How Much CO2 Emission is Too Much? | ||
AlkalizeForHealth
"The doctor of the future will give no medicine, but will interest his patients in the care of the human frame, in diet and in the cause and prevention of disease." | 6 Nov 2006How much CO2 emission is too much?Filed under:
— david @ 3:18 pm - ( This week, representatives from around the world will gather in Nairobi, Kenya for the latest Conference of Parties (COP) meeting of the Framework Convention of Climate Change (FCCC) which brought us the Kyoto Protocol. The Kyoto Protocol expires in 2012, and the task facing the current delegates is to negotiate a further 5-year extension. This is a gradual, negotiated, no doubt frustrating process. By way of getting our bearings, a reader asks the question, what should the ultimate goal be? How much CO2 emissions cutting would it take to truly avoid "dangerous human interference in the climate system"? On the short term of the next few decades, the line between success and excess can be diagnosed from carbon fluxes on Earth today. Humankind is releasing CO2 at a rate of about 7 Gton C per year from fossil fuel combustion, with a further 2 Gton C per year from deforestation. Because the atmospheric CO2 concentration is higher than normal, the natural world is absorbing CO2 at a rate of about 2 or 2.5 Gton C per year into the land biosphere and into the oceans, for a total of about 5 Gton C per year. The CO2 concentration of the atmosphere is rising because of the 4 Gton C imbalance. If we were to cut emissions by about half, from a total of 9 down to about 4 Gton C per year, the CO2 concentration of the atmosphere would stop rising for awhile. That would be a stunning success, but the emission cuts contemplated by Kyoto were only a small step in this direction. Eventually, the chemistry of the ocean would equilibrate with this new atmospheric pCO2 concentration of about 380 ppm (the current concentration), and its absorption of new CO2 would tail off. Presumably the land biosphere would also inhale its fill and stop absorbing more. How long can we expect to be able to continue our lessened emissions of 4 Gton C per year? The answer can be diagnosed from carbon cycle models. A range of carbon cycle models have been run for longer than the single-century timescale that is the focus of the IPCC and the FCCC negotiation process. The models include an ocean and often a terrestrial biosphere to absorb CO2, and sometimes chemical weathering (dissolution of rocks) on land and deposition of sediments in the ocean. The models tend to predict a maximum atmospheric CO2 inventory of about 50-70% of the total fossil fuel emission slug. Let's call this quantity the peak airborne fraction, and assume it to be 60%. The next piece of the equation is to define "dangerous climate change". This is a bit of a guessing game, but 2°C has been proposed as a reasonable danger limit. This would be decidedly warmer than the Earth has been in millions of years, and warm enough to eventually raise sea level by tens of meters. A warming of 2° C could be accomplished by raising CO2 to 450 ppm and waiting a century or so, assuming a climate sensitivity of 3 °C for doubling CO2, a typical value from models and diagnosed from paleo-data. Of the 450 ppm, 170 ppm would be from fossil fuels (given an original natural pCO2 of 280 ppm). 170 ppm equals 340 Gton C, which divided by the peak airborne fraction of 60% yields a total emission slug of about 570 Gton C. How much is 570 Gton C? We have already released about 300 Gton C, and the business-as-usual scenario projects 1600 Gton C total release by the year 2100. Avoiding dangerous climate change requires very deep cuts in CO2 emissions in the long term, something like 85% of business-as-usual averaged over the coming century. Put it this way and it sounds impossible. Another way to look at it, which doesn't seem quite as intractable, is to say that the 200 Gton C that can still be "safely" emitted is roughly equivalent to the remaining traditional reserves of oil and natural gas. We could burn those until they're gone, but declare an immediate moratorium on coal, and that would be OK, according to our defined danger limit of 2°C. A third perspective is that if we could limit emissions to 5 Gton C per year starting now, we could continue doing that for 250/5 = 50 years. One final note: most of the climate change community, steered by Kyoto and IPCC, limit the scope of their consideration to the year 2100. By