There is a point at which more CO2 would be just like another set of shutters nailed over several others already blocking light. This point has long been factored in. Mars' atmosphere is thought to have been a lot thicker once. At some point in a pub crawl my mates tend to say 'are we doing one' when they want to move on. Usual notions for Mars' atmosphere 'doing one' are: Possible causes for the depletion of a previously thicker martian atmosphere include the following: Catastrophic collision by a body large enough to blow away a significant percentage of the atmosphere; Gradual erosion of the atmosphere by solar wind; and On-going removal of atmosphere due to electromagnetic field and solar wind interaction. Others suggest its magnetic field 'walked away' - hence that crap move The Core. It's not the CO2 on its own or even in combination with other stuff like methane. On Venus it's held warming isn't greenhouse at all. Indeed, 'greenhouse' is a misnomer - greenhouses heat up by restricting convection. This is the gist:
There is general agreement that the Earth is naturally warmed to some extent by atmospheric gases, principally water vapor, in what is often called a "greenhouse effect". The Earth absorbs enough radiation from the sun to raise its temperature by 0.5 degrees per day, but is theoretically capable of emitting sufficient long-wave radiation to cool itself by 5 times this amount. The Earth maintains its energy balance in part by absorption of the outgoing longwave radiation in the atmosphere, which causes warming (black body and all such jazz). On this basis, it has been estimated that the current level of warming is on the order of 33 degrees C. That is to say, in the absence of so- called greenhouse gases, the Earth would be 33 degrees cooler than it is today, or about 255 K (-0.4° F). There would be little need to keep the voddie in the freezer. Water is by far the most important. Although estimates of the contribution from water vapor vary widely, many sources place it between 90 and 95% of the warming effect, or about 30-31 of the 33 degrees. Carbon dioxide, although present in much lower concentrations than water, absorbs more infrared radiation than water on a per-molecule basis and contributes about 84% of the total non-water greenhouse gas equivalents or about 4.2-8.4% of the total greenhouse gas effect (this is a range bigger than economists often use in their 'highly accurate' predictions). This 33 degree increase in temperature is not caused simply by absorption of radiation by the gases themselves. Much of the 33 degree effect is caused by the Earth's adaptation to higher temperatures, which includes secondary effects such as increased water vapor, cloud formation, and changes in albedo or surface reflectivity caused by melting and aging of snow and ice. Accurately calculating the relative contribution of each of these components presents major difficulties. We aren't guessing, but it's clear there is room for dispute. Infrared radiation comes from two sources: the sun and the earth's surface. CO2 absorbs some of the infrared radiation and re-emits it in a random direction. If there is more CO2, the radiation is absorbed closer to the source. For radiation from the sun, this theory predicts that increased CO2 would cause cooling in the upper atmosphere and warming in the lower atmosphere. Thermometer measurements show that the lower atmosphere was warming between about 1906 and 1944 and between about 1976 and 1998, and either constant or cooling at other times. The validity of the temperature figures is hotly disputed. Traditionally, greenhouse gas levels are presented as dimensionless numbers representing parts per billion (ppb) multiplied by a scaling factor (global warming potential or GWP) that allows their relative efficiency of producing global temperature increases to be compared. For carbon dioxide, this scaling factor is 1.0. The factors for methane and nitrous oxide are 21 and 310, respectively, while sulfur hexafluoride is 23,900 times more effective than carbon dioxide. The GWP from carbon dioxide is primarily due to the position of its absorption bands in the critical longwave infrared region at 2, 3, 5, and 13-17 microns. The increase in the global energy balance caused by greenhouse gases is called "radiative forcing". Geologists tell us that the residence time of CO2 in the atmosphere is on the order of five to ten years. In contrast, the IPCC says it is 50-200 years. Whatever the actual number, there is no question that emitting CO2 will cause it to accumulate over short periods. But other processes, such as sequestration, also work against it, causing the levels to decrease rapidly over time.The arithmetic of absorption of infrared radiation also works to decrease the linearity. Absorption of light follows a logarithmic curve as the amount of absorbing substance increases. It is generally accepted that the concentration of carbon dioxide in the atmosphere is already high enough to absorb almost all the infrared radiation in the main carbon dioxide absorption bands over a distance of only a few km. Thus, even if the atmosphere were heavily laden with carbon dioxide, it would still only cause an incremental increase in the amount of infrared absorption over current levels.Very little of the radiation from the sun at the wavelengths at which carbon dioxide absorbs reaches the surface of the Earth directly. Similarly, very little of the radiation at these wavelengths that originates at the surface makes it all the way to space. Most of the infrared at these wavelengths is produced by black body radiation from objects that have been heated up by absorbing radiation at shorter wavelengths. This means that even if the carbon dioxide levels increase, it will have little effect on the total amount of infrared radiation that is absorbed from the sun. The main effect would be to trap radiation originating at the surface at lower levels in the atmosphere than before, where it would be slightly more difficult for the heat to be re-radiated back into space. This is the principle on which most of the global