That had to be one of the funniest, silliest metaphors I’ve heard on this subject. In either scenario, the “bathwater” flows out of the tub. Sound like a negative feedback to me (i.e., the “water” doesn’t just keep rising and rising”). And the tub — who established the max volume/height, of the tub itself? Would that be the saturation level of atmospheric CO2 (the point at which additional CO2 can no longer add to any warming)? So we’re protecting the floor beneath the tub? What would that represent – space? oceans?

The global average seasonal amplitude is about 5 ppmv (just by coincidence about what is going on at MLO) for a global temperature amplitude of about 1 K, thus about 5 ppmv/K.

Does it not concern you that a global average contains a seasonal signal? Perhaps there is a good reason for this (one that springs to mind would be the land/ocean ratios of NH vs SH), but it concerns me that such a well examined and adjusted record displays seaonal variation when it is supposed to be a global metric. It seems to me that such variation shows a hemispheric bias to the NH. Perhaps, not being on the “inside” this is a trivial question, but I suspect many others here would appreciate an explaination if you know of one.

Secondly, given the statisticians “rule” of never using averages (or filtered data, if you prefer) in subsequent analysis (ref Briggs etc), would you care to comment on the caveats implicit in using yearly averages rather than monthly, or for that matter, daily or hourly numbers? Should we not see the same effects under any averaging conditions (temporal and/or spacial) and if we don’t, should we not suspect artifacts of the process to be responsible, rather than suggesting the filtered data shows us a “truth” that is not apparent in the un-filtered data?

Louis, the d13C level is known for different places, since about 1980:

http://www.ferdinand-engelbeen.be/klimaat/klim_img/d13c_trends.jpg

In ice cores these are measured for the glacials/interglacials and up to near present + in firn. In the upper oceans over the past 600 years. In all cases, there is some influence of temperature on the d13C level, but the spectacular decrease is completely in ratio with the emissions:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/sponges.gif

Thus in my opinion, there is little doubt that the emissions are the cause of the decline. The alternative that the natural emissions (of methane or other low 13C carbon) are the cause should have been in exact ratio with the emissions, and that is very unlikely…

Jack Barrett’s site makes intersting reading – but his section on the origin of fossil fuels is inaccurate – it’s basically Lyellian lyricism – and if that starting point is wrong, then so any deductions therefrom.

I pointed out in CCnet, in response to Richard Wakefield’s comments about peak oil etc, (read Benny’s CCnets for further information) that while indeed no one has created a natural diamond in the laboratory, no one produced high dalton number hydrocarbons in the lab either from simple increases in P and T. The Abiotic oilers have, however, and the published results are there for all to quibble over. This is simple fact to which no further reactions were published in CCnet.

The main belief is that the earth does not spontaneously generate hydrocarbons from the mantle region – hence no one bothers quantifying emission of CH4 from the ocean floors etc. AGW theory is based on a belief that all fossil fuels are recycled biomass but that assumption isn’t based on experimental evidence but on well argued specious rhetoric based on logical fallacies.

AGW is pseudoscience as a consequence, pseudoscience being one in which expert use of the scientific method is used on unverified starting assumption.

As a result the carbon cycle has to be questioned – and it is significant that the driving force for AGW had its origin in the UK with its Lyellian tradition of using the competence of a legal mindset to establish scientific “facts” in spite of the contradictory physical evidence.

The Barrett/Bellamy list omits the mantle emissions of carbon.

And I would like to see the d13/d12 ratio computed for more than one location too – Mauna Loa is, from a sampling theory POV, not representative of the Earth’s atmospheric composition wrt to CO2 isotopes.

That’s all I will post here on this topic for the time being.

There are different lists with the d13C level of different fuels, including methane. Here a few of them:
http://www.barrettbellamyclimate.com/page34.htm
http://homepage.mac.com/uriarte/carbon13.html

What is important is that vegetation is not a source of CO2, it is a sink, as there is oxygen production (thus CO2 incorporation).

Natural releases of methane don’t need to be enormous, as these have a very low d13C level (-40 per mil and lower), but to be the cause, the d13C level decrease should follow the methane increase in the atmosphere (as indication of natural CH4 emissions). But there is little increase in methane levels over the past decade…

Eli, thanks for the comment, I have read that somewhere too, but I wonder how large the influence could be, as the CO2 levels at similar altitude quite rapidely are mixed together within days to weeks, but a detailed comparison can give more insight.

Further, CO2 levels and d13C levels go in opposite way in the whole NH, be it more pronounced near ground than at altitude. That points to mainly vegetation as cause of the seasonal variation. Thus one need a quite huge difference between the continents for vegetation growth to make that difference…

One exception: You wrote – “Louis, one can make a differentiation through the 13C/12C ratio, if no other low 13C sources are helping. There is no sign for that, as the oxygen use proves. And aCO2 doesn’t stay in the atmosphere: the atmospheric mix (including a few % aCO2) is absorbed at the poles, but does return only after some 1,000 years. Thus only richer in 13C CO2 from the oceans (in the tropics) replaces aCO2 at a rate of 5.2 years half life time…

In order to substantiate this you need to list the CO2 sources according to their C13 content as measured.

I agree that burning hydrocarbons produces low C13 CO2.

But so also natural methane emissions, and which is greater?

I have been travelling for the last 2 days and will be on the move between two exploration projects some 2500 km apart for the next 3 weeks, so comments here will be infrequent.

Hence the lack of my comments does not mean I have accepted your reasoning – I just don’t have the time at present to get too involved in the aCO2 and NCO2 issue as I also have the next AIG News publication looming over the horizon as well.

So I will continue this discussion middle November unless I forget all about it.

ABTW Tim, differencing a noisy signal yields crap, something you learn in the first week of numerical analysis.