setting up the problem in this way, the calculation of a safe CO2 emission goes up by about 40%, because it takes about a century for the climate to fully respond to rising CO2. If CO2 emission continues up to the year 2100, then the warming in the year 2100 would only be about 60% of the "committed warming" from the CO2 concentration in 2100. This calculation seems rather callous, almost sneaky, given the inevitability of warming once the CO2 is released. I suspect that many in the community are not aware of this sneaky implication of restricting our attention to a relatively short time horizon. Note: responding to suggestions in the comments, some of the numbers in the text above have been revised. November 7, 2:31 pm. David
232 Comments1. Can you please provide some indication of the degree of ocean acidity increase that these numbers involve? For example, what pH changes would arise from 500Gt C staying in the air. Have any of the stabilisation studies addressed the impact on marine life? ie. stabilised at 450ppm is a common idea (though that ship may have already sailed), what would that mean for ocean acidification? [Response:I wrote a post on ocean acidification here, but it won't really answer your question about how bad it would be, if pCO2 were stabilized at some level. I guess I feel that ocean acidification is analogous to ozone depletion, in that it seems like a fairly frightening, fundamental change to a component of the Earth system, but it's difficult to point to who exactly would suffer and how much. For ozone depletion, one could get a comparable increase in UV by moving a few hundred kilometers closer to the equator, and yet it seemed a serious enough problem to ban freons, a decision I agree with. Would ocean acidification lead to some sort of biological collapse in the ocean, or extinctions, or would the biological effects even be measurable? It's hard to know. David] Comment by Coby — 6 Nov 2006 @ 3:31 pm 2. RealClimate does an excellent job on reporting the facts about global warming. This piece on co2 emissions is one of the best, realistic, fact driven summary of the current state of affairs.Realclimate should be required reading for every member of the House and Senate.I believe that worldwide co2 emission levels should be immediately reduced by 80%, right now, for us to have any viable chance at reducing the negative impacts of the global warming trends already in the pipeline.The latest conference. in Nairobi, of the parties to the UNFCCC must extend Kyoto beyond 2012 and implement much greater restricions that those currently in effect.Once again, thanks to RealClimate for all the work that you do. Comment by Mark J. Fiore — 6 Nov 2006 @ 3:35 pm 3. Could a 500Gton "emission slug" reasonably called safe given other likely impact besides atmospheric ones the kinds of consequences of ocean acidification that some studies (e.g. The Royal Society, June 2005) point to? Comment by Caspar Henderson — 6 Nov 2006 @ 4:05 pm 4. Given the environmental changes we are already seeing with less than 1C warming, the idea of 2C being "safe" may need some clarification. Is 2C the point at which some irreversible "tipping" points are thought to occur (meridional overturning current disruption; clathrate release; ice-sheet loss; forest die-off; ...)? Putting it another way, can we expect the climate and environment around us to be familiar and reasonably livable still at 2C, for the long term? [Response:Replying at once to this comment and the last (#3). The word "safe" seems a little weird to me in this context also. A smaller CO2 slug would definitely be better. I think Hansen takes 1 degree C as his "safety limit". I guess they're also referred to as "danger limits". Maybe that's a bit better word. And in response to just #4, it's not as clear cut as that to predict when any sort of tipping point might be reached and what it might be that tips. Who knows? We can't even figure out past tips, let alone predict future ones. David] Comment by Andrew Alcorn — 6 Nov 2006 @ 4:23 pm 5. It is silly to say that a rise of up to 2C in global temperatures is not dangerous. A global increase of 2C means will mean an increase of at least 4C on the continents, because they heat much more than the oceans which provide 70% of the surface. Moreover, with polar amplification you will get 8C in mid latitude continental areas such as the USA and Europe, and up 20C in polar regions. That will means a rapid thaw of the Greenland ice