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How much CO2 emission is too much?

Filed under: — david @ 6 November 2006 - (Slovenčina)

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 Responses to “How much CO2 emission is too much?”

  1. 51
    Tom Fiddaman says:

    Re original, 36, 48, 50 etc.

    The last common data point in the Marland and Houghton datasets I linked in 37 above was year 2000, with 7.3GtC fossil/cement and 2.1GtC land use for a total of 9.4GtC emissions. Mauna Loa CO2 jumps around a bit, but if you average a few years of data +/- from 2000 using 2.13 GtC/ppm, the net increase is around 4GtC which puts uptake at about 5GtC or about 60% of emissions. I’d guess that the majority of that 5GtC is rapidly mixing into the surface ocean, with a smaller portion taken up by biomass or transported into the deep ocean.

    [Response:Thanks all for correcting my sorely out-of-date emission figures. This summary looks good, except that the ocean is only taking up 2 or 2.5 Gton C per year, the rest seems to be going into the high-latitude terrestrial biosphere someplace. The part I’m still having trouble with, which made more sense with my older numbers, is the airborne fraction, which Hansen in this summary cited above shows as consistently 60%. In any event, the bottom line conclusion is that cuts of more-or-less 50% (maybe 60% according to Hansen) would be required to stabilize atmospheric CO2. David]

  2. 52
    Hank Roberts says:

    Well, apparently the fishing industry is doing its own iron fertilization experiment — perhaps we’ll see which of the many organisms benefits most and whether this causes the problems the plankton experts have been worrying about.

    Found here:

    —– excerpt follows ——-

    “… Already commercial outfits are dropping iron filings overboard, hoping to increase fisheries – meanwhile claiming they are helping to prevent global warming.”

    In fact, Bishop explains, “if the excess fixed carbon in plants is eaten by fish near the ocean surface, the net effect is no gain. And in every part of the ocean there are open mouths.”

    No one really knows where the carbon trapped by fertilization ends up. In one iron-fertilization experiment in warm equatorial waters, chlorophyll increased 30-fold in a week, and there was increased carbon sedimentation down through 100 meters. But the bloom shortly dissipated, the fate of the carbon in deeper waters wasn’t followed, and long-term effects weren’t measured.

    In a more recent experiment in cold Antarctic Ocean waters the plankton bloom persisted much longer. Seven weeks after the experiment ended a distinct pattern of iron-fertilized plankton was still visible from space – “which means the fixed carbon was still at the surface.”

    Bishop says that “people who want to add iron think the particulate matter will fall straight to the bottom; I have sampled natural plankton blooms, and I have not seen that happen…..”

  3. 53
    Tom Fiddaman says:

    Re 51 (David’s comment)

    Comparing Hansen’s charts 4 and 5, it looks like he’s including only fossil emissions in the airbrone fraction calculation. 4GtC/yr atmospheric increase divided by 7.3GtC/yr fossil/cement emissions equals about 55% – consistent with Hansen’s 58% long run average. Neglecting land use emissions in the calculation of the AF seems a bit odd, but it’s consistently done that way in my experience. As you say, the bottom line is about right either way.

  4. 54
    Karan says:

    Great articles on this site…Thank you for them all. One request I would make is to do an article that analyzes the front page of and highlights the errors/misconceptions (I’m pretty sure there are, unfortunately I cannot tell what they are because of my lack of background on the subject).

  5. 55
    Hank Roberts says:

    Karan, use the Search box, it will find what you’re asking for.
    For example:

  6. 56

    I have enjoyed this blog very much. But the papers I have been reading recently eg ( seem to make it clear that there is no proven causal link between CO2 and temperature in the paleoclimate data. Why do we assume that the present warming ( which does seem to be a fact ) is caused by our CO2 emissions?

    [Response: We don’t “assume” it; nor is it to be proven from the palaeo data. There is a good theory to say that increasing CO2 should cause warming; simple and complex models built from the theory demonstrate this. Although the lags complicate things, there is no current way to explain the glacial/interglacial temperature changes without including CO2 feedback -William]

  7. 57
    James says:

    Re #36: You say “My point is that technological innovation is still going on. Projecting our current technology 100 years into the future is just not realistic.”

    Which is true enough. The point you seem to have missed is that not much technical innovation is needed, since the technology needed to significantly reduce CO2 emissions already exists, and could be brought on line economically. The problem, if I may continue your horse manure analogy, is that the horse breeders and hay dealers have managed to convince the public that their status depends on owning the biggest pair of Percherons or Clydesdales on the block :-)

  8. 58
    Richard LaRosa says:

    Re:33,38. I just want to emphasize that present GHG concentrations influence the present rate of temperature rise. I don’t think most people understand this simple point. I’m only talking about the present slope of the temperature vs. time plot. It predicts temperature in the near future. Understand, savor, enjoy this simple fact before attempting to predict further into the future.

  9. 59
    Bryan Sralla says:

    Gavin, you said: “the reason horses were phased out as quickly as they were was because the costs associated with using horses (maunre, dead carcasses, stabling etc.) were bourne by the same entities that benefited from their services (i.e. cities and businesses).” and “If you want to take a lesson from that, it is that the costs associated with GHG emissions should be bourne by the producers of those emissions such that no new technology is handicapped by effective subsidies to fossil fuel users.”