warming predictions are based.Most of the ultraviolet light (below 0.3 microns) is absorbed by ozone (O3) and oxygen (O2). Carbon dioxide has three large absorption bands in the infrared region at about 2.7, 4.3, and 15 microns. Water has several absorption bands in the infrared, and even has some absorption well into the microwave region. There is already sufficient CO2 in the atmosphere to absorb almost all of the radiation from the sun or from the surface of the earth in the principal CO2 absorption bands. The net effect of all these processes is that doubling carbon dioxide would not double the amount of global warming. In fact, the effect of carbon dioxide is roughly logarithmic. Each time carbon dioxide (or some other greenhouse gas) is doubled, the increase in temperature is the same as the previous increase. The reason for this is that, eventually, all the longwave radiation that can be absorbed has already been absorbed. It would be analogous to putting more and more blankets on your bed -- it soon reaches the point where doubling the number of blankets can't make it any warmer. We may currently be at that point where the current ppms are analogous to one blanket and doubling them would be like adding a second. If we start to sweat, you can bank on someone insisting we don't add any more water vapour to the atmosphere. Pressures on Venus make even absorption comparisons bad science by the way. My guess is that the IPCC has over-stated the case, but this isn't because of the puny amounts of CO2 -these are currently in critical concentrations, in the sense that variations have fairly substantial effects. The future memory may well be that carbon trading was as big a scam as Collateralised Derivative Options. Go forth and grok mate - I'd use stronger language but know we are both shrinking violets and would fade away before the sun gets its chance to fry us to crisps! Beer's Law is part of the calculation (with limitations) - I shall raise a glass tonight to the rest of what you say. On 21 Dec, 18:51, chazwin <[email protected]> wrote: > On Dec 21, 3:49 pm, archytas <[email protected]> wrote: > > > Come on Chaz - most of Mars' atmosphere did one when the magnetic > > field collapsed. > > Er - 'one' what? > The point I was making is that the numpties on the other NGs who > support AGW assume that more CO2 necessarily means more heat, but > there has to be a limit to the amount of heat according to the band > with of the radiation. > After a while more does not mean more. > > Venus, I seem to remember has loads of CO2 and is > > > unpleasantly hot - though not, as I understand because of the CO2. > > CO2 plays a role but there is much more besides, including a range of > acids. > > > There is loads of quantitative research, it's just that the media > > thinks no one can be arsed with any of it. You are conflating a 'tiny > > amount' of CO2 with its trace presence on a scale of vastness you > > don't grok. > > Grok? > > Your point has a compelling logic - when I put it to non- > > > > > > > scientists their heads start to nod. It's reasonable initial > > thinking, but fades when the facts come out. > > The essential argument starts with the properties of CO2 as a > > molecule. Light generally doesn't affect it much, but three > > frequencies of infrared make the molecule bend because it absorbs > > them. All this kind of stuff is known as the result of experiments - > > in my day you'd go to some volume of The Handbook of Physics and > > Chemistry for the data. We can measure the amount of sunlight hitting > > the Earth, know the Earth's size and can apply standard black body > > calculations. These leave a discrepancy between the Earth's > > theoretical temperature and actual measurements, so either black body > > is bolloxs or we look for a model to explain this. This leads to > > greenhouse theory (which in conjunction with orbital forcing brings > > the sums back in order. Small experiments done by other than BBC > > patronising goons give the basic figures which can them be expanded > > into the estimates of total greenhouse gases, of which CO2 is a minor > > but substantial part. The models are quite complicated and have to > > take collisions between molecules into account. The sums are > > basically what the IPCC has put out. Most people are simply so poor > > at science they can't get this far. > > The models may be wrong. Orbital forcing, for instance, is thought to > > vary the amount of sunlight hitting certain latitudes by as much as > > 25% (hence the ice ages), which is obviously big in comparison with > > CO2 effects, though the amplification model of greenhouse warming may > > be enough to prevent the 'next' ice age. > > Let's hope so. The models bouncing around in the mid 1970s resulted in > a bif ice-age scare. I imagine you are old enough to remember it. > WIth a background in archaeology I know only too well that we are > currently in an interstadial and the next ice-age is fast becoming a > little overdue. > > > The role of CO2 in this is > > marginal, but marginal effects often amplify. 96% of sweet FA is, of > > course, much more marginal than parts per million in a lot. Spark > > plugs are a negligible weight in my car, but the sod won't run without > > them. > > Not a very good analogy, you might as well have mentioned the > cigarette lighters. > > > > > There is a wider point similar to yours as to whether the marginal > > effects are enough given the percentage variations in the models, but > > this really starts in quantitative review and qualitative questions as > > to whether the models are right even in the sense of being approximate > > enough. Somewhere in this Chaz, is something like me trying to teach > > the electro-chemistry of rusting to 12 years old who don't know what > > iron is (one classic answer because I'd just done something explosive > > with magnesium to wake them up, was that rusting happens because of > > the magnesium - you must have had similar classics in your own > > teaching). > > I still get the feeling that the world and the necessary factors that > contribute to this issue are