sheet, which is already starting to melt, and so the flooding of New York, London, and nearly every other port in the world. Here I am emphasising the effects on the developed nations, not out of chauvism but because there is a myth that it is the developing nations who will suffer and we in the west will get off scot free. It is obvious to me that with a 33% increase in CO2 above preindustrial levels, we have already reached the limit of a safe increase. The scientific commitment to higher temperatures from the one third increase will lead not only to sea levels that will flood our cities, but also to an increased number of hurricanes, drought and floods that we are already seeing. OTOH, the record wild fires that the USA has experienced this year can not continue to increase, since eventually the lack of unburnt forests will set a limit! But unless the scientists come down out of their dreaming spires, join the political debate, and tell the politicians it is time to stop, we will continue to sleep walk towards the precipice, and eventually step over the edge. We do not know the cause of rapid climate change, so we are running forward like a man wearing a blindfolded. What could be more insane than that? When are you scientists going to admit that you do not know all the facts? When are you going to have the courage to admit that you are wrong, and that your hubris has led the world to the brink of disaster? [Response:I apologize, I guess I used the wrong word, as I responded to the last comment. I'm just thinking of a boundary in the continuum of the climate impacts. Greater than 2 degrees C is clearly dangerous, is what I meant to say. Just to have a number, to talk about. The best would be to not change climate at all, I absolutely agree with you. David. ] Comment by Alastair McDonald — 6 Nov 2006 @ 4:39 pm
6.
Some earlier discussion in response to: [Response:The ratio of dissolved CO2 to CO32- is about 1:10 preanthropogenic in tropical surface waters. The two will remain about inversely proportionate as CO2 rises. So double CO2, and you halve CO32-. I'd never thought about this in this way, but it sounds like the ratio of the two would reach 1:1 when CO2 reached about three times preanthropogenic, at which point the buffer is getting pretty weak. We should note that there are huge uncertainties with regard to changes in the circulation and biology of the ocean. David. ] Comment by Hank Roberts — 6 Nov 2006 @ 4:41 pm 7. The Stern report focused on carbon dioxide equivalent, at least the portion I've read, citing current atmospheric levels of GHG of 430 ppm carbon dioxide equivalent and discussing stabilizing at 550 ppm or lower. How would you rewrite this article if the question were, "How much GHG emission is too much?" [Response:I hadn't thought of the other greenhouse gases. Putting them into the mix would definitely make the not-quite-as-dangerous CO2 level go down. I'm not sure we know what methane is going to do in the future (see my other recent scholary work, "Rasslin' swamp gas"). More like to go up than down, though, I expect. David] Comment by Karen Street — 6 Nov 2006 @ 4:51 pm 8. I've heard a few people say that we are really at 420 or 430 ppm CO2 equivalent already, once the increase in other greenhouse gases is taken into account. What is the figure for CO2 equivalent at present or where can I find it? Thanks! [Response:I just calculated an equivalent CO2 of 465 ppm. I assumed a radiative forcing of 3.4 W/m2 for doubling CO2, and that CO2 accounts for 60% of the total greenhouse gas forcing (no aerosols or anything like that). And that the real pCO2 is now 380 ppm. David] [Response: 430 ppm CO2e comes from just taking the 6 Kyoto gases (CO2+CH4+N2O+SF6+HFCs+PFCs). That doesn't include CFCs, nor O3, nor aerosols, nor land use etc. The argument was made in Stern that the uncertainties in the other components don't lead to them being easily incorporated into this definition (which is true), and that CFCs (which are quite well known) are not likely to increase further given the Montreal Protocol and subsequent amendments. Our 'best' estimate of the net effect of all known anthropogenic forcings is around 380ppm (i.e. most everything else apart from CO2 cancels). PS. the most usual estimate for the adjusted forcing due to 2xCO2 is 3.7 (not 3.4) W/m2. - gavin] Comment by Almuth Ernsting — 6 Nov 2006 @ 5:04 pm