    Your history lesson on horses is new to me. I am also curious which technology you believe is handicapped by subsidies to fossil fuel users? To which subsidy are you referring? Are you saying that the producers are selling the consumers their product too cheaply (passing on some kind of hidden subsidy so consumers will keep using their product)? I will have to say that your complete comment is lost on me.

    [Response: This is normally discussed using the term ‘externalities’ and often comes up in environmental discussions. If a factory makes a product that creates waste, and that waste is simply thrown into the river, then the communities downstream are affected. If they have to pay to clean it up, that cost is not bourne by the polluters and is not reflected in the price of the widget the factory makes – the costs of pollution are ‘externalised’ in the budget of the factory. If the factory was made to clean up the waste ahead of time, that cost would be reflected in the price of the widget – it would be internalised and thus figure more prominently in discussions over whether the widget was good value for money. This is a reasonably easy case since most effects are local/regional and so laws and regulations can be easily enacted to internalise most of the pollution-related costs. The same was true for horses. The greenhouse gas situation is very different since the costs of GHG emissions are likely to fall on communities that have no connection to the source of the pollution. For the sake of argument, let’s assume that GHGs increase sufficiently to melt a big chunk of Greenland. The people who will end up with all the costs are people in low-lying coastal areas like millions of Bangladeshis – hardly the world worst polluters. If the costs associated with flooding Bangladesh were internalised, then the cost of emitting CO2 would be higher and a fair comparison between different sources of energy (each with their own internalised costs) could be made. However, that clearly isn’t the situation we have, and so we effectively have future Bangladeshis (or whoever) subsidising our use of fossil fuels. Compared to alternatives (solar, hydro etc.) that makes fossil fuels artificially cheap – and thus harder to dislodge as a dominant energy source. The market solved the horse manure problem because it was cost-effective to do so, the market failure (no one is including the costs in the price) for the case of GHG emissions makes it very difficult for the same thing to happen now. – gavin]

  10. 60
    yartrebo says:

    An analogy I like to use is that of the Titanic. If you see an iceberg up ahead, do you convene your engineers to debate the effects of ice hitting a ship or do you have the engine room throw the engines in reverse and turn the ship as hard as it will go?

    The way we’re handling our planet is akin to a captain saying “Convene the engineers to debate about the ice, but I’m going to plow through that iceberg anyway. After all, this ship is unsinkable and turning would waste precious time and coal.”

  11. 61
    Bryan Sralla says:

    Re: Yartrebo, The iceburg has already been struck. We did not see it in time. It is now probably a good idea to get a damage control report, and see if we are taking on water. If in fact we are, we need those engineers to decide if 1) all the compartments will flood and we will sink (no lifeboats!) 2) only one compartment will flood, the ship will list a little, but we can make it back to port, 3) the ship is leaking but the bilge pump capacity is large enough to continue on to our destination without many problems, or 4)we need to go down there and try to fix the leak, or we will surely sink.

  12. 62
    Timothy says:

    Re: 58 – There is the beginnings of some interesting work on decadal climate predictions.

    This combines information about the present state of the oceans and their dynamics, with the GHG forcing, etc.

    I hear that the present forecast is for global mean temperatures to be slightly below the trend line for a few years, but that half the years after 2009 will be warmer than 1998.

    The point is that although the GHG forcing will determine the energy imbalance over the period as a whole, internal dynamical forcing will have a very strong influence on the short timescales that are also important for people [as opposed to simply looking at the system as an interesting experiment]

  13. 63
    Steve Reynolds says:

    Re: Gavin’s comment on 59:

    That is a very good point, but at least for gasoline, even in the US, just the federal tax amounts to about $12/tC. That is very close to the $14/tC (median peer reviewed) published value for the marginal societal cost of disposing of CO2 in the atmosphere. Add in state taxes, and there is no subsidy.

    Coal is probably a different story, however.

  14. 64
    Ron R. says:

    Way off topic but I’m just wondering if this November is a bit anomalous. At 3:00 pm my thermometer, in the shade mind you, hit 92 degrees F. The date is 11/7/06.

  15. 65
    Nigel Williams says:

    Re #45 re #25 Hi Yartebo!

    The Ice at zero C Im talking about is ice that has absorbed all its required latent heat of fusion (which it does while hovering at zero C), and whose next move is to change from ice to water. My *trigger Joule* is the last bit of energy needed to unbond the ice molecules from solid to liquid.

    Broadly, the point Im making is that the existing ice mass is a huge energy sink, which will be tending to absorb LHoF in a fairly uniform manner over the globe. Once that sink is near fully utilised then we will see global temperatures rise as they would in the absence of such a sink (markedly more rapidly) and the ice mass converting to water much more rapidly than the few drips we are seeing now.

  16. 66
    Ron R. says:

    I guess it would help if I told you where I am. Central California, just inland a bit (other side of the Las Padres mountains). The coast usually has mild seasons but on this side we tend to have more defined seasons. I just don’t recall November being this hot, and it’s been like his all week.

  17. 67
    Hank Roberts says:

    Ron, the historical information you want is available here:

    I don’t know when they started charging money to see it. Funny.

  18. 68
    Paul Duignan says:

    Re #62, Timothy, do you have a url to any of that work. Thanks.

