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Losing time, not buying time

Filed under: — raypierre @ 6 December 2010

Control of methane, soot, and other short-lived climate-forcing agents has often been described as a cheap way to "buy time" to get carbon dioxide emissions under control. But is it really?

Expectations for the outcome of the Cancun climate talks seem to be running low, and the suggestion has emerged that maybe we should forget about controlling CO2 emissions for now, and instead do something with short lived climate forcing agents like methane or soot. This is often described as "buying time" to put CO2 emissions controls into place. For example, in a recent New York Times Op-Ed, Ramanathan and Victor write:

"Reducing soot and the other short-lived pollutants would not stop global warming, but it would buy time, perhaps a few decades, for the world to put in place more costly efforts to regulate carbon dioxide." — Ramanathan and Victor

The idea that aggressive early action to control short-lived climate forcing "buys time" to do something about CO2 has often been pushed in the past, e.g. in various newsletters and press releases associated with the UNEP Atmospheric Brown Cloud program, for example

"The BC reduction proposal is not proposed as an alternative to CO2 reduction. At best, it is a short term measure to buy a decade or two of time for implementing CO2 emission reduction strategies." — Ramanathan, writing in the UNEP Black Carbon Newsletter.

To be fair, it should be acknowledged that such pleas for more attention to short-lived climate forcing are almost invariably accompanied by a salutary reminder that it is really CO2 that needs to be gotten under control, as in the quote above. Achim Steiner, writing in the same issue of the Black Carbon Newsletter writes "Paying attention to black carbon should not distract people from the real issue at hand, carbon dioxide." A similar sentiment is expressed in the Ramanathan and Victor op-ed. While emphasizing the central importance of CO2, Penner et al. argue that "…to provide short-term relief from climate warming, the short-lived compounds that induce warming need to be brought under control within a timescale of a few decades." (They also make the intriguing suggestion that doing so might provide a global experiment that could help constrain climate sensitivity.) Writing in Science, Stacy Jackson concludes that "… a focus on CO2 may prove ineffective in the near term without comparable attention to pollutants with shorter lifetimes"

All of this is well-intentioned stuff, none of it denies the central importance of CO2, and I’m sure there are many benefits to be had from reducing soot emissions sooner rather than later. Given the large agricultural component of methane emissions, keeping these emissions from growing in the face of a the need to feed a growing number of people is a serious challenge that must ultimately be met. But still, these proposals tend to convey the impression that dealing with the short-lived forcings now will in some way make it easier to deal with CO2 later, and that’s wrong. In this post, I will explain why.

To get a feel for the issues in play, we’ll first take a look at methane vs CO2. This provides a clean example, because methane has a straightforward, well-characterized warming effect which is easy to compare with that of CO2. If you’re just looking at the concentration of methane and CO2 at a given time, the methane/ CO2 equivalence is pretty easy to figure, since you can turn them both into the common currency of top-of-atmosphere radiative forcing. For example, doubling CO2 from 300 ppm to 600 ppm yields a clear-sky radiative forcing of 4.5 W/m2. Doubling methane from 1ppm to 2 ppm yields a radiative forcing of 0.8 W/m2, but since we started from such a low concentration of methane, it takes many fewer molecules of methane to double methane than to double CO2. Per molecule added, methane yields about 54 times as much radiative forcing as CO2. Note that most of this effect has nothing much to do with any special property of methane, but arises simply because the radiative forcing for most greenhouse gases is logarithmic in concentration, so you sort of get the same radiative forcing for everybody upon doubling their concentration — but if you start with somebody whose concentration is low, it takes many fewer molecules to double. That means that the CO2 equivalent of methane depends on what concentration you are starting with. If you started from a concentration of 10ppm, then the equivalence factor drops to 10. If you start out with equal amounts of methane and CO2 (300 ppm), then the equivalence factor drops further to 0.5. In that sense, methane is, intrinsically speaking, a worse greenhouse gas than CO2, though the crossover is at values that are so high they are only relevant (at most) to the Early Earth. ( I ran these calculations with the Python interface to the NCAR radiation model, provided in the Chapter 4 scripts of my book, Principles of Planetary Climate. They are done using an idealized clear-sky atmospheric profile, so the numbers are a bit different from what you’ll find in the IPCC reports, but it’s nice to have a calculation simple enough you can re-do it yourself.)

Things get a lot trickier when you try to bring time into the problem, because methane and CO2 have vastly different atmospheric lifetimes. Methane oxidizes to CO2 in about 10 years, and since we are dealing with so little methane, that extra ppm of CO2 you get after it oxidizes adds little ongoing warming. That means that the methane concentration in the atmosphere is determined by the methane emission rate averaged over the previous ten years, and the methane component of warming disappears quickly after emissions cease. In contrast, about half of CO2 emitted disappears into the ocean fairly quickly, while the other half stays in the atmosphere for thousands of years. Therefore, the atmospheric burden of CO2 in any given year is determined by the cumulative emissions going back to the beginning of the Industrial Revolution, and the warming persists for thousands of years after emissions cease. Over the long term, CO2 accumulates in the atmosphere, like mercury in the body of a fish, whereas methane does not. For this reason, it is the CO2 emissions, and the CO2 emissions alone, that determine the climate that humanity will need to live with for a time that stretches into the future at least as long as the time since the founding of the first Sumerian cities stretches into the past. The usual wimpy statement that CO2 stays in the air for "centuries" doesn’t begin to convey the far-reaching consequences of the amount of CO2 we decide to pump out in the coming several decades.