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Dang, bad link Comment by Hank Roberts — 6 Nov 2006 @ 5:07 pm 10. Once again it comes down to what the politicians can do in this regard whilst maintaining economic prosperity (seems to be a prerequisite for politicians all over the world apparantly). I still cannot see humankind reducing the CO2 levels by the amount required because we will burn all of the available natural GAS and Oil whilst continuing to burn coal through it all because even if we had an alternatibe to Oil/GAS/Coal it nould take 50 years for a worldwide rollout anyways which will still give us potentially dangerous warming because levels of CO2 burning are going to rise worldwide by 50% by 2040. Its a nasty situation by all accounts. Comment by pete best — 6 Nov 2006 @ 5:20 pm 11. Re #7. How do you get to 465 CO2equivalent exactly? Sorry, I couldn't follow the arithmetic. Its seems an important number many should understand... [Response:Gavin is an atmospheric modeler, I'm a water guy, so I defer on 3.7. For what it's worth here's how I did it. Doublings = ln (380/280) / ln (2) CO2WattsPerM2 = 3.7 * Doublings GHGWattsPerM2 = CO2WattsPerM2 / 60% CO2EquivalentDoublings = GHGWattsPerM2 / 3.7 CO2EquivalentPPM = 280 * 2^(CO2EquivalentDoublings) corrections welcome. David] Comment by Andrew Alcorn — 6 Nov 2006 @ 5:43 pm 12. The problem with emission cuts is that we won't be able to see the science get validated. That would be a real shame. [Response:The Montreal Protocol is a bummer for ocean thermocline tracer types. David] Comment by ninin — 6 Nov 2006 @ 5:58 pm 13. "A warming of 2° C could be accomplished by raising CO2 to 420 ppm and waiting a century or so, assuming a climate sensitivity of 3.5°C for doubling CO2, a typical value from models and diagnosed from paleo-data." Does this warming estimate include the effect of the current earth energy imbalance which means that there is considerable heat stored in the sea which will come out over the coming decades regardless of CO2 concentration in the atmosphere? [Response:Yes, the climate sensitivity parameter is defined as the equilibrium response, after the ocean has had a chance to warm up. David] Comment by Paul Duignan — 6 Nov 2006 @ 6:17 pm 14. I regard Realclimate.org and the work you guys do very highly. However, I feel that this post oversteps the boundaries of what the blog should be about -- communicating and commenting on climate _science_. If we consider improvements in human welfare to be our ultimate goal, judgements on what constitutes a 'dangerous' or 'safe' level of climate change should be based on careful economic analysis, itself ultimately based on a consistent system of values (or a number of alternative value systems, if we find it difficult to agree on a common one). Mitigation of climate change does carry costs, so the question is not trivial! The analysis should, obviously, be as complete as possible, in the sense of considering uncertainties and insuring sufficiently for them, considering potential extreme outcomes, considering the effects the inequal global income distribution has on the analysis, and so on. However, ultimately, the question of what is a 'dangerous' level of climate change is not a scientific question, but an economic and ethical one! I feel Realclimate.org would be stronger for sticking to its chosen mission and recognizing its limitations. Maybe you should encourage a bunch of climate change economists to start a 'twin' blog focusing on the economic / ethical issues? [Response: Well, this post was mainly about what the carbon cycle implies for policy decisions - and that is clearly a scientific issue that those designing such policy need to account for. That is a very different thing than saying that we are in a position to decide what aim policy makers should have or what the cost-benefit analysis shows. David picked some numbers here (I assume) on the 'dangerous' limits because they are prevalent in discussions, not becuase we think that they are necessarily right. Another blog run by RealEconomists would be great though! - gavin] Comment by Niko Jaakkola — 6 Nov 2006 @ 6:39 pm 15. http://www.enviroliteracy.org/article.php/578.html Enjoy. Our young climate scientists not only claim to understand global climate, a very debatable claim, but they also claim to be able to forecast the evolution of technology and the human condition 100 years from now. [Response: Your point being that no efforts to deal with horse-related pollution should have occured because they didn't forsee the motor car? Good one...... -gavin] Comment