  19. 69
    James Annan says:

    Re 34, 35, 37, 39:

    Even if one assumes the premise that we are “optimally adapted” to the present climate (which I think would be difficult to rationally defend), it does not follow that changes to the climate would result in net costs.

    In fact, our adaptation to the current climate (eg in agriculture and infrastructure, as have been mentioned) is also a matter of economics, technology and politics, and we can guarantee that these will continue to change at quite a rate.

    Of course we can all agree that a drought in an area that is already somewhat short of water is a bad thing that will likely cost money, compared to exactly the same situation without the extra drought. However, an increase in rainfall in such an area is likely to be beneficial (so long as it is not excessive and leads to flooding), even if society is well adapted to the status quo. The opening of the Northwest Passage is likely to bring significant economic benefits by reducing transport costs, even though (of course) we are currently adapted to its impassability. Warmer winters will reduce the winter death rate in the UK for sure, and this vastly outweighs any plausible estimate of heatwave deaths, at least for a range of modest warmings, even before we start to consider any adaptation to the summer heat. We could of course achieve a similar effect by insulating homes and reducing poverty, of course, but we are already “optimally adapted”, right?

    To boldly assert as axiomatic that “change = bad” is, I think, rather naive and simplistic. All sorts of (social, economic, technological) changes are inevitable, and the latter two at least have a strong record of bringing substantial (no, massive) benefits. Would anyone be silly enough to argue that these changes are bad because we are adapted to the status quo? While I am sure that some climate changes will increase pressure on some ecosystems and human societies, it seems to me to be a rather more nuanced situation than some of the comments above would indicate. Indeed, if the climate changes are slow and modest enough compared to the other changes, it might be hard to detect their overall effect at all (on human health, wealth and happiness, I mean – of course I’m sure it will be easy to measure environmental parameters that document the climate change itself, indeed this is already clear enough). I’m sure UK residents will have noticed the substantial northward march of maize as a crop in recent years (for cattle fodder). I’m not sure to what extent this is due to politics (subsidies), economics, climate change, breeding of better-adapted varieties, or even just farmers gradually realising that it grows better than they had thought possible. Even if climate change is the largest factor (which I doubt, but it’s possible), it is not clear who lost out here, other than perhaps the bugs that prefer to live on kale (or whatever the displaced crop was).

    Living as I do in a country where houses are expected to last about 30 years, I find it hard to take seriously any worry that they might not be optimally adapted to the climate 100 years hence (let alone the sea level a few centuries later). Note also that a change in fuel prices would change the optimal amount of insulation irrespective of climate change. Likewise, advances in building materials will likely render current designs somewhat redundant.

    Extropians would assert that “change = good” and that we should encourage change unless it is proven harmful. Just to be clear on this, I do not endorse this point of view 100% but the difference in opinion seems as much philosophical as scientific. I think that understanding this POV goes a long way to explaining the differences between the environmentalists and the sceptics (even if it does not excuse the dishonesty of the denialist wing).

    I hope this doesn’t sound too much like a septic handwave, expecting techology to magically save the day. To the extent that climate change is rapid or substantial (which I will deliberately leave undefined here!), of course it’s a threat that should be taken seriously. It is a little scary to think about how dominant the human influence can be, and perhaps a mental model of some hypothetical stasis is a comforting thought in which to ground our personal philosophies. But it would be a mistake to let one’s comfort zone unduly colour one’s perceptions of reality (or at least, such effects need to be openly considered and one should be prepared to see them challenged).

  20. 70
    Tom Fiddaman says:

    Re 63

    I think $14/tonC is a bit low for the median (what papers were included in the calculation?). It’s probably not too far off though. However, the models that draw such conclusions make assumptions varying from the unethical (the welfare of future generations is less important than ours, and the welfare of poor people is less important than the welfare of rich people) to the ridiculous (the earth doesn’t conserve carbon, carbon intensity of the economy can be adjusted overnight, people know the future, and – my favorite – the economy will stop growing of its own accord over the next century or two). If you make more sensible assumptions, the value is in excess of $150/tonC, and in some cases much higher. And that’s not even accounting for other externalities associated with fossil fuel use, nor for the possibility of institutional or cognitive failures that make negative-cost reductions a possibility. Even if you entirely neglect climate and other externalities, the OECD surveyed energy prices a few years ago and found frequent net subsidies.

  21. 71
    yartrebo says:

    Re #65:

    Ice melts in a single step. It doesn’t store 80 kcal/kg of energy (latent heat of fusion) and then suddenly melt when the next joule is added. Instead, ice melting can be thought of as an endothermic chemical reaction that is in equilibrium. Each water molecule absorbs about .06 eV in the reaction. Either the water molecule is tightly bound in a crystal lattice with 0 eV potential energy, or it is loosly bound as a liquid with +.06 eV potential energy. There is no in between state.

    What happens is that each time you add .06 eV to the ice at 0C, one molecule of solid H2O becomes a molecule of liquid H2O. If you add 80 kcal of heat to ice, you’ll melt 1 liter of the ice, and the rest will remain just as solid as ever. Each time you add 80 kcal you’ll get another liter, until there is no more ice left.

    PS: State changes are pretty well covered in high school chemistry. Perhaps a beginner’s chemistry textbook would explain it much better than I ever could.

