. This is contradicted by the other temperature data collectors, which show a decreasing trend consistent with the emergence of another –ve PDO post 2001 (discussed below). The issue is, what would be the temperature trend be with ENSO removed and what part would CO2 play in causing that residual trend?
In a recent paper, David Douglass and John Christy isolate a temperature trend due to CO2 forcing, independent of feedback (ie: the enhanced greenhouse) and natural factors such as ENSO and volcanic effect;
http://arxiv.org/ftp/arxiv/papers/0809/0809.0581.pdf
Douglass and Christy’s (DC) study is based on 1979-2008 UAH non-surface data. After extracting ENSO, volcanoes and allowing for latitude band effects, they isolate a CO2 signal of+0.070g/decade; where g is the gain due to any feedback. In respect of ‘g’ DC note “there is general agreement among climate scientists for the case of no feedback”. (p3).
DC estimate there is an undeducted solar irradiance forcing (SF) of 20% (p10), or +0.014C per decade. This generally agrees with AR4’s figure for SF of +0.12Wm-2, which translates to a temperature of +0.16C per century (see Chp 2 pp 187-193). AR4 has reduced this SF figure from TAR’s estimate of +0.3Wm-2, or a temperature increase of approximately 0.4C PC (see 6.11.1.2; FIG 6). The AR4 amount for SF is based on the period from 1750-present, but, according to FIG 2.17, the bulk of the SF has occurred in the 20thC. DC’s SF estimate seems about right then.
So, deducting DC’s SF from +0.07 - +0.014 = +0.056C PD for a CO2 signal in the period 1979-2008.
However, DC note that “the global atmospheric temperature anomalies of Earth reached a maximum in 1998 which has not been exceeded during the subsequent 10 years”. (Abstract). As noted above, GISS is showing increasing post 1998 temperature, so what is happening in the 21stC?
In an analysis based on the period 2001-2008 Lucia also removed ENSO from 5 of the temperature indices;
http://rankexploits.com/musings/wp-content/uploads/2008/07/ipcc-falsifies-gavin.gif
For a full discussion of Lucia’s analysis see;
http://rankexploits.com/musings/2008/gavin-schmidt-corrects-for-enso-ipcc-projections-still-falsify/
Lucia has applied 2 statistical approaches to all post 2000 data, GISS, HadCrut, NOAA, UAH and RSS, and obtained a combined result for OLS of -0.3C(+-1.6) PC, and for Cochrane-Orcutt, -0.6C(+-1.5) PC.
Averaging the 2 methodologies gives an ENSO free temperature trend for 2001-2008 of-0.45C or a decadal trend of -0.045C. Lucia has not adjusted for volcanoes as there were no proximate eruptions, or for SF. If an offset for SF of +0.014C is made, this would produce an underlying cooling trend of -0.059C PD, presumably due to CO2.
So, in summary:
1. AR4 notes that “Most of the observed increase in global average temperatures since the mid-20thC is very likely due to the observed increase in anthropogenic gas concentrations” (Executive Summary, CHP 2)
2. AR4 allocates a Radiative Forcing to the combined GHG’s of 2.63Wm-2; CO2 is allocated a RF of 1.66Wm-2, or 2/3’s of the total RF.
3. The RF for CO2 is estimated by AR4 to lead to an increase in temperature from a doubling of CO2 of ~ 3C. CO2 has increased ~ 40% since 1900. This should have produced a temperature increase of 1.2C or 0.12C PD.
4. Applying AR4’s quotient for CO2 RF of 2/3 to the findings of DC and Lucia we obtain the following CO2 signals; DC = +0.056 3 x 2 = + 0.037C PD for the period 1979-2000; for Lucia = -0.059 3 x 2 = -0.039C PD for the period 2001-2008.
5. A further complication applies to the first ½ of the 20thC temperature trends. There was less CO2 and GHG’s prior to 1976, yet the temperature trends at the beginning of the 20thC, as shown by GISS above and HadCrut are very similar; http://i32.tinypic.com/2s01m5y.jpg
6. Then, of course, there is the 30 year decline in temperatures from 1940-1976 when CO2 was increasing.
7. DC and Lucia have found a CO2 signal. It is inconsistent, I draw 3 conclusions;
a) The inconsistency found by DC and Lucia reflects the contrary movements of CO2 and temperature apparent during the rest of the 20thC and history generally.
b) IPCC forcing estimates for CO2 are grossly over-inflated. Even more so when enhanced greenhouse, “g”, is quantified with +ve feedback.
c) In respect of “g”; if the CO2 signal is larger than that found by DC and Lucia, then –ve feedbacks would have to be much greater. These –ve feedbacks cannot be aerosols (see DC p 12), or ENSO as suggested by Keenlyside et al. Perhaps climate sensitivity to SF is greater than AR4 assumes.