by joel Hammer — 6 Nov 2006 @ 7:00 pm 16. I would like to point out that some of the figures presented in this article are rather different than those given by James Hansen (eg. in this summary). David says fossil fuel emissions are "5 Gton C per year from fossil fuel combustion, with a further 2 Gton C per year from deforestation," while Hansen states that annual emissions are now 7.5 Gigatons. The 2 Gt/yr for deforestation seems rather high, even if you count forest fires. David says "the natural world is absorbing CO2 at a rate of about 2 Gton C per year into the land biosphere and into the oceans, for a total of about 4 Gton C per year," whereas Hansen says "The ocean is thought to take up about 20-35%, leaving 5-20% as the net sink in vegetation and soil." While a little uncertain, it suggests the ocean takes up quite a bit more than the land. David assumes a climate sensitivity of 3.5 degrees C for doubling CO2, while Hansen works with 2.7 degrees C. Finally, David says "The models tend to predict a maximum atmospheric CO2 inventory of about 50-70% of the total fossil fuel emission slug." Given that about 60% of CO2 is being absorbed now, with little change in trend over the past few decades, what is going to change to reduce that amount substantially? [Response:The range of climate sensitivity from IPCC is 1.5 to 4.5 degrees C. Hansen also assumes 1 degree as a danger limit, if I remember correctly. According to him, we're already over the line (1 degree is the equilibrium warming to the CO2 already in the atmosphere. Sabine et al (Science 305: 367, 2004) estimates that the ocean contains 118 Gton C of the fossil fuel carbon, while the atmosphere contains about 200 Gton excess C. David. ] Comment by Blair Dowden — 6 Nov 2006 @ 7:37 pm 17. Re 14 I think the post actually could have gone much further toward policy without leaving the domain of science - there's an awful lot of science required to determine the impacts of a given level of CO2/warming on the biosphere etc. before getting to the economics. Too many economic impact assessments start with the assumption that welfare=consumption and the global distribution of agriculture and capital is in equilibrium with climate, and neglect the physical world. Comment by Tom Fiddaman — 6 Nov 2006 @ 7:46 pm 18. The figure of reducing CO2 emmisions down to about 10% of current emmisions answers half of a question I've had about AGW. The other half is beyond the scope of this blog, but can anyone point me to a discussion of how much fossil fuel is used for various applications? With current technology any stationary uses of energy can be done with a mix of nuclear, hydroelectric etc., but small mobile machinery like cars, bulldozers & farm tractors are hard to run on anything but fossil fuels. I've seen energy use broken down into categories like transportation etc, but we need more detail to determine how low emmisions can go with current tech, since railways can be electrified & large ships can run on nuclear. Also, any practical cuts would have to be a few % a year continued over decades, as old equipment is replaced with non-fossil or more efficient equipment. How does such a gradual decline in emmisions affect the calculated climate effects? Comment by Jim Baerg — 6 Nov 2006 @ 7:54 pm 19. Conclusion: Acting Under Uncertainty The Montreal Protocol was by no means inevitable. Knowledgeable observers had long believed it would be impossible to achieve. The ozone negotiators confronted formidable political, economic, and psychological obstacles. The dangers of ozone depletion could touch every nation and all life on earth over periods far beyond politicians' normal time horizons. But although the potential consequences were grave, they could neither be measured nor predicted with certitude when the diplomats began their work. In the realm of international relations there will always be resistance to change, and there will always be uncertainties. Faced with global environmental threats, governments may need to act while some major questions remain unresolved. In achieving the Montreal accord, consensus was forged and decisions were made on a balancing of probabilities -- and the risks of waiting for more complete evidence were finally deemed to be too great. "Politics," stated Lord Kennet during ozone debates in the House of Lords, "is the art of taking good decisions on insufficient evidence."14 The success of the Montreal Protocol stands as a beacon of how science can help decision makers to overcome conflicting political and economic interests and reach solutions. The ozone history demonstrates that even in the real world of ambiguity and imperfect knowledge, the international community, with the assistance of science, is capable of undertaking difficult and far-reaching actions for the common good. --------------- http://ozonewatch.gsfc.nasa.gov/