still beyond the ability of scientists > and their models. Coupled with the will to succeed and the necessity > to continue keep getting the grants, tends to press a certain > direction for assumptions upon which models are designed. > GW seems to be the new Kuhnian paradigm and I can't help but think > that the next generation will look back in amusement as we do with > eugenics, social Darwinism and phogistan. Or they could be fried to a > crisp! > > > > > > > Sue and I started a conversation to establish what we really knew > > about 'global warming' and the answer was pretty alarming and not far > > off sweet FA. We found a few papers and a book, had a bit of a read, > > noticing we were excluding the vast majority of Internet bull. Our > > conclusion so far is that the real arguments are still in the margins > > of a load of hot air. We didn't find reason to doubt the CO2 basics > > though - it lets sunlight in because it doesn't absorb those > > frequencies, but does absorb the bounce back infrared and this is > > retained in a complex collision network and stays in part of the > > atmosphere. This is a confirmation of basic science. The models hang > > together and the sums work. The questions are not about basic CO2 > > absorption, but there are questions about the complex models of > > exchange and balances. One would hope these scientific arguments are > > defeasible, subject to change on new facts and new models. Many > > papers are, in fact, of the 'you left this out' or 'what if' kind. > > They themselves have to be subject to being bagged-off. I'm afraid > > this is the fate of your initially interesting conjectures, a bit like > > the creationist asking 'where are the transition fossils then, evil > > atheist bastard?' > > Oddly I was called a 'creationist' for doubting the CO2 science! But > then I do not expect any sense from a person that did not really > understand my question. > > - the answer being 'over there, have a look'. You > > > > > just don't know enough here. What's really interesting is that the > > case hasn't been made properly and concisely even for people like us. > > Answers to your question start with getting to grips with black body > > radiation, the sums of that and then looking about in basic science > > for reasons to change the sums to retain the basic science - this > > information is widely available, both in qualitative modelling and as > > the spreadsheet sums. > > > On 21 Dec, 10:50, chazwin <[email protected]> wrote: > > > > All the stuff that is out there point to CO2 as a GHG, but none of it > > > has quantitative information. > > > What worries me is the tiny amount of CO2, what the limits are due to > > > the narrowness of the radiation spectrum it can absorb, is CO2 able to > > > change the properties of the air as a whole or does the temperature > > > change rely on its concentration. > > > There seems to be an implication that CO2 prevents heat leaving. Would > > > Mars not be hotter with nearly 96% CO2? There has to be limits. > > > > On Dec 21, 1:41 am, archytas <[email protected]> wrote: > > > > > The work on this is not new - a Swede called Arenheus (spelling) did > > > > the work around 1900. This from Wiki: > > > > Arrhenius developed a theory to explain the ice ages, and first > > > > speculated that changes in the levels of carbon dioxide in the > > > > atmosphere could substantially alter the surface temperature through > > > > the greenhouse effect.[3] He was influenced by the work of others, > > > > including Joseph Fourier. Arrhenius used the infrared observations of > > > > the moon by Frank Washington Very and Samuel Pierpont Langley at the > > > > Allegheny Observatory in Pittsburgh to calculate the absorption of CO2 > > > > and water vapour. Using 'Stefan's law' (better known as the Stefan > > > > Boltzmann law), he formulated his greenhouse law. In its original > > > > form, Arrhenius' greenhouse law reads as follows: > > > > if the quantity of carbonic acid increases in geometric progression, > > > > the augmentation of the temperature will increase nearly in arithmetic > > > > progression. > > > > This simplified expression is still used today: > > > > ÄF = á ln(C/C0) > > > > Don't mistake any of this with 'greenhouse science' - it's basic > > > > physics and chemistry and works at the bench in every experiment we do > > > > in stuff like how much heat comes out if we lob a sliver of magnesium > > > > in an acid etc. - stuff you will have done - and in stuff like > > > > creating Bose-Einstein Condensates in which to trap light as matter > > > > (Lene Hau). You should grok after a trip to Wiki. This question is > > > > at the level of trying to get 12 year olds into a chemical explanation > > > > of how rusting takes place, not at all easy as scientific > > > > understanding is as rare as rocking horse droppings. > > > > > On 21 Dec, 00:57, archytas <[email protected]> wrote: > > > > > > I'd start at New Scientist Chaz. > > > > > > On 20 Dec, 10:44, chazwin <[email protected]> wrote: > > > > > > > I have searched in vain for any evidence that CO2 is a significant > > > > > > greenhouse gas. > > > > > > According to radiometric dating of Carbon isotopes it is thought the > > > > > > the amount of CO2 has increased from 0.028% - 0,038% in the last 100 > > > > > > years. > > > > > > Unless Carbon has some magical properties is seems unlikely that > > > > > > such > > > > > > tiny concentrations should cause any significant increase in > > > > > > temperature, even-though it is a greenhouse gas. > > > > > > Can any one help me find the scientific evidence? > > > > > > I don't want to the political answer, nor the circumstantial answer, > > > > > > nor any sceptic/denier/doubter information as I have heard it all. > > > > > > What I want is the basic physical science of carbon that suggests > > > > > > that > > > > > > a 0,01% increase can be held responsible for a proposed 1 degree > > > > > > increase in temperature. -- You received this message because you are subscribed to the Google Groups "Epistemology" group. 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