As a reminder of that, here’s a graph from the NRC Climate Stabilization Targets report (of which I was an author) summarizing how cumulative carbon emissions set the climate thermostat for the next 8000 years and more.
NRC Cumulative Carbon effect on Climate
The numbers on each curve gives the total cumulative carbon emissions (in gigatonnes) during the time when human activities continue to emit carbon. These results are based on calculations by Eby et al using the UVIC coupled carbon/climate model, and they are really just a reprise of what Dave Archer has been telling all of us for years (e.g here, here and here). It turns out that it matters little to temperature whether all the CO2 is emitted in a carbon orgy near the beginning of the fossil fuel era, or spread out over a few hundred years. It’s cumulative carbon that counts, and pretty much it is the only thing that counts. A cumulative emission of a trillion tonnes of carbon just might keep the Earth below a warming of 2ºC, in line with earlier estimates equating the European Union target warming threshold with cumulative carbon (see our Trillion Tonne post). The peak warming scales approximately linearly with cumulative emissions, and the warming you get at the peak is pretty nearly the warming you are stuck with for the next millennium, with only slight declines beyond that. We are currently about halfway to our first trillion tonnes, but given the miracles of exponential growth, we are going to get there pretty quickly if nothing changes. If you go beyond, and dump 2355 gigatonnes into the atmosphere before kicking the fossil fuel habit, then the global mean temperature will still be 3ºC warmer than pre-industrial in the year 8000. That gives plenty of time for bad stuff to happen, including deglaciation of Greenland, loss of the West Antarctic Ice Sheet, or a destabilizing PETM-type soil carbon release. Note further that these calculations were done with a model designed to have a climate sensitivity similar to the IPCC median. Therefore, even if you hold the line at a trillion tonnes, there is still about a 50% chance that warming will exceed 2ºC.

Let’s suppose, however, that we decide to go all-out on methane, and not do anything serious about CO2 for another 30 years. To keep the example simple, we’ll think of a world in which methane and CO2 are the only anthropogenic climate forcing agents. Suppose we are outrageously successful, and knock down anthropogenic methane emissions to zero, which would knock back atmospheric methane to a pre-industrial concentration of around 0.8 ppm. This yields a one-time reduction of radiative forcing of about 0.9W/m2. Because we’re dealing with fairly short-term influences which haven’t had time to involve the deep ocean, we translate this into a cooling using the median transient climate sensitivity from Table 3.1 in the NRC Climate Stabilization Targets report, rather than the higher equilibrium sensitivity. This gives us a one-time cooling of 0.4ºC. The notion of "buying time" comes from the idea that by taking out this increment of warming, you can go on emitting CO2 for longer before hitting a 2 degree danger threshold. The problem is that, once you hit that threshold with CO2, you are stuck there essentially forever, since you can’t "unemit" the CO2 with any known scalable economically feasible technology.

While we are "buying" (or frittering away) time dealing with methane, fossil-fuel CO2 emission rate, and hence cumulative emissions, continue rising at the rate of 3% per year, as they have done since 1900. By 2040, we have put another 573 gigatonnes of carbon into the atmosphere, bringing the cumulative fossil fuel total up to 965 gigatonnes. By controlling methane you have indeed kept the warming in 2040 from broaching the 2C limit, but what happens then? In order to keep the cumulative emissions below the 1 trillion tonne limit, you are faced with the daunting task of bringing the emissions rate (which by 2040 has grown to 22 gigatonnes per year) all the way to zero almost immediately. That wasn’t very helpful, was it? At that point, you’d probably like to return the time you bought and get a refund (but sorry, no refunds on sale items). More realistically, by the time you managed to halt emissions growth and bring it down to nearly zero, another half trillion tonnes or so would have accumulated in the atmosphere, committing the Earth to a yet higher level of long-term warming.

Suppose instead that you had focused all efforts on reducing the growth rate of CO2 emissions from 3% to 2%, averaged over 2010-2040, forgetting about methane until the end of that period. In this scenario, the cumulative carbon emitted up to 2040 is only 713 gigatonnes, giving more time to avoid hitting the trillion-tonne threshold. The warming from CO2 in 2040 is about 1.2C, but we have to add in another 0.4ºC because we haven’t done anything to bring down methane emissions. That brings the warming to 1.6C, which will increase further beyond 2040 as the cumulative carbon emissions approach a trillion tonnes. However, since methane responds within a decade to emissions reductions, we still get the full climate benefit of reducing methane even if the actions are deferred to 2040. The same cannot be said for deferral of action on CO2 emissions.

The following cartoon, loosely based on Eby’s calculations shows two illustrative scenarios: one in which early action is taken on methane, at the expense of allowing cumulative CO2-carbon emissions to rise to around 1.7 trillion tonnes, and another in which action on methane is delayed until 2040, allowing cumulative emissions to be held to a trillion tonnes. The curves can be diddled a bit depending on how much short term warming you get from controlling additional short-lived gases, and how much extra cumulative carbon emissions you assume goes along, but it is really hard to come up with any scenario where you come out ahead from acting early on the short-lived forcings instead of going all-out to reduce the rate of CO2 emissions.