  22. 72
    Onar Ã?m says:


    while your calculation is interesting it is wrong to say that it is based on the facts. It is based on models, and that is not the same thing.

    Furthermore, there is an issue here that is completely missed, namely the element of time. 2 C warming could be dangerous, but when? When will this eventually lead to several meters of sea level rise? If the answer is, as I suspect, at the very minimum 60-80 years into the future, then consider the following very simply reasoning:

    the fuel of all economic growth in the West is productivity growth. People think of this as simply more money, but it is not. Translated into physical action it means the ability to do more with the same amount of work. There is plenty of reason that productivity growth due to innovation will steadily rise by some 4-5% per year in a business as usual model. What does that translate into in, say, 50 years? Historically a 10-doubling in productivity. What that means is that by simply going about our business as usual we will be able to get 10 times more work done per capita in 50 years than today. Think about what that means for a second. It means that mitigation that would cost a whopping 400 billion dollars per year today would cost only 40 billion dollars per year in 50 years. It also means that any damage inflicted by climate change (e.g. hurricanes etc.) would cost 10 times less to deal with.

    Finally, since climate experts are not population, political and economic experts they tend not to know the relationship between these. Allow me to illuminate: rapid economic growth NOW in the third world countries makes them complete the demographic transition faster. Translated into mundane English: the more rapid economic growth NOW, the less people to emit CO2 (and other gases) in 2050. In short, rapid economic growth is a mitigation strategy. The difference between rapid growth and low growth could be the difference between 9-10 billion people in the world and 15-20 billion people. Thus, rapid economic growth could lead to a long term reduction in carbon emissions per capita of over 50%.

    In light of this I think advocating any curbing of economic growth today is illfounded to put it mildly.

    [Response:Many environmental problems are solved by prosperity, but CO2 emission is not one of them. Rich people on Earth emit far more CO2 than poor people do. David]

  23. 73
    Steve Reynolds says:

    Re 70:>I think $14/tonC is a bit low for the median (what papers were included in the calculation?).

    Here is my source (looks at 28 published studies):

    Energy Policy 33 (2005) 2064â??2074
    The marginal damage costs of carbon dioxide emissions:an
    assessment of the uncertainties
    Richard S.J. Tol

    One hundred and three estimates of the marginal damage costs of carbon dioxide emissions were gathered from 28 published studies and combined to form a probability density function. The uncertainty is strongly right-skewed.

    If all studies are combined, the mode is $2/tC, the median $14/tC, the mean $93/tC, and the 95 percentile $350/tC. Studies with a lower discount rate have higher estimates and much greater uncertainties. Similarly, studies that use equity weighing, have higher estimates and larger uncertainties. Interestingly, studies that are peer-reviewed have lower estimates and smaller uncertainties. Using standard assumptions about discounting and aggregation, the marginal damage costs of carbon dioxide emissions are unlikely to exceed $50/tC, and probably much smaller.

  24. 74
    Lynn Vincentnathan says:

    RE #59 & subsidies to oil, from what I understand (I asked my rep) there are actual subsidies & tax breaks to oil (avoidance of externalities aside), and if you throw in the costs of wars and military protection for our oil supplies, and all other gov helps,…well, we’re paying through the nose April 15th for other people’s gas-guzzling. Not to mention paying an increasing price for GW harms in our insurance bills & tax & repairs.

    So, I’d be happy with a level playing field for alt energy, & ecstatic if it got more subsidies/breaks than oil. And I’d prob faint with disbelief if costs of external harms now & in the future were added in to the price at the pump. I guess we’d be paying the real cost of gas, maybe $30 a gallon or more (which is only fair – you break it, you buy it). That’d make people a lot more creative in coming up w/ solutions & implementing solutions already available.

  25. 75
    Hank Roberts says:

    Nigel, you wrote:
    >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.

    Could you try that again and report back on what you see this time? Using a transparent box, not an opaque one?

    I’m thinking that you have ice made by filling a container and freezing it solid, then taking the box out and watching it. If so, and if the air is dry, it can look superficially like you describe.

    Here’s my guess — what happens is you get, first, freezing from the outside in; you may not even have frozen all the water, some may be still liquid at the center. If it freezes solid it will dome up or you’ll get something like hoarfrost.

    When you take the container out, the ice starts melting from the outside as the container surface warms up, and at the same time — in dry air — you can be getting enough evaporation off the top of the ice where it’s exposed that it stays colder longer than the rest of the block — so you end up with a skim of ice on top of a box of water. That might appear to be what you’ve described.

  26. 76
    Colin KLINE says:

    Colin KLINE (Engineer, ret.)
    08 November 2006

    Could learned contributors help me by critiquing this (draft) paper of mine.

    In the current debate about Greenhouse Effect, Climate Change, Energy Crisis, etc, there is in many minds a lack of clarity about these environmental issues, and the urgency of resolving them. This is not helped by certain agencies employing a substantial budget to spin disinformation about these topics. A catalog of this disinformation propaganda, the agencies, the people involved, and the huge funds employed, can be viewed at:

    There are nevertheless many people of good will who are investigating Measures of Energy Technologies, but are still locked into a methodology of old. This is the familiar analysis of costs and efficiencies in terms of: dollars, $ per capita, $ per kgm of fuel, $ per Joule of heat released, Joules released per kgm of fuel consumed, $ per kgm of carbon released, amortised maintenance and staffing $ per lifetime of plant, energy reticulation $ costs, network capacity factors, etc. The energy candidates currently undergoing this analysis are: coal, petrol, diesel, bio-fuels, wind, solar, tidal, geothermal, nuclear, metal-fuels.

