tag:blogger.com,1999:blog-16603042.post5490677013413546179..comments2023-03-10T01:20:28.269+13:00Comments on Long Ago and Not True Anyway: I'm not supposed to be blogging but...Terencehttp://www.blogger.com/profile/17321549651265388367noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-16603042.post-8838070649932706952008-04-03T18:40:00.000+13:002008-04-03T18:40:00.000+13:00Thanks Yves,That's a really interesting post. I ac...Thanks Yves,<BR/><BR/>That's a really interesting post. I actually need some time to mull it over. Basically, I think, I take your point though.Terencehttps://www.blogger.com/profile/17321549651265388367noreply@blogger.comtag:blogger.com,1999:blog-16603042.post-31919595622081955082008-04-02T16:14:00.000+13:002008-04-02T16:14:00.000+13:00Hi Terence,About the "CO2 rise is natural" myth, I...Hi Terence,<BR/><BR/>About the "CO2 rise is natural" myth, I retrieved the original stance, quoted from the Oregon petition man:<BR/><BR/>"The concentration of CO2 in Earth’s atmosphere has in creased during the past century. The magnitude of this atmospheric increase is currently about 4 gigatons (Gt C) of carbon per year. Total human industrial CO2 production, primarily from use of coal, oil, and natural gas and the production of cement, is currently about 8 Gt C per year (7,56,57). Humans also exhale about 0.6 Gt C per year, which has been sequestered by plants from at mospheric CO2. Office air concentrations often exceed 1,000 ppm CO2. To put these figures in perspective, it is estimated that the atmosphere contains 780 Gt C; the surface ocean contains 1,000 Gt C; vegetation, soils, and detritus contain 2,000 Gt C; and the intermediate and deep oceans contain 38,000 Gt C, as CO2 or CO2 hydration products. Each year, the surface ocean and atmosphere exchange an estimated 90 Gt C; vegetation and the atmosphere, 100 Gt C; marine biota and the surface ocean, 50 Gt C; and the surface ocean and the intermediate and deep oceans, 40 Gt C. <BR/><BR/>"So great are the magnitudes of these reservoirs, the rates of exchange between them, and the uncertainties of these es timated numbers that the sources of the recent rise in atmospheric CO2 have not been determined with certainty. Atmospheric concentrations of CO2 are reported to have varied widely over geological time, with peaks, according to some estimates, some 20-fold higher than at present and lows at approximately 200 ppm." <BR/><BR/>My opinion: <BR/><BR/>1) AFAIK the numbers in the first paragraph are correct and can be found in any standard carbon cycle diagram, with the exception of the sentence on human respiration (Humans also exhale about 0.6 Gt C per year, which has been sequestered by plants from atmospheric CO2) which is at best misleading. The carbon is not "sequestered by plants" but rather recycled through the biosphere and the human respiration does participate to the mechanism. IMO it is difficult to estimate the net impact of human metabolism because it is integrated in the carbon cycle but may contribute to its alteration via land use change, and as such be a net source of anthro CO2 (see an interesting post from Atmoz dated Dec. 2007),<BR/><BR/>2) The second paragraph smells typical contrarian stance:<BR/><BR/>"So great are the magnitudes of these reservoirs"<BR/>Man, small. Earth, big!<BR/><BR/>"the uncertainties of these estimated numbers"<BR/>Uncertainties, sacred cows. Don't quantify them, rely on our stance: they are huge!<BR/><BR/>"that the sources of the recent rise in atmospheric CO2 have not been determined with certainty"<BR/>Trust us: those taxpayer money fed whackos pretend they know everything, in reality they know nothing!<BR/><BR/>"Atmospheric concentrations of CO2 are reported to have varied widely over geological time, with peaks, according to some estimates, some 20-fold higher than at present and lows at approximately 200 ppm"<BR/>CO2 varied naturally in huge proportions in the past, and puny man definitely can't do it!<BR/><BR/>3) Your comment: <BR/>"Compared to quantities of CO2 to be found naturally in the atmosphere and biosphere, human emission levels are not large. But the important point is that naturally, over a period of broadly stable temperatures, naturally occurring CO2 is in balance. Sources of emission are countered by sources of absorption. The criticical thing here is that we humans are disrupting this balance. That is all that is required to trigger climate change."<BR/><BR/>I think the invocation of "balance" is misleading and rather gives fuel to pseudoskeptic countering like "Balance is the favorite argument of the climate scientology" seen in Coby Beck's blog (How to talk to a climate skeptic, version 1). Indeed CO2 is never exactly in balance and there were variations of atmospheric CO2 levels before the industrial revolution, around +/- 5 ppm during the 2nd millennium (see the ice core data). The problem, the difficulty, is to estimate and compare correctly the imbalances.<BR/><BR/>I would rather use the argument of recycling: the 7 GTC emitted annually have a residence time around 3 years only in the atmosphere but they recycle rapidly through biosphere and surface oceans, which are reservoirs of the same size as the atmosphere (ca 500 GTC for biosphere, 1000 for surface oceans), so that much of the carbon from past anthro emissions is brought back to the atmosphere, contributing to a sizeable part of the gross flux of 210 GTC to/from atmosphere. Therefore, we cannot just make the comparison of that flux to puny man's 7 GTC and conclude to 3% anthro as J. d'Aleo does. This value, though constantly recycled through the denialosphere, is bogus. A good carbon cycle illustration is given in skepticalscience.com (the site of John Cook) under the topic "CO2 rise is natural". OTOH, the oft-cited 50-200 years residence time correspond to the time constants of transfer of the excess carbon to the whole ocean and ocean homogeneisation. AFAIK I recently read of 2 time constants (30 years for most of the excess and ca 300 years for ca 20% of the excess).<BR/><BR/>Nevertheless, note that the above consideration is not a proof that CO2 rise is anthro, only a proof that the oft-cited 3% is false and that the real figure (of anthro contribution of recent rise) is much higher. In order to fully make the case one has to consider the fingerprints of "anthro CO2" source vs "natural" one : the isotope ratios (C13 but also C14, in the atmosphere but also biosphere and oceans), the latitudinal distribution (higher CO2 levels in northern hemisphere), the distribution of the carbon in the oceans (increase of dissolved carbon concentrations, pH decrease, mostly in the upper layers), the historical coincidence of the CO2 rise and of the anthro emissions from land use change + fossil fuels/cements (there is a nice diagram in Stephen Schwartz site), the temporal resolution of ice cores which prove, considering the carbon cycle fluxes, that the CO2 levels are highest for the last 20000 years (the oft-cited 650000 years has a lower level of certainty since the oldest ice cores mix up CO2 on time intervals up to 1500 years, and as such can smooth centennial spikes, and thus cannot disprove levels higher than 300 ppm, which could have occurred in short periods, for instance around the Eemian maximum). <BR/><BR/>So, the anthro case has overwhelming evidence, while the possible existence of a sizeble natural contribution in the recent CO2 rise is at best speculative. I would guess there is one, of a few ppm, because of thermal-induced net CO2 emission (ocean degassing, permafrost melting) due to natural warming since the LIA. But, this contribution might be equal or smaller than ... that from ocean degassing and permafrost melting due to the present "AGW" (positive feedback on the carbon cycle).<BR/><BR/>Hoping having been clear in my explanations.<BR/><BR/>Best<BR/><BR/>YvesAnonymousnoreply@blogger.com