There are a few greenhouse gases other than CO2 that have lifetimes sufficiently long to lend some urgency to their control. That would include HFC23 with a lifetime of 260 years, CFC13 with a lifetime of 640 years and SF6 with a practically unlimited lifetime. Most of the rest are more like methane than they are like CO2 (e.g HFC31 at 5 years)

Absorbing aerosols — soot, loosely speaking — have a number of complex regional effects that make it difficult to treat their climate impact on an equal footing with that of well-mixed greenhouse gases. Soot falling on snow or ice has an unambiguous warming effect, manifest particularly strongly at high latitudes and high altitudes. For airborne absorbing aerosols, though, it is hard to even know whether they have a warming or cooling effect on surface temperature, or leave it more or less unchanged. Except over high albedo surfaces, airborne aerosols mainly heat the atmosphere by direct solar absorption, at the expense of reduced solar absorption at the surface. When the shading is not too strong, the main consequence is a reduction of the convection that would ordinarily carry solar energy from the ground to the atmosphere. This profoundly influences precipitation, and the atmospheric circulation, especially in the tropics. In extreme cases, the atmospheric absorption can even shut down convection completely, leading to stabilization of the tropospheric lapse rate and a severe surface cooling, as in the Nuclear Winter limit (see also the more elementary discussion of this limit in Chapter 4 of Principles of Planetary Climate).

A further consideration is that most activities that emit soot also emit precursors to reflecting aerosols which cool the planet. It is unlikely (and probably undesirable) that one would be able to limit one without also limiting the other. Hence, the net implication of the black carbon component is probably that it will help offset some of the warming caused by eliminating sulfate aerosols. That’s good, but it’s not what you bargained for if you were expecting a cooling for your money. The main thing about soot and the stew of toxic emissions going into the Atmospheric Brown Cloud , though, is that there are compelling human health, agricultural, and regional climate reasons to eliminate them, regardless of the side effect on global temperature. These are things that need to be done regardless of the climate implications (positive or negative), just as there is a need to supply the developing world with reliable clean water. It is pointless to make an already complicated climate negotiation yet more complicated by wrapping such things into the mix. It is nonetheless worth noting that many of the things one would do to reduce soot emissions, such as substituting natural gas for coal, or burning coal in cleaner, more efficient power plants, also would tend to reduce CO2 emissions, and such double-wins are of course to be sought and pursued ardently (note Gavin’s op-ed on co-benefits of CO2 reduction).

IPCC-style Global Warming Potentials attempt to trade off radiative forcing against lifetime in a Procrustean attempt to boil all climate forcings down to a single handy-dandy number that can be used in climate treaties and national legislation. In reality, aerosol-forming emissions, short-lived greenhouse gas emissions, and CO2 emissions are separate dials, controlling very different aspects of the Earth’s climate future. CO2 emissions play a distinguished role, because they ratchet up the Earth’s thermostat. It’s a dial you can turn up, but you can’t turn it back down. CO2 is a genie you can’t put back in the bottle. Climate forcings should not be aggregated. Each category should be treated in its own right. Otherwise, there are perverse incentives to do too much too soon on short-lived forcings and too little too late on CO2.

379 Responses to “Losing time, not buying time”

  1. 51
    Jim Galasyn says:

    Re methane emissions from permafrost:

    “It’s taking place now, and we are too late, to my mind, for decision making. This process has started, and we have no opportunity to stop it. We have only a time to delay it, to make the results less horrible.” — Dr. Sergei Kirpotin, Biologist, Tomsk State University

    BBC video: Russia permafrost melt – ‘We have no opportunity to stop it’

  2. 52
    Jacob Mack says:

    Dr. Sergei Kirpotin is mistaken.

  3. 53
    M says:

    I’ve been working on this issue for a while, and have come to two sort-of-gelling thoughts on the benefits of short-lived forcer reduction:

    1) Reduce near-term rate of change (possibly to counteract cooling aerosol reductions). This has near-term benefits, and _may_, due to the positive feedbacks in the system, actually have much longer term effects than would be naively calculated from first principles by just looking at the time scale of radiative forcing.

    2) In a world where CO2 _will_ be controlled, then continuous short-term forcer control can actually lead to \peak shaving\. I think Kopp & Mauzerall may have been an example of this?


    1) Neither 1 nor 2 provide any notion of \buying time\. I agree with this post’s authors that \buying time\ is the wrong way to think about this. The NRC Stabilization Report actually said that in fairly strong language (search for the word \fallacy\ in the Report).

    2) I’m still on the fence about the benefits of reducing instantaneous BC emissions. You get 2 weeks of forcing reductions, maybe a few months of temperature reductions: not worth much. However, reduction measures are rarely instantaneous: a diesel particulate filter on a new truck engine will lead to 20 years of emission reductions. Home-based wood stoves hang around for up to half a century or more. And behavior shifts such as getting people to switch to cleaner cookstoves can last up to a lifetime (though then the question of \counterfactual\ arises: absent a BC policy, how long would it take for development to get rid of cookstoves anyway?). So these infrastructure investments have lifetimes much longer than BC, making it more valuable to reduce.

    2b) However, CO2 is, I would argue, much more sticky-infrastructure based than BC is. Coal-fired power plants are 50 year+ behemoths. Suburban sprawl commits us to personal transport vehicles for probably the next century… and decarbonizing the transport sector is more challenging than the electric sector (it probably requires electric decarbonization as a first step). Building efficiency improvements are similarly 50+ year payoffs of energy-use, and therefore CO2-use reductions.