Latest Information Comment by Hank Roberts — 6 Nov 2006 @ 8:13 pm 20. The carbon flux numbers are quite dated. It's now over 8Gt per year from fossil fuels, and rising very fast. See this link for a graph through 2004. http://www.theoildrum.com/uploads/12/fossil_carbon_1850_2004.jpg (that's emissions data from ORNL through 2002, extrapolated by BP fuel production data after that). Global coal production is increasing by 5-7% annually from 2001-2005 (see the numbers at http://www.bp.com/productlanding.do?categoryId=6842&contentId=7021390 It's extremely hard to see how we can stabilize the climate change under 2 deg C on this trajectory, and yet 2 deg C itself seems a dangerously high goal (given Eemian sea level 5m or so higher than present and the present lack of quantitative understanding of how fast the ice sheets will equilibriate to give that sea level). There's also a Science paper this week arguing that maintaining concentration below 450 ppm (which they take to be the threshold for 2 deg C) would require in the near future reaching an annual 3.2% reduction in carbon emissions. http://www.sciencemag.org/cgi/content/summary/314/5800/764 Comment by Stuart Staniford — 6 Nov 2006 @ 8:27 pm 21. Re: Gavin's response to #8. "...most everything else apart from CO2 cancels" ...but, if aerosols are a net negative and given that they have an atmospheric residence time of ~days-weeks compared to ~centuries-millenia for CO2, CFCs, then it's a bit non-useful to cancel out some of the other non-CO2 forcings with aerosols. From a scientific point of view [rather than a political/economic point of view] I'm really worried that the 500-550 ppm CO2-eq stabilisation level takes us far too close to the edge. There are a lot of thresholds at around that ballpark level: Greenland, permafrost melt; soil carbon feedback. It would seem to me that an emissions pathway that took us to 550 ppm, could easily end up being a lot higher [750+?] if we were "unlucky". From a politics/economics point of view, I still don't see any sign of concrete policies being proposed that would limit CO2 emissions at all, let alone stabilise them at any level <1000 ppm. You simply have to look at where the investment money is going [or not going] in terms of the oil majors, etc, to see that the captain hasn't given the order to turn the supertanker around yet. It does seem bizarre that still nothing is really changing on the ground. Comment by Timothy — 6 Nov 2006 @ 8:36 pm
22.
Hello, [Response: It's a neat tactic to package so much mis-information into one article that it requires substantial effort to debunk - effort that most of us can't afford to spend (what with having actual jobs and such). Maybe we need to think about new ways to combine efforts to do this though... WikiDebunk perhaps? But watch this space. -gavin] Comment by Aaron — 6 Nov 2006 @ 8:56 pm 23. Two questions: ... 2C seems a reasonable danger limit. This would be decidedly warmer than the Earth has been in millions of years, and warm enough to eventually raise sea level by tens of meters. (a) I recall that Greenland's ice sheet is 6m sea level rise equivalent, while WAIS is 7m sea level rise equivalent, for a total of 13m. That implies 2C rise is enough to melt GIS, WAIS, and a bit of EAIS. That's a big reduction in surface area covered by ice, and therefor, a big reduction in albedo, right? (Unless it is counterbalanced by more clouds?) ... assuming a climate sensitivity of 3.5C ... (b) Why 3.5C rather than 3.0C ? Comment by llewelly — 6 Nov 2006 @ 9:28 pm 24. I am not a mathemetician or a scientist. I have a layman's question. Assume that some wake up call achieves a revolutionary shift in political priorities re GHG emissions. A year of anarchy perhaps in which gas guzzlers and Beoings are destroyed on the tarmac by an uprising of concerned citizens round the world. Assume that this is enough to make world politicians realise that they should start worrying about their granchildren instead of their own careers. Assume that this year of anarchy occurs in 2008 and as an immediate result GHG emissions