    But first, an analogy, however imperfect. If a relative, or someone near and dear, is critically ill, the majority of us would, if necessary, “hock our homes” in order to fund their treatment and cure. If the patient was suffering a high fever, we would request immediate treatment, rather than wait to “see if the patient dies”.

    Observe now that a very dear “relative”, Planet Earth, is by many reputable accounts, now suffering a mighty fever. For example, consult New Scientist, 27 September 06, which contains a report titled “Climate Change: One Degree And We’re Done For”. There are cited in this article five “environmental experts”, and seven authoritative scientific bodies, who express great concern.

    Now what is needed is a new methodology for assessing Measures of Climate Change, i.e., what is the best measure of the “tipping point”? One measure is if the Atlantic Gulf Stream reverses Another is when the Boreal Forests (southern part of the Taiga biome) thaw

    The latter event would release stupendous amounts of CH4 and CO2, dwarfing anything that man or nature currently creates. According to this urgent view, mankind could take every car & truck off the road, ground all jetliners, close all coal fired plants, replace every light bulb with a high efficiency bulb, construct 1000 Nuclear Plants, and all would amount to aught in the face of this polar gas release.

    Another (“doomsday”) view, is that there is already too much greenhouse gas(es) in the biosphere to be able to reverse any effective change for the better. In this view, it is postulated that none of the above Energy Technology candidates will “get there in time”, no matter how hard we try.

    What concerns many are these questions: Is there an authoritative date estimate for when this tipping point might occur? What would be the best measure of the rate of deaths, human, animal, plant, that would ensue after such a catastrophe? These new measures are the ones that should apply, not a concern for dollars and efficiencies of the “cure”. The dollar cost of climate catastrophe will far outweigh the savings of doing nothing, or time-wasting penny-pinching about other useless solutions.

    Luckily there is a ‘quick’ solution that could ‘save our bacon’, namely ‘Space Mirrors’. In this idea, the main focus is on planetary warming – forget CH4 and CO2 for the moment – they are just agents that exacerbate heating. The principal agent of warming is the influx of solar radiation, in particular the Infra-Red end of the light spectrum. The solution thus is to place several ‘sun umbrellas’ out in space, to proportionally shield the Earth, by reflecting the excess of incoming IR radiation (back into space). One cannot argue that this would ‘starve’ the planet of IR radiation – the greenhouse effect is testament that we already have too much of it – in fact we need to block any further excess IR from the sun entering our biosphere. This solution is the ‘bullet-in-the-breech’ insurance needed just in case change is rapid.

    Such parasols would be constructed from thin plastic film, embedded with nano-wires, or made of polymer dielectrics, reflecting only IR, but passing visible light & UV. They would have low mass, use automatically unfurling sails, be located at several libration points in space, and thus would perpetually track the Earth in its path around the Sun, whilst always shading Earth – The choice of IR reflection would ensure the biosphere on this planet would be minimally affected. Even better, if the shading mainly focused on the polar regions, it would stabilise the Boreal Forests. Or, just the polar regions could benefit by shading from total light spectrum, by a ‘super-mirror’ The rate of cooling can be easily controlled by tilting these parasols. Use of attached ion thruster engines can steer and locate the parasols, and would have an excellent life-thrust performance.

    But alas, there exist too many climate change skeptics ruling the major countries needed to mount this solution. So a ‘deal-breaker’ strategy could be for concerned citizens to take over and launch the parasols themselves. A citizens’ global disaster fund could then hire missile technologies from India, or China, to launch these parasols for mankind.

  27. 77
    Hank Roberts says:

    “We are writing … as U.S. Senators concerned about the credibility of the United States in the international community, and as Americans concerned that one of our most prestigious corporations has done much in the past to adversely affect that credibility. We are convinced that ExxonMobil’s longstanding support of a small cadre of global climate change skeptics, and those skeptics’ access to and influence on government policymakers, have made it increasingly difficult for the United States to demonstrate the moral clarity it needs across all facets of its diplomacy….

    “A study to be released in November by an American scientific group will expose ExxonMobil as the primary funder of no fewer than 29 climate change denial front groups in 2004 alone. Besides a shared goal, these groups often featured common staffs and board members. The study will estimate that ExxonMobil has spent more than $19 million since the late 1990s on a strategy of “information laundering,” or enabling a small number of professional skeptics working through scientific-sounding organizations to funnel their viewpoints through non-peer-reviewed websites such as Tech Central Station. The Internet has provided ExxonMobil the means to wreak its havoc on U.S. credibility, while avoiding the rigors of refereed journals. While deniers can easily post something calling into question the scientific consensus on climate change, not a single refereed article in more than a decade has sought to refute it.”

  28. 78
    Timothy says:

    #68 – There’s a poster on the development of the Hadley Centre decadal prediction system at

    Re: #25,21 To clarify I was thinking more of there being no significant action to deloy technology to curb CO2 emissions [rather than not seeing any result of CO2 emissions]. In the UK, for example, the vast majority of the decrease in CO2 emissions [compared to 1990] is due to the switch from coal to gas powered electricity generation that was motivated solely on cost grounds rather than the reduced CO2 emissions.