    Anyway, thanks for a thoughtful commentary. And I’d suggest looking up the \fallacy\ language from the NRC report and citing that in your statement.


  4. 54
    Russell Seitz says:

    war to Bart’s attention.

    Semantic aggression can backfire as skepticism, and the NAS gently excoriated t TTAPS lack of realism in concatenating worse-case assumptions to front load a one dimensional ” baseline” model by excluding the expression ” nuclear winter ” from the sober pages of its report.

    Modelers, including systems programmers, who aim for maximum political effect by red-lining the Precautionary Principle should recall that Sagan’s woes arose from failing to deliver on his own rhetoric —
    the Foreign Affairs article to which Schneider & Thompson and I replied commenced :

    “Apocalyptic predictions require , if they are to be taken seriously, higher standards of evidence than do those on other matters where the stakes are not so great.”

    [Response: No more about TTAPS and Nuclear winter, please, unless you relate it to my point about the effect of absorbing aerosols on the surface temperature –raypierre]

  5. 55
    David Miller says:

    I would add a third point to Michael Tobis’ answer to The foot-draggers say we should delay policy change for as long as possible because we will be wealthier in the future and better able to afford to act.

    3) The idea that wealth will increase as the climate degrades is utter nonsense.

    Regarding raypierre’s comments on the amount of fossil fuels available to burn (#31), I think it’s necessary to add the ‘unconventional sources’ to the posited amount of coal. As long as there is economic incentive we’ll keep emitting CO2. In-situ combustion or partial combustion of heavy oil/tar sands/deep coal can be economic even when 3 units of carbon are required to liberate 1 unit of carbon as a useful fuel.

  6. 56
    Russell Seitz says:

    re 22 Previous attempt to post lost its first sentence – please post as follows

    BPL asks : ” What do you think the effect of incinerating several hundred cities would be?

    I commend to his attention the contemporary SCOPE and NAS reports on the environmental consequences of thermonuclear war /

    Semantic aggression can backfire as skepticism, and the NAS gently excoriated t TTAPS lack of realism in concatenating at times surreal worse-case assumptions to front load a one dimensional ” baseline” model by excluding the very expression ” nuclear winter ” from the sober pages of its report.

    Modelers, including systems programmers, who aim for maximum political effect by red-lining the Precautionary Principle should recall that Sagan’s woes arose from failing to deliver on his own rhetoric —
    the _Foreign Affairs_ article to which Schneider & Thompson and I replied there and in Nature commenced :

    “Apocalyptic predictions require , if they are to be taken seriously, higher standards of evidence than do those on other matters where the stakes are not so great.”

    [Response: Please, Nuclear WInter itself is off-topic. The only thing that is on topic is the radiative-convective behavior of the atmosphere if you greatly increase the absorbing aerosol content. –raypierre]

  7. 57
    SecularAnimist says:

    Edward Greisch wrote: “The new factory built reactors are so much simpler to operate that the trained operators and physicists are not needed … The [Chernobyl]“disaster” was mostly hype.”

    Moderators: allowing an individual to post outlandish and unsupported claims about experimental nuclear power technology that does not, in fact, actually exist outside of a laboratory, along with equally outlandish and contrafactual characterizations of the Chernobyl disaster, invites better-informed rebuttal — leading to yet another prolonged off-topic argument about nuclear power, of the kind that you have often complained about.

  8. 58
    Andy says:

    Re: reply to #42. Yes, I think. Thanks for the post.

  9. 59
    Hank Roberts says:

    Edward, there are no transuranics in coal and relatively few light fission daughters; mostly heavy metals.

    Similarly for oil:

    From the first link, “hundreds of fly ash particles” have been examined; here’s an autoradiograph picture of one particle; tracks from radioactivity:

    Yeah, come to think of it, that does look like a good argument for not inhaling fossil fuel combustion products, doesn’t it? Quite a few traces out of just one little fly ash particle …. who knew?

    I wonder if anyone’s done that study for black soot from diesel engines?
    Well, there’s plenty of time, it will be coming down in the rivers as the glaciers melt and show up in the sediment.

  10. 60
    Jeffrey Davis says:

    The compromise on the tax issue today showed how negligible is the will to do anything sensible in politics in America. Barring some cinematic catastrophe, we will only address climate mitigation when the efficacy of doing anything is long past.

    So, pray (if you pray) that climate sensitivity is in the low range of the estimates.

  11. 61
    pete best says:


    I have a question regarding the 22 billion tonnes of emissions by 2040. Is that CO2 emissions per annum in total, CO2 emissions that stay in the atmosphere per annum or just carbon emissions per annum?

    I thought that we presntly released around 8-9 billion tonnes of Co2 that when combined with 2xO2 becomes around 28 billion tonnes of CO2 of which 60% is absorbed by sinks leaving around 12 billion in the atmosphere.

    Can you fill me in on this one please?

    [Response: That’s 22 gigatonnes (annual rate) of carbon emissions. I always prefer to deal with carbon as an accounting standard, rather than CO2. –raypierre]

  12. 62
    pete best says:

    Sorry I meant 8-9 billion tonnes of carbon and not Co2.

  13. 63
    ScepticMatthew says:

    40, Hank Roberts: SM: harryrw wrote “It’s about buying time” — Ray followed up inline above: “the implication about ‘buying time’ is just false advertising.” Still happy with harryrw writing that, or will you help explain to him why Ray’s right?