were held constant at end 2007 levels through 2008. Following this, the world political community realise that radical global change has to occur in order to return order to the streets. After 2008, by some miracle of honest and fair implementation, global regulation perhaps, that global GHG emissions reduce by 5% per year until end of 2024 (straight line attrition) and that in 2025 fossil fuel use flattens out at 20% of the 2008 level of GHG emissions. Assume that sanctions on the burning of fossil fuels allows innovation to deliver substitute renewable energy sources to sustainably replace all attrition in fossil fuel exploitation. Would this scenario be enough to hold the world temperature increase within the "Stern" 2 degree C target in the longer term? Best Case/Worst Case. Could the GHG emission reduction strategy be less severe than this? Anybody prepared to have a go at this calculation? Phil - A concerned Grandad. [Response:I think to a first approximation you can just add up the total emissions through time of whatever scenario you're envisioning, and if it comes to less than 200 Gton C, you're probably staying within the 2 degrees C. David] Comment by Phil Atack — 6 Nov 2006 @ 9:42 pm 25. RE 21, Timothy wonders why nothing is really being seen on the ground. If there is sufficient ice hung up above sea level to give us say 20 metres of sea level rise, then I wonder if the thing that is holding it all together at the moment is the input of the anthropogenic forcings into the latent heat of fusion being absorbed by all that ice. It's a huge sink. I've noticed that if you put a pair of ice cubes in a box, then they both hold up until they are both ice at zero C, then they both melt with a rush when the trigger Joule is absorbed. If the same thing holds at a global scale, then when it starts to happen we will definitely be living in "interesting times"! I guess a measure of that issue would be the proportion of global ice that is currently at zero C. Do we have any idea of that? Comment by Nigel Williams — 6 Nov 2006 @ 9:43 pm 26. You mention a climate sensitivity of 3.5 C for a doubling of CO2 and say that it's a typical value. I was under the impression (or wishful thinking) that 3.5 C was more towards the high end of the range for climate sensitivity. Are there any estimates of the likelihood of different climate sensitivities? What range for climate sensitivity is the IPCC working on? Thank you. [Response:The range from IPCC was 1.5 - 4.5 degrees C. I don't know if the real climate sensitivity is higher or lower than 3.5 degrees C, I just chose a number for discussion. David. ] Comment by Katherine Cinq-Mars — 6 Nov 2006 @ 10:17 pm
27.
I was wondering if anyone was going to take
on Steven Milloy's latest challenge: He says, "We believe climate models are programmed with excessive climate sensitivity based on a flawed understanding of past ice ages. Moreover, climate models wrongly magnify potential warming to accommodate positive feedback mechanisms while comparison with empirical measure shows negative feedback dominates, reducing warming experienced to about half theoretical values. The challenge is for you to actually check the numbers -- see for yourselves whether we are wrong or not. Look up Stefan's Constant or just use 5.67 x 10-8 (close enough for our purpose but look it up to be sure). Now use it to check the assertion: "Global climate forcing was about 6 1/2 Wm2 less than in the current interglacial period. This forcing maintains a global temperature difference of 5 °C, implying a climate sensitivity of 3/4 ± 1/4 °C per Wm2." Either consult your texts for Earth's temperature in Kelvin and any other numbers you need or see the numbers we've used here. Off you go -- we'll wait. Back so soon -- how did you go, prove us wrong yet? Well, we're waiting. All you need to do is show us where we've messed up the calculations and we'll publicly retract and correct. We've left you plenty of opportunities in our analysis of models and climate sensitivity. While you are about it, see how the "smoking gun for global warming" turned out to be nothing but a clown gun, just another failure of "global warming proof" that didn't make it into mainstream media coverage. Why is that? If it's proving too hard following a moderately complex document, try this simple one where we find significant heating does not trigger self-perpetuating enhanced greenhouse from the most prolific and important greenhouse gas -- water vapor. Same