  29. 79
    C. W. Magee says:

    From the telegraph article noted above:
    “Dick Lindzen emailed me last week to say that constant repetition of wrong numbers doesn’t make them right. Removing the UN’s solecisms, and using reasonable data and assumptions, a simple global model shows that temperature will rise by just 0.1 to 1.4C in the coming century, with a best estimate of 0.6C, well within the medieval temperature range and only a fifth of the UN’s new, central projection.”

    It’s like “Star Trek” science, only you need journal access to find the kinks.

    OK, I’m now motivated to write up what I thought of Jan Veizen’s talk last week.

  30. 80
    James Davey says:

    Onar Ã??m Re #72: The Kyoto Protocol explicitly states that the developed world will take a lead in reducing GHG emissions. I haven’t seen *any* mitigation strategy that impacts of 3rd world development, indeed it is likely that if we secure an effective Global agreement to reduce emissions worldwide (which may or may not occur sometime between now and 2012) a significant part of such an agreement will be a historically unprecidented investment in development.

    If we have 50 years worth of business as usual development the costs impacts of climate change will dwarf the development gains we accure. If, on the other hand, we accept a small additional cost to develop in a low-carbon way, using technologies that are already available, we can tie in to a low carbon future now, saving us $trillions and improving the lives of countless millions.

  31. 81

    Re #69 and “To boldly assert as axiomatic that “change = bad” is, I think, rather naive and simplistic.”

    What’s even more naive and simplistic is to assume that random local changes are likely to be good or at least neutral. When you have a functioning local ecology, change almost always IS bad. That’s not an assumption, it’s an empirical result. Dutch Elm disease. Rabbits in Australia. Shakespeare’s birds. The list goes on and on and on.

  32. 82
    pete best says:

    The USA will not ratify any treaty beyond Kyoto or Kyoto but rather rely on the free market economy or obfuscation and doctoring of climate scientists works in order to keep their economy going under the existing administration. Maybe a democratic government will do climate change policy differently but until then its on the back burner as far as the USA is concerned at the white house level anyway.

  33. 83

    I find RealClimate a very source of information and analysis, but I have my doubts about these particular calculations. So I have a question.

    You say “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%.” But given that the sinks are large (surface ocean = 1000 Gt; deep ocean 38,000 Gt (figures from NASA website); sediment = very, very large (all the limestone in the world), then one would expect the peak airborne fraction to be very dependent on the rate of adding C02 to the atmosphere. Hence, with the scenario of C02 emissions limited so that the current rate of adding C02 to the atmosphere drops to zero, one might see a very different peak airborne fraction.

    My questions are
    – What are the C02 emissions profiles (vs time) for which the peak airborne fraction is 50-70%?
    – Have the carbon cycle models been run with your scenario (of limiting C02 emissions to 4 Gt C/year)?

    Regards and thanks for all the work you do in running this very useful site.

    [Response:All of the models release their CO2 over several centuries. If it were much faster or slower, you’re right, the airborne fraction would be different. No, I don’t think the the 4 Gt C / year case has been run and published, but I have tried it and it works in the interactive carbon cycle model I posted on the web as part of my new textbook for non-science major undergraduates, to be shipped any day now, called Global warming: Understanding the forecast. The interactive web-based carbon cycle model is here. David]

  34. 84
    Tom Fiddaman says:

    Re 73

    Thanks for the pointer. Nearly all of the studies included suffer from the problems I cited above. As Tol notes, the results are heavily influenced by discount rate choices. So really, the conclusions are not an measure of cost, they’re a measure of willingness to pay, under the assumption that you treat climate the way we treat other things, that is with neither foresight (weight to our grandchildren = 5% of weight to us) nor fairness (weight to China = 5% of weight to USA), with some rosy economic equilibrium assumptions thrown in for good measure. Economists should instead make their models available for experimentation, so people can see undiscounted costs and make their own ethical choices about them.

  35. 85
    Jerry McManus says:

    While looking for info on a book called “Feed or Feedback: Agriculture, Population Dynamics and the State of the Planet” by Duncan Brown (Emeritus Professor; Department of Biological Sciences; University of Wollongong), I was surprised to find this recent essay by him:

    He seems to dismiss that atmospheric CO2 is the primary culprit in global warming and proposes that “the heat produced by enormous increases in rates of combustion” has at least as much influence on the global mean temperature as CO2, at a rate of 0.06 deg C annually.

    He seems to have a good grasp of the basic facts, and he doesn’t strike me as being a crackpot or in the business of denial, but I’ve never heard this idea discussed before. Can anyone here comment? Is the waste heat from combustion part of the climate models? If not, then should it be? Thanks!

  36. 86
    James says:

    Re #69: You say “Even if one assumes the premise that we are “optimally adapted” to the present climate (which I think would be difficult to rationally defend), it does not follow that changes to the climate would result in net costs.”

    Yet by the same logic, it also does not follow that 1) there would NOT be net costs; and 2) the measures needed to limit CO2 would not create net benefits rather than costs. Take the conversion from horses to automobiles for an example. Were there not many costs associated with that? Capitalists had to build factories to produce cars, individuals had to spend money to buy them, roads had to be improved, a whole fuel infrastructure had to be developed, etc. The cost of all that fairly boggles the mind, doesn’t it? Why on earth are we not living in an impoverished world, having spent all that money dealing with the horse manure problem?