    Still happy, sure. The alternatives to coal are getting cheaper as R&D progresses and larger quantities are mass-produced. I favor a slow phase-out of coal, not pure inaction, over the next 10 years, to be followed by a stronger push when the newer technologies are cheaper than they are now.

    The conjecture that it is “false advertising” is a conjecture.

  14. 64
    David Stern says:

    I don’t think it needs to be so binary or black&white. We need to do both, but by acting on methane etc. the rate at which CO2 emissions need to be cut can be reduced a little. That buys some time. But it would be crazy to do nothing about CO2 till 2040.

  15. 65
    Keith Kloor says:

    #37: “When political reality collides with physical reality, which one do you think will win?”

    Political reality is winning now and looks to keep winning for the foreseeable future. That is the whole point to the NYT op-ed.

    That is not addressed in this post.

    [Response: So political reality is saying “We can’t do this thing that’s really useful,” and i response, you’re saying “Well, we’ll do this thing that instead isn’t all that useful, sing kumbaya and que sera sera.” Do I have that right? –raypierre]

  16. 66
    Adam R. says:

    When the climate going gets tough, the lukewarmers get…muddled.

    Bewildered by the deniers’ sophisticated, tough propaganda, the Times and people like Kloor and Pielke are yelling “Sit still!” in a flaming theater.

  17. 67
    M says:

    “We need to do both, but by acting on methane etc. the rate at which CO2 emissions need to be cut can be reduced a little. That buys some time. ”

    Yes on “we need to do both”, and NO on “the rate at which CO2 emissions need to be cut can be reduced a little. That buys some time.”

    The whole point of this post was to point out that methane reductions today do NOT reduce the rate at which CO2 emissions need to be cut if what you care about is temperature reduction in 2100 (and 2200, and 2300). However, methane reductions today _do_ matter for temperatures in 2020 and 2030 and even 2040. So they are worthwhile, because we will most likely see increasing negative effects of AGW over the next couple decades. But the real doomsday events are more likely to happen near the end of the century and beyond if we don’t get a handle on CO2…


    (note that a world in which we _never_ reduced methane would be a world in which we needed to reduce more CO2 to compensate. But reducing methane _today_ doesn’t change the CO2 target hardly at all)

  18. 68
    Maya says:

    On a related subject (insofar as it speaks to the urgency of Doing Something Constructive), this just popped up:

    If the sub-ocean floor biosphere is biasing the estimates of turnover of the deep ocean water (and they’re not sure if it is), then would that in turn bias estimates of acidification rates?

    [Response: WOW! That is cool indeed, and maybe pretty significant. Thanks for posting –Jim]

  19. 69
    Hank Roberts says:

    > cheaper
    You manage to believe fossil fuel isn’t already the most expensive option?
    You’re ignoring any cost except money?

  20. 70
    Ray Ladbury says:

    RL: \When political reality collides with physical reality, which one do you think will win?\

    MV: \That’s a trick question, right?\

    Would that it were. I suspect human stupidity will prevail just long enough to make Mother Nature REALLY pissed off.

  21. 71
    Christopher Hogan says:

    Excellent, clear article. This answers the question “if we know that many factors affect global temperature, why do we fixate on C02”?

    There’s no faulting your logic. If society trades off reductions in short-lived climate forcings for long-lived GHG reductions, even in a way that is equivalent in the short run, the long run impact will be higher global temperatures. Seems to me that’s just a matter of arithmetic.

    Yet I found this thought-provoking, because it is so contrarian.

    Let me get down to specific. I’ve ordered a 5-gallon bucket of white “zone paint”, suitable for painting asphalt. I’m planning to use it to paint my asphalt driveway white. (I already painted part of my roof white.) As the US DOE has pointed out, increasing urban albedo is an effective way to reduce the immediate impact of global warming. I figured, for $100 and an afternoon of labor, it seemed pretty cost-effective, based on the DOE calculations.

    Now this article comes along. It sets me back on my heels a bit. Comments above have already captured my reactions.

    On the one hand, if we aren’t going to see much action on C02 until we see more effects of warming (in the US, at least), then that creates exactly the tradeoff you don’t want to see. Reducing warming with short-acting factors (e.g, a coat of paint that might last 10 years) is, potentially, the wrong way to go, as it defers action on C02.

    On the other hand, if climate feedbacks such as arctic methane are significantly stronger than current anticipated, then … buying time, in and of itself, might be a laudable goal. But that’s an admission that we might be, even now, at the edge of the pace of change that we can adapt to. I’m not sure I’d believe that yet.

    Back to specifics. I’m not going to use my white driveway as an excuse to emit more C02. So there’s no micro-level tradeoff for me. Given that, should I or shouldn’t I paint it?

    Or, more realistically, is something like the US EPA’s “Cool Roofs” initiative actually sound policy? (Considering only the albedo effect in isolation, not the reduction in fossil fuels for utilities.) Or is it just enabling us to put off some day of true reckoning?

    I’m not talking about pseudo-green (driving the SUV to drop off a bit of recylables, as above). I’m now wondering whether I should start to question the wisdom of some effective strategies for moderating climate change — because they postpone the day of reckoning on C02.

    I guess that’s unknowable. I’m going to paint my driveway and hope for the best. I’d be interested to hear if you have an opinion one way or the other.

