I read the Real Climate article and I was disappointed, because I thought of the same thing you did: How can one say that the lower C-13/C-12 ratio can be isolated to the burning of fossil fuels, except by the coincidence of timing as they claim? I thought they were going to include C-14 in the analysis, but they didn’t really.

The way I’ve picked out good scientific theories in the past is if the scientists presenting them can connect the dots: “A leads to B leads to C”. They can show the chain of cause and effect, either based on known phenomena or measurements. I’ve never seen this with the AGW crowd. What I’ve proposed to them is if they really want to prove their point they should measure all of the outputs both man-made and natural. This could be done in a statistically valid way since measuring every single source would be next to impossible. With the man-made sources they could look at inputs of fossil fuels (they could look at historical company records) and calculate outputs of CO2. They could check the output calculations against the actual measurement of CO2 to see if they’re conception of outputs is good. They could look at the Earth as a giant operating system, and take that sort of analytical approach to it, accounting for and isolating specific carbon categories. I agree it would be complex, maybe too complex for us humans to analyze. Maybe computers could help, but not in the way they’ve been used, which is just fooling ourselves. If and when they got this right then they could say that X% is man-made, and Y% is natural. By only looking at the C-13/C-12 ratios it seems to me they’re only looking at effects that could be caused by a number of factors, but they assume (again) that it must only come from one source. I wouldn’t know unless I actually look at the papers. Some of the science may be good in terms of adding some knowledge to what we know, but the conclusion sounds suspicious.

I’ve run into the same thing you’ve talked about that “there is no unique signature for industrial carbon” when talking to others who believe in AGW. Several years ago I ran into this curious argument about how ethanol was “carbon-neutral”, which has turned out to be the biggest joke, because it’s anything but, due to the amount of energy that goes into corn ethanol production. But before the ethanol subsidies went into place I finally asked these people, “Why is ethanol more carbon-neutral than oil? Plants can’t tell the difference between carbon that comes from ethanol and what comes from fossil fuels.” I didn’t get an answer. It all turned out to be marketing hype.

Well the bristlecne pines of eastern California proved that C14 production is anything but constant; and world histories were rewritten as a result of that re-calibration of the C14 time scale.

So c14 variations could be nothing more than the now known wide variation in cosmic ray flux on earth.

Also the C12/C13 isotope mix doesn’t prove that all the increase in atmospheric CO2 is from fossil fuel burning. ALL that it shows is that a newer source of carbon, that may have an anomalous C13/C12 ratio, is being introduced into the atmosphere. There’s no way to prove that any specific C12 or C13 molecule came from a fossil fuel or from soem other source.

If we started burning a new source of fossil fuel that contained 5% of Argon, and we just vented the argon, then the atmospheric argon abundance would increase; which doesn’t prove that all of the increased CO2 in the atmosphere comes from our new fossil fuel/argon source; just that we are burning some of it.

Besides fossil fuels are supposed to be old plants aren’t they; so why would they have a carbon signature that is different from modern wood or other natural sources of carbon.

Isotope ratios get a lot more hype than they deserve. The isotope carbon ratio in carbonate rocks should reflect what was in ancient oceans and their ancient aquatic life forms.

Which does not mean that I don’t accept that human use of fossil fuels may be increasing atmospheric CO2; but by how much compared to other sources like the mediaeval warming period 800 years ago.

All of which is irrelevent anyway, because CO2 from whatever source has very little to do with the climate of the earth. so who cares where it comes from.

CO2 sequestration is also oxygen sequestration.

Besides anew study shows that the earth is slowly running out of cO2, and eventually the CO2 in the atmosphere is going to be so low, that plants and eventually all life on earth will simply sufficate. They are proposing to reduce the earth’s atmospheric pressure to create a higher altitude atmosphere in which we apparently can get by with less CO2.

This new CO2 suffocation disaster, will hit the planet between 100 million and 1 billion years from now. So we better get ready for living with a lower atmospheric pressure.

George

I have heard of this logarithmic temperature response to increased CO2. Bob Carter talked about it, and he said “This is not controversial”. Your factoid about there being vastly more carbon held in sedimentary rocks than in fossil fuel reserves does help me put this in perspective. The alarmists keep talking about the “limited carrying capacity” (that’s my term) of various carbon sinks.

The reason I got into this at all was over a 5% figure I used for industrial contribution to the CO2 in the atmosphere. I remember hearing at least one non-alarmist climatologist giving a figure like this.

I tried getting this “professor” (I’m assuming) to look at contrary evidence, such as the Medieval warm period, or the temperature decline from the 1940s to the 1970s (while CO2 concentration was rising), and he ignored it every time. He kept going back to a “time correlation” between the rise in non-radioactive CO2 to the rise in temperature, as if that proved the whole thing. He used terms like “scientifically proven” and “fact” for this.