    “To boldly assert as axiomatic that “change = bad” is, I think, rather naive and simplistic.”

    But in fact you seem to be the only one making that assertation. The assertation we’re making is that some PARTICULAR changes are bad; we want to see other changes made instead. You’re the one who’s arguing for business as usual :-)

  37. 87
    L. David Cooke says:

    RE: #49

    Hey Hank;

    Just wanted to share that Georg Hoffman helped me understand the point you and David appeared to be trying to explain.

    If the total oceanic CO2 sequester was biologic in nature and the value were 2 GT C then raising the total plankton population 3% would only possibly affect the additional sequestering .06 GT C. To strike a balance the amount would have to increase roughly 67 times the current amount in the hope to achieve a balance point.

    When looking at the biologic free zones as less then 1/3rd the oceanic total would indicate that there simply is not enough means to create a sink large enough without have a possible negative impact in the environment.

    My thanks for the enlightenment, I believe this also nullifies my theory regarding UV impact on ocean biologics and the calls into question the value of the impact of phytoplanton on cloud formation. When tied into what appears to be only an 8% increase in clouds they really must not be play as much a part as I had thought.

    [Response:The main way that fossil fuel CO2 is stored in the ocean is as dissolved carbon, mostly in the form of bicarbonate ion, not as living carbon. There isn’t really much actual mass of living carbon in the ocean. But the sinking dead plankton can carry the carbon around, by forming up in the sunlight and then decaying in the deep. So if you could make the plankton grow faster, they might carry more carbon to the depths, is how the reasoning goes. You can fertilize plankton by adding iron, in the real ocean; that has been shown. But it hasn’t been observed to be very good at carry carbon out of the surface to the deep. And even if you could fertilize the entire Southern Ocean, no easy task, models don’t show it making much difference to the CO2 in the atmosphere. It takes to long for the ocean to change the concentration in the atmosphere, so tugging on the ocean is not very effective. David]

    RE: #85

    Mr. McManus;

    We had talked about that last year in my Environmental Physics class and it appears to relate to entrophy being introduced. I believe the end result of our discussion there was if all the energy that was incorporated in the combustion fuels originated as incoming solar energy and then release back to the environment equaled the incoming it would not be much of an issue. It was when you added to the atmosphere, a energy value greater then came from the sun, that there appeared to be an issue. (Hence, fossil fuels and nuclear sources would increase entrophy, where the use of renewables that were not primarily used for heat would not increase entrophy as much (IE: Energy for motion (an Electric Vehicle), or light (LED lights)). The intent was to suggest that the use of combustion of biodiesel and ethanol or even methane was not preferrable over fuel cells, solar cells, wind energy or tidal energy.

    Dave Cooke

  38. 88
    yartrebo says:

    Re #85:

    Those figures are far off the wall. It’s pretty easy to calculate the heat coming from combustion (avg. energy value of coal * usage + avg. energy value of gas * usage + … etc). I don’t have all the figures offhand, but if you do that calculation, you’ll see that it amounts to some mW/m^2 if spread out over the Earth’s surface – in other words, several orders of magnitude smaller than CO2 forcings which are a few W/m^2.

  39. 89
    Hank Roberts says:

    Grammar, folks, grammar: verb =/= noun and that’s where James went wrong.

    David wrote: “The best would be to not change climate at all”

    — “change” as David Archer uses it here is a verb. The subject is understood: humanity, during the past say 200 years, as we were and are.

    James wrote: “To boldly assert as axiomatic that “change = bad” is, I think, rather naive and simplistic.”

    — “change” as James Annan uses it here is a noun.

    Let me try rewriting for both of you:

    For David:

    The best behavior would have been for us not to have initiated climate change at all,
    — without knowing we were initiating the changes
    — without choosing to initiate the changes
    — without choosing the rate of change
    — without knowing what the changes will be
    — without a baseline (needed for knowing what’s changed), and
    — over a timescale far longer than a human lifespan

    [Response:nicely written. David]

    For James:

    Climate sensitivity is about 3 degrees. To boldly assert as axiomatic that “change = bad” isn’t what you said, but it’s how the innumerate may understand you. That ignores rates of change, and isn’t what you meant.

  40. 90
    L. David Cooke says:

    RE: #87


    To correct an error, that would be 67 times the original proposed 3% or double the current Phytoplankton population. Sorry, in a rush and failed to follow through.

    Dave Cooke

  41. 91
    Hank Roberts says:

    This keeps unfolding.

    “ATLANTA, Nov. 7 (UPI) — U.S. scientists have found a potentially important mechanism by which chemical emissions from ocean phytoplankton influence cloud formations.

    “Discovery of the new link between clouds and the biosphere grew from efforts to explain the increased cloud cover observed over an area of the Southern Ocean, where a large bloom of phytoplankton was occurring…..”

    Production of isoprene has been written about as another possible mechanism for plankton to affect clouds for a decade or more. This seems to be a confirmation in the field of a speculation from the lab work.