    If there were one other thing I could ask, it would be that you point me toward an accessible summary of the evidence behind the IPCC atmospheric residence time assumptions. When I Google it, all I seem to find is obvious nonsense from deniers. Plus the “bomb carbon”, which has a lot of intuitive appeal, but may or may not be a reasonable proxy for C02 atmospheric residence time.) At the IPCC site itself, all I’ve found is the formula itself (three exponentials), not a capsule of the evidence behind it.

  22. 72
    John E. Pearson says:

    63 David Stern said:

    “it would be crazy to do nothing about CO2 till 2040.”

    The US built over 100 GW of nuclear power plants in under two decades. We have the technological ability to build say 500GW of nukes in another two decades. Throw in whatever mix of renewables you want. 1-200 GW of wind. 50-100 GW of PV. Put in heavy tax credits for solar hot water. Quitting coal is eminently doable. Our political system is broken so it won’t happen.

  23. 73
    Keith Kloor says:


    I don’t see how you get that from my comments here.

  24. 74
    John Mashey says:

    Without detracting in any way from Raypierre’s general idea, I do observe there are certainly7 “no regrets” actions focused on methane, such as methane capture for power, from landfills or farms, for example. Unlike most other GHGs, methane is actually useful fuel.

    As long as this is never assumed a substitute for CO2 reduction:

    1)As is: methane => atmosphere, more warming than CO2, until the methane converts

    2) Capture methane => burn to CO2, so remove that extra warming in short term, even if long-term CO2 is same.
    But, depending on where you are, if the generated electricity replaces fossil-fuel energy, that avoids generation of CO2.

    Of course, this is all a small effectt, and one can argue about whether or not it’s a good idea to generate the methane in he first place, but if people are doing it, they might as well capture the energy of natural gas and convert it quicker to a less-strong GHG, if only for long-term energy systems that still work after fossil fuels are no longer usable.

  25. 75

    Raypierre, Great post!!!

    This really puts some truly valuable context on the considerations.

  26. 76
    Geoff Sherrington says:

    Would someone kindly give a direct answer to the questions I put at 19?

    I’m not interested in insults.

  27. 77
    Geoff Sherrington says:

    71 Christopher Hogan says “Let me get down to specific. I’ve ordered a 5-gallon bucket of white “zone paint”, suitable for painting asphalt. I’m planning to use it to paint my asphalt driveway white. (I already painted part of my roof white.) As the US DOE has pointed out, increasing urban albedo is an effective way to reduce the immediate impact of global warming. I figured, for $100 and an afternoon of labor, it seemed pretty cost-effective, based on the DOE calculations.”

    Christopher, can you please explain where the rejected heat goes? Dis it go somewhere that was kind to your neighbours?

    Is there a gain if some is simply sucked into the inlets of adjacent air conditioners in hot climates?

  28. 78
    Daniel Bailey says:

    Re: Jim Galasyn @ 51

    Thanks for the link to that vid.

    Here’s hoping Dr. Sergei Kirpotin is wrong in his conclusion; but I suspect the odds are dramatically against that hope, which fades like a flower at summer’s end…

    Evidence-less drive-bye nay-sayers to the contrary, Kirpotin is well-trained to make the distinction he does.

    The Yooper

  29. 79
    John Mashey says:

    Napoleon had several relevantquotes:

    ‘Go sir, gallop, and don’t forget that the world was made in six days.
    You can ask me for anything you like, except time.’

    ‘The loss of time is irretrievable in war; the excuses that are advanced are always bad ones, for operations go wrong only through delays.’

  30. 80
    dhogaza says:

    Geoff Sherrington:

    Christopher, can you please explain where the rejected heat goes?

    What rejected heat? Look up albedo and continue on from there …

    elsewhere Geoff says:

    I’m not interested in insults.

    Asking questions informed by knowledge would help that situation …

  31. 81
    Adam R. says:

    Keith Kloor says:


    I don’t see how you get that from my comments here.

    No, Keith, I’m sure you don’t. It is part of the the big picture you don’t see.

    You don’t see that the struggle to prevent catastrophic alteration of the climate has reached a desperate stage. You don’t see that flaccid, half-assed ideas like those in the Times article are not merely useless but destructive at this point. You don’t see that your tone-trolling, accommodationist stance is exactly what the climate FUD empire is hoping to provoke in its enemies. You are the Koch brothers’ lap dog, Keith, and you pretend not to know it.

  32. 82
    Josie says:

    Surely we might want to delay warming to give us longer to cope with it, in the (possibly erroneous) hope that in 50 years we might be in a better position to adapt to it than we are now?

  33. 83
    Christopher Hogan says:

    To comment 77: The point of painting the surface white is that visible light isn’t converted to heat, it’s reflected as light. So it (mostly) passes back out of the atmosphere. The white surface stays cooler than the black surface would have been, simple as that. No spillovers to the neighbors, other than the somewhat odd appearance.

    At this latitude (40N), in the summer, the effect on a roof is quite something to experience. Easily 50 degrees F difference between a white roof and a black roof at mid-day. The tradeoff is that the freshly painted roof surface is painful to look at, in full sun, without sunglasses. The compound I used on the roof (Henry Solarflex 287) claims 90% reflectivity when new. (For comparison, the albedo of fresh snow is typically cited at 80 to 90).