At first he didn’t even talk about the “carbon dating” technique. He just said it was “reasonable” to link the two (rise in CO2 with temperature), and that there was a 21% increase in CO2 from the 19th century up to the present day, and that it was totally attributable to industrialization. I said that statement was just as valid as the Aztecs saying that the Sun rose because they made a human sacrifice to it every day. I thought the analogy was very apt–correlation with human action. It’s scary to think that there might be scientists who think like this. My science teachers in school taught us to be wary of drawing conclusions from correlations. Apparently he didn’t get that.

Anyway, the thing about “carbon dating” proving what he was talking about grabbed my attention, because I had never heard of it before. After getting some clarification on here I think he was confused about the terminology. I was looking at information on carbon-14 measurement (which is what one would naturally look for when looking up “carbon dating”) when I should’ve been looking at the ratio between carbon-12 and 13. I did find an article on “Real Climate” that talks about this ratio (at http://www.realclimate.org/index.php?p=87). This may have been where he got his information. It draws the same conclusion about time correlation, and references some (offline) journal articles that talk about the data.

Thanks to all. I got a lot more helpful and accurate information from you guys than I did from the “professor”.

But the proof is not as strong as claimed. If the oceans are evolving CO2 and man injects a significant amount in the atmosphere it will look like man is responsible because the addition of man made CO2 will suppress some evolution of CO2 from the ocean due to the partial pressure balance.

Air Con: The Seriously Inconvenient Truth About Global Warming

Mark,
I think if I recall correctly that the IPCC estimates that about half of man’s CO2 emissions show up as an increase in concentration of atmospheric CO2 and the rest disappears into the system (possibly dissolves in oceans, biological uptake etc.) So your scenario of the total of man’s CO2 emissions going entirely to increasing atmospheric CO2 concentration is not even a mainstream AGW hypothesis.

But say it was true. Your fears of the atmospheric concentration of CO2 going ever upward is not possible when you realize there is a limited amount of fossil fuels available to burn. The carbon in fossil fuels is miniscule compared to the vast carbon storage in sedimentary rocks and carbon compounds dissolved in the oceans. Without the existance of a fabled positive feedback factor in the computer climate models, you could burn all the CO2 from all the world’s fossil fuel reserves and would not change the climate significantly. In a way, it is a mote point as to whether man is increasing the concentration of CO2 in the atmosphere if the increase has little effect on climate.

Remember that the global temperature response to CO2 increase is approximately logarithmic within present and projected concentrations. Each doubling of concentration yields a more or less linear temperature increase. In at the present concentration of 380 ppm, CO2 doubling would increase the global temperature about 1C thereabouts, depending on who you read. And the next doubling would yield the same 1C increase. We expend all fossil fuels long before we would burn up the earth. Projections of disastrously larger increases in global temperature depend on the supposition of a positive feedback factor for which there appears to be very weak scientific justification to date.

The reason I asked about the C-14/C-12,C-13 ratio is my understanding has been that CO2 from industrial sources has been so tiny as to be background noise, about 5% of the 383ppm CO2 concentration. If as this “professor” (that’s still my operating assumption) said this ratio shows that the CO2 increase we’ve seen is due (perhaps solely–he suggests that) to industrial activity, then that changes what I thought I knew about this aspect of the debate, and it might change my POV on the AGW issue. For if the CO2 increase was solely due to industry then that means the amount of it could continue increasing ever upward, and we could project that while CO2 hasn’t had an effect on climate in the past, it would in the future with higher and higher concentrations. I was just trying to clear that up for myself.

The information I had initially indicated that natural variability was the controlling factor, and if that’s the case then trying to control it ourselves is futile.

I’m always willing to question what I know if I’m given good reason to do that. If this information about carbon dating turns out to be inconsequential, then that’s another idea on the trash heap as far as I’m concerned.

Alan F:

I’m not sure if you were referring to what I said, but I was the one who used the term “believe”, not the person I was talking about. He is quite convinced he has the evidence to back up what he says, though getting him to talk about the evidence has been like pulling teeth.

Mark,

There are two parts in the 14C story: as fossil fuels are completely depleted of 14C (14C is only detectable up to about 60,000 years), the carbon dating after about 1870 was affected. Therefore correction tables needed to be used to correct for the “false” readings, making the carbon date older than in reality.

In the period 1950-1960 a lot of open air nuclear tests were done. This increased the 14C level in the atmosphere substantially. Again new correction tables were needed, now following the rapid increase and more slowly decline of 14C in the atmosphere, due to these tests and the exchange rates with the oceans. The latter show a decline of about 5 years half life time for the residence time of 14C in the atmosphere.

But 14C is not the only “proof” for humans as origin of the increase of CO2 in the atmosphere. The 13C ratio, oxygen depletion, the mass balance, the pCO2 and pH of the oceans, all point to the same origin… See for a comprehensive analysis:
http://www.ferdinand-engelbeen.be/klimaat/co2_measurements.html