Cheers, Cohenite
Newcastle, Australia
[...] and in a fairly technical note, already posted at the community webpage of this blog, and entitled ‘Temperature Trends and Carbon Dioxide’ suggests that there is no evidence for a contribution from carbon dioxide to global temperatures [...]
cohenite said…”…they isolate a CO2 signal of+0.070g/decade; where g is the gain due to any feedback”.
The whole feedback thing is a mess. Feedback DOES NOT cause gain, it controls it. The gain has to be inherent in the system.
For example, in an electronic amplifier, an active device like a transistor provides the gain. You don’t get something for nothing, however, the gain is provided by current from the power supply. The active device acts as a transducer that causes a larger output amplitude swing in the current from the power supply than the swing of current/voltage in the input signal.
Without feedback, the amplifier works perfectly well but it can be unstable. Sampling a small part of the output signal and feeding it back to the input signal has two distict effects.
If the sampled output is fed back so as to enhance the input signal (add to it) the amplified signal gets larger. Therefore, the sampled feedback gets larger, and a runaway effect occurs. I would imagine that is Hansen’s tipping point.
If the sampled signal is fed back so it subtracts from the input signal (negative feedback) the amplified signal is smaller. Subsequent cycles of feedback don’t lower the output without bounds, however, because the amplifier does not amplify in a negative direction. Negative feedback is used to stabilize amplifiers over a frequency range.
All servo systems work like this and I can’t imagine how it has been applied to the atmosphere. Where does the amplification come from in the first place? The opposite of an amplifier is an attenuator and it is comprised of passive devices (no ability to amplify) such as resistors, inductors and capacitors.
In order for gain to be applicable in the atmosphere, there would need to be a device that increased heat. It would require an external source of energy to do that. The source of the heat initially is the Sun, but it can’t be regarded as an amplifier because it’s not part of a closed system and it’s output cannot be varied by a fed back signal.
Gordon; DC address the feedback issue on p3 of the paper; this is where Miskolczi comes in with declines in RH to adjust for slight temp increases; as I say in a post over at the link to the paper, greenhouse, as conceived by AGW, is a fallacious concept; it doesn’t mean heat; it means temp modulation; it maintains equlibrium within the atmosphere; and the fact that RH is declining lends considerable weight to the argument that the increase in CO2 levels is natural.
“In order for gain to be applicable in the atmosphere, there would need to be a device that increased heat. It would require an external source of energy to do that. The source of the heat initially is the Sun, but it can’t be regarded as an amplifier because it’s not part of a closed system and it’s output cannot be varied by a fed back signal.”
The transformer in the power supply puts out a fixed voltage, too. But the amplifier still works.
Yeah, so where is the amplifier in the atmosphere?
I think we need to introduce some fun into all of this.
I think that anyone who looks at the evidence/historical record (not dodgy sexed up computer dossiers, sorry models!) will quickly understand that the IPCC and AGW alarmists are dead meat. However, like any injured animal they’re at their most dangerous when cornered, which is why we have the Gore-oracle blaming recent US floods on AGW.
So, lets take bets on when the whole AGW hoax is going to collapse. My money’s on Autumn 2009 when we had a colder than normal winter and another wet and cold summer.
Bickers,
My guess for when the whole AGW house of cards falls is close to your Autmn 2009. By then the latest data on the cosmic ray - cloud - climate hypothesis will be in, providing quantitative data. The particle accelerators at CERN will be starting up next spring when the winter European electricity loads are reduced.
Since AGW is a religion it will not collapse. They will just say that CO2 produces Global Cooling or come up with some other mumbo jumbo “scientific matrix” as they are now doing in Australia which is now experienciing one of it’s harshest winters ever. The gameplayers of AGW are radical green globalist and they will not stop until they are totally out.
Since AGW is a religion it will not collapse. They will just say that CO2 produces Global Cooling or come up with some other mumbo jumbo “scientific matrix” .
SJT,
In an electronic circuit, there are many amplifiers (transistors are amplifiers that amplify a small voltage to a higher one -but always below -or up to- the rated voltage for the circuit).
Only transformers amplify voltage. Amplifiers amplifes the power output (watts, when doing any work, or amperes, related to current intensity).