  34. 84
    Adam R. says:

    Josie says:

    Surely we might want to delay warming to give us longer to cope with it, in the (possibly erroneous) hope that in 50 years we might be in a better position to adapt to it than we are now?

    Surely. But only if the delay is incremental to permanent reduction in warming. Diversions that allow continued increases in the main villain–CO2–are no help at all.

  35. 85
    ScepticMatthew says:

    69, Hank Roberts: You manage to believe fossil fuel isn’t already the most expensive option?
    You’re ignoring any cost except money?

    If that’s addressed to me, then Yes and No. I don’t expect the external costs of coal to be fully included in the price any time soon. I have written that people have become more aware of those costs and may come to tax coal or charge higher fees (e.g. penalties for pollution when the ash piles flood out over productive land after floods.) However, I don’t expect a major change right away.

    The political reality is that you can do some things right away: harvest methane from land fills and feedlots and subsidize solar (the current most expensive) and wind and convert coal plants to gas; and you can do some things later (one to two decades later): tax coal, build nuclear power plants and mass produce biofuels.

  36. 86
    Walter Pearce says:

    Re: SM #85 — What, other than the climate, would you expect to be different in 20 years that would enable coal to be taxed?

    Fiscally, this is the best time in 60 years for the U.S., at least, to begin taxing fossil fuels. As this chart from Reutersshows, payroll taxes could be cut, carbon taxes instituted, and the overall tax burden remain relatively low.

    Moreover, with California’s rejection of Proposition 23, it would seem that a significant percentage of the population agrees that on climate, “No, we can’t wait.”

  37. 87
    Thomas says:

    77: To add to Chris’s answer.
    Increasing the albedo, does decrease the local area heating, by a bit more than the global, i.e.
    some of the reflected light doesn’t make it through the atmosphere (probably around a quarter). But
    if it had been absorbed, it has only two fates: (1) to be reradiated as longwave (infrared), which has lo
    wer proensity to escape to space, and (2) sensible heat. So his frontyard might be a couple of degrees co
    oler, and maybe his neighbors yards a half degree cooler. So A/C and landscaping water demands should be
    incrementally lowered.

    I just used highly watered down housepaint, and slobbed it on with a mop. But I was only looking
    for a few percent increase in albedo that wouldn’t be too noticable, and would make ten year old
    concrete look a little fresher. You might see a decent decrease in nighttime temperatures, as
    pavement does a great job of storing heat during the day and releasing it at night. And at night
    you often don’t have wind, so the lower heat flux from the driveway might not diluted so quickly.

    But, I think that excepting the desire to imcrease your energy efficiency, if we care about
    the long term, shortterm mitigation at this point in time is undesirable, as it reduces urgency.

    I don’t see how simply slowing the rate of emissions, absent the will to leave unoxidized carbon
    in the ground longterm does any good

  38. 88
    Vendicar Decarian says:

    “Two decades is the amount of time we need to buy to break even, as a rational carbon policy should have set in two decades ago. The way I see it is that the time we “buy” just compensates for our past foolishness, not for our future foolishness.” – 49

    The incoming Republican majority in the House of Representatives has selected the National Science Foundation (NSF) as the first target for a “YouCut Citizen Review”, in which ordinary Americans are being asked to identify “wasteful spending that should be cut”.

  39. 89

    #76–Geoff, the questions you asked sound more rhetorical than anything else–especially in combination with your numerous, often not especially well-founded questions. So I, at least, assumed you weren’t really looking for answers. (That would be something seen a fair amount.)

    I think the post is pretty clear that the time taken to emit the carbon is not very critical:

    It turns out that it matters little to temperature whether all the CO2 is emitted in a carbon orgy near the beginning of the fossil fuel era, or spread out over a few hundred years. It’s cumulative carbon that counts, and pretty much it is the only thing that counts.

    So why would you think that compressing all the emissions into a year would make a difference, even if it were possible?

    Then in #77, you betray a near-total lack of understanding of–well, several crucial issues, to keep it short.

    No offense intended, but to ask useful questions, you need to improve your knowledge of the basics, as I suggested earlier, and dhogaza more recently (and pointedly.)

  40. 90
    Vendicar Decarian says:

    “Christopher, can you please explain where the rejected heat goes? Dis it go somewhere that was kind to your neighbours?” – 77

    It goes up mostly. I doubt if he has any neighbours living over his roof or his driveway.

    Maybe you have relatives who spend their days hovering over your hat.

    [Response: White roofs or white asphalt have a net cooling effect on the planet, in addition to an effect on the urban microclimate. As an earlier commenter noted, the solar energy is just reflected back to space, and doesn’t reappear anywhere on Earth. Globally speaking, the effect is small at any scale likely to be done so the main benefit is in microclimate. It’s a form of adaptation, through reduction in the urban heat island effect, and also helps the global picture through reducing CO2 emissions from cooling costs. Green roofs work mainly through evaporation, and this is different. It has substantial local effects, but the heat is not lost — it is just exported and shows up wherever the water you evaporated condenses. But if the main point is local heat mitigation and reduction in cooling energy, green roofs or land cover also have a benefit. The main argument for any of this is that it reduces CO2 emissions from air conditioning. –raypierre]

  41. 91
    Pete Dunkelberg says:

    Geoff Sherrington, re your questions at # 19, there is an inline response there now. I don’t know if it was there earlier.