deal -- show us where we're wrong and we'll retract and correct. We believe estimations of "dangerous climate interference" are based on seriously flawed models producing patently ridiculous "projections." We find no evidence the world is conforming to the models and therefore conclude it is the models that are wrong (aren't we terrible?). We see no evidence carbon constraint will have any measurable effect on global temperatures and conclude desperate measures to transform energy supply have vastly greater potential for harm than for good. We place our calculations online where scrutiny is invited and expected. The only question now is whether reporters still follow the science or simply follow the faith." Thank you [Response: He's a funny guy.... We've dealt with the reasons why climate sensitivity is considered to be around 3 deg C for 2xCo2 in many pieces, and Milloy's arithmetical sleight-of-hand doesn't impact any of that. (Clue: dividing any temperature by any energy flux one can get something in the same units as climate sensitivity, but it won't be the same thing). I note that Monckton's recent piece tries to pull the same trick. We may take this on for a bit of target practice.... - gavin] Comment by Christopher Sargent — 6 Nov 2006 @ 10:47 pm 28. RE: David's Post I have a few simple layman's questions. Rather then the data that David lays out we consider the data presented on the Oak Ridge Nat. Lab. that the Global Carbon Cycle Balance on an average year between 1997 and 2002 or even the NOAA data for 2004 we get very different numbers from what I think I read in this article. In the later two examples we have values of between 205 and 210 CT C that goes into the atmosphere and between 207 to 212 that comes out of the atmosphere. Also from these sites we get an average direct anthropogenic contribution to the atmosphere of between 5 and 6.5 GT C where some tables indicate a value as greate as 7.5 GT C (It must be the difference in contribution from deforestation or forest fires). Given this the total anthropogenic contribution to the atmosphere on an annual basis is approximately 3%, if I read things correctly. Though David is likely correct that a reduction of 3-4 GT C would likely allow things to return to a balanced level, it means we must halve the current contribution across the globe to get close to the correct balance. It really does not matter if you recharge your vehicle at the wall socket (Though under nuclear sources this is not true.) or run a methane/ethane/biodiesel converted fossil fuel engine or feed and water your burro your "engine" will still emit high amounts of CO2 with any of these systems. The time necessary to move to a Carbon free energy system is likely a min. of 30 years away. Which is the the preferred manner in which to deal with the problem now? Do you start today to cut back 1/2 of the energy you use every day? Do you only drive 1/2 of the distance to work or school and walk the balance? (I would love to see the average worker in DC drive only 30 miles and attempt to walk the balance in 8 hours there and 8 hours back.) Do you only light or heat your house and warm the water on average for 4 hours every day? (Even with R-40 insulation throughout you would average 1/2 the equilibrium between the daily high and low within 8 hours. What do you do if the high is less then 68 degrees?) Do you not buy anything made of or covered by plastic? Do we reduce the population of the globe by 1/2 in the next 5 years? (Even if you halfed the population of the US you only get back 10% of it's contrabution to GW, that leaves the other 80% to be dealt with.) It simply makes much more sense to boost the natural processes 1.5% to sequester the 3 GT C that it currently is not. Would it not make more sense to start the process of dealing with the immediate problem while working on the other issues. It almost appears that the issues will not get dealt with in a timely manner, so why do we we have to endure the "knawing of the bone" Ad Nauseum. Apparently, if it truly was a big deal you would think a few scientists could put together a fully funded NSF research project that involved a research ship to be chartered to dump several tons of Ironite mixed with sargasso weed for 6 months for less then a million dollars per year. If each of the major industialized countries did the same you would be at a balance in next to no time, wouldn't you? Dave Cooke
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