  42. 92
    Ender Wiggen says:

    Reply to #82
    The US’s position in not ratifying Kyoto is that it makes no sense to do that unless the whole world complies (including China) and not just a subset of countries. All Kyoto does is drive CO2 production from developed countries to developing countries not impacted by carbon restrictions. The net result will be the same amount of C02 in the atmosphere and economic hardship for countries impacted by the restrictions.

    This is why the US Senate unanimously passed (95-0 ,including all Democrats BTW) a resolution in the late 1990’s against the Kyoto resolution. The greenhouse effect does not care whether C02 is produced in the US or China, today or in 1880, it still has the same warming effect. By treating some of the world’s worst polluters and CO2 generators in one category (developing countries i.e. Annex 2) with no restrictions and developed countries (annex 1) in another with severe restrictions, does not solve anything.

    Only when this loophole is closed will the US and other countries consider restrictions.

  43. 93
    Serinde says:

    RE: 22, 27, 54.
    And thank you, Alastair McDonald at 40.
    Sorry to haul you all back to the press (and I enjoyed the grammar lesson), but I do hope someone takes the time to get to grips with Monckton and Milloy. I’m sure I’m not the only one who wants to blind ’em with science.

  44. 94

    Re #85 and “He seems to dismiss that atmospheric CO2 is the primary culprit in global warming and proposes that “the heat produced by enormous increases in rates of combustion” has at least as much influence on the global mean temperature as CO2, at a rate of 0.06 deg C annually.

    He seems to have a good grasp of the basic facts, and he doesn’t strike me as being a crackpot or in the business of denial, but I’ve never heard this idea discussed before. Can anyone here comment? Is the waste heat from combustion part of the climate models? If not, then should it be?”

    Human energy generation is on the order of 10^13 Watts, Solar power incoming is closer to 10^17 Watts. The added heat from combustion is too trivial to use in climate models.

  45. 95
    Steve Reynolds says:

    Re 84> …the conclusions are not an measure of cost, they’re a measure of willingness to pay, under the assumption that you treat climate the way we treat other things…

    I do not see how you can justify treating climate differently. If someone in India (or anywhere) wants to spend the new money he is earning (due to economic growth) on healthcare to save the life of his child, are you justified in telling him his increased earnings must be taken to spend on reducing CO2 emmissions? How he values future costs is his decision, not yours.

    [Response:Although there is the issue of fairness, to people of the long-distant future as well as others on Earth now. My opinion is that it’s a bad idea for any individual, from India or the U.S. or wherever, to be allowed to follow their self-interest in regards CO2 emission to the atmosphere. It’s a tragedy of the commons thing. David]

  46. 96
    Bryan Sralla says:

    Re #59: Gavin, thank you for the eloquent clarification. I now understand your point, but there are a host of ideas expressed in your comments that I disagree with, but do not have enough space to articuate them properly here.
    That oil will be gradually phased out over the next 150 years is an economic certainty as oil becomes more expensive to extract(we run out of *cheap* sources of oil), and other forms of energy become more cost competative. It is clear then that civilization will be forced to adapt some kind of low carb diet, similar to the regiment I am currently on. It is not pleasant! It is not clear to me however, that governments should impose a quick starvation diet on society. If I am too fat, my obesity might eventually kill me. The wrong diet might kill me quicker though.

  47. 97
    Hank Roberts says:

    > how he values future costs

    The question is how he values future costs he imposes on others by actions that benefit him — “externalized costs” in economic terms.

    The answer at first seems to depend on political views, but doesn’t divide in any simple ways. What Hardin called “the tragedy of the unmanaged commons”

    is, for only one example, not a worry for one subset of libertarians, and it is taken seriously and thoughtfully by another subset:

    Any other group you pick will have some who do and some who don’t try to reduce damage they do to others while acting in their own interest.

    The extreme lack of any such concern may be called sociopathic in an individual or “shareholder maximization” in a corporation.

    It’s not a simple issue; those who see it as one worry me.

  48. 98
    Steve Reynolds says:

    Re 97 and David’s response to 95> It’s a tragedy of the commons thing.

    My point is not that the cost of emmitting CO2 to the commons should be ignored. My point is that the economist peer reviewed consensus marginal cost of about $14/tC should at least be the starting point of discussion.

    Arguing that we should ignore the discount rates and value of future consumption that are implied by the actions of real people (as studied by economists) appears to me to saying ‘we experts’ should make their decisions against their wishes.

  49. 99
    Hank Roberts says:

    Aside — from the OED, examples of ‘change’

    As a noun:

    1553 – EDEN Treat. New Ind. (Arb.) 31 marg. note,
    Chaunge of ayre is daungerous.

    1733 – MISS KELLY in Swift’s Lett. (1768) IV. 47
    For God’s sake try the change of air.

    As a verb:

    1393 – GOWER Conf. III. 109
    He shall his place chaunge And seche many londes straunge.

    1603 – DRAYTON Bar. Warres IV. xxxiv,
    Changing the Clyme, thou couldst not change thy Care.

  50. 100
    yartrebo says:

    Re #98:

    Where do economists come up with that $14/tonne figure? Over 100 years, just changing the discount rate by 1% will change the cost by e (~2.7171). A person using a 0% discount rate and a person using a 10% discount rate will differ by e^10, or roughly 22,000 times over a 100 year span.

    Personally, I like to use a 0% discount rate for such non-monetary things, and the inflation rate for money-denominated things.