  42. 92
    Hank Roberts says:

    > solar energy is just reflected

    Not just reflected, according to a neighbor who long ago was a NASA engineer, familiar with heat management for satellite fuel tanks.

    He tells me high-emissivity surface will work as a heat pump, losing heat to a clear cold sky both day and night, and if the air is close to its dewpoint, can condense water out of the air both outside and in the attic.

    Roofing becomes rocket science. Who knew?

    Same principle used to make ice in the desert:

  43. 93
    Keith Kloor says:

    #65, Ray’s inline response:

    No, you have it absolutely wrong. You seem to ignore the reality being addressed by Ramanathan and Victor, which is that nothing is happening on CO2. The political reality is a stalemate, both in the U.S. and globally. That fact–and it is a fact–underlies their suggestion.

    On the contrary, they see it as as useful kickstarter for the carbon challenge.

  44. 94
    Vendicar Decarian says:

    “He tells me high-emissivity surface will work as a heat pump.” – 92

    Did he fail to tell you that black surfaces cool faster than white ones?

  45. 95
    Martin Vermeer says:

    Ray #70, look up “rhetorical question” :-)

  46. 96
    meteor says:

    Hi raypierre

    The integral of fossil carbon is the most important problem for our future climate.
    So, it is incomprehensible that there is no serious work, in my knowing, on the question of carbon (coal) availability and IPCC itself says nothing about this in AR4.

    You cited Lackner:

    “but when I ran this by Klaus Lackner recently, Klaus thought that hydrocarbon extraction would get so good that we’d probably start running out of oxygen before we ran out of coal.”

    Is this sustained by a publication or another serious work, or is this a joke?

  47. 97

    David Stern,

    I think you’re right that it’s better to not view it so much as an either-or situtaion. We need to do both (tackle long term and short term climate forcings as well as air pollution hazards. Win-win situations such as reducing black carbon are especially useful and probably easiest to get political support for).

    However, I think it’s necessarily correct that “by acting on methane etc. the rate at which CO2 emissions need to be cut can be reduced a little.”

    Because the benefit of reducing shortlived forcings is constant in time, whereas the benefit of reducing long lived forcings grows in time (assuming both types of reductions are permanent). So your statement is only true for a limited timeframe, and not thereafter.

    On a different note, there are quite some differences between the different short term forcings, as Ray also alluded to:
    A focus on BC would be good, as it a) offers strong anciliary health benefits; b) is often connected with CO2 emissions, so it would also help with the prime long term forcing (though it is also often associated with reflecting aerosols, so that’s a caveat to be taken into account); c) it has the shortest lifetime so it has the quickest effect, d) it has a disproportionately large effect on the melting of snow and ice in some of the more vulnerable areas of the world; and e) some of its sources are relatively easy to tackle and/or could be expected to garner more political support (cf. CO2 and CH4).

    That makes soot a very different cup of tea than methane.

  48. 98
    Hugh Laue says:

    #68 Indeed interesting.
    As is this post by Joe Romm on climateprogress, very scary.
    “Veron explains that “the science is clear: Unless we change the way we live, the Earth’s coral reefs will be utterly destroyed within our children’s lifetimes.”

    And in response to my posting of this link on CJN!SA group forum I got this in my email this morning.
    “Thanks for the reef article. I was just scuba diving last month in the Similan Islands National Park in the Andaman Sea in Thailand. I’ve dived there several times and the coral and sea life is spectacular. I was dumb-founded this time to see that most of the hard coral was dead over vast sections of the seabed visible to us on the dives. I spoke to dive instructors who recounted that the Andaman Sea had climbed from its normal 28 degrees temperature to over 33 degrees for two months in April and May. The coral bleached out and with the rainy season high seas it then crumbled into rubble. There was a small amount of hard coral below 20 and 25 metres, but very little survived above that, with the exception of some partially bleached fine table top coral.

    German divers working in the region said the devastation crossed the whole of the Andaman, from India down to Malaysia. The shocking part is that it was so quick and so thorough, none of the bit by bit, slow change but rather a massive and systemic collapse.

    In False Bay, here in Cape Town, the steadily increasing water temperatures now see tropical fish living year round in what should be a cold water ecosystem. The combination of heating, acidification and massive human pollution of the coast lines is placing marine and coastal biodiversity in a perilous position. It will be important for CJN and related media to get the images and meaning out to the African public and policy makers – otherwise the situation is ‘out of sight, out of mind’.”

    This is surely compelling support for the argument for fossil fuel derived CO2 to be classified as a pollutant and be heavily taxed.

  49. 99
    David Painter says:

    Interesting debate, but have questions about the whether it is more important to look at the location of the emissions of CO2 and particulates than just the emphasis on quantity? Have been researching the Vankor and Urengoy Oil and gas fields; they are massive and many have visible gas flares on METOP/NOAA AVHRR images. The world bank estimates approximately 150bcm of gas and other condensates are burnt every year.

    In Russia 1000’s of wells all producing massive amounts of CO2 and particulates at northern latitudes within the arctic circle, surely the location is more relevant than just the quantity? Solar breakdown and dispersal methods and rate of decay are different in the polar regions.

    [Response: Location of soot and other aerosol emissions is important, but CO2 can be considered (for purposes of radiative forcing) well mixed on account of its long lifetime. It doesn’t matter where the CO2 is emitted. -raypierre]

  50. 100