the Air Vent

Because the world needs another opinion

Carbon Reduction

Posted by Jeff Id on June 6, 2011

Guest post by Tony Brown

Two weeks ago I started a thread over at Climate Etc. entitled ‘The futility of Carbon reduction?’ (note the important question mark.)
It came about when I received some calculations on likely temperature reductions from carbon mitigation policies, from a colleague, Ed Hoskins, who in turn had run them past the Chief Scientist of the UK’s powerful Department of Energy and Climate Change.
The article explores the likely cost of an aggressive carbon reduction policy and the practicalities of achieving it, but at its heart was a desire to find out what would be the end result in terms of an actual temperature reduction. Here is the question as posed.

Question: Temperatures are expected to rise by 3 degree Centigrade because of actions we have already taken. If the world collectively closed down their carbon economies what temperature reduction could be achieved?

a)    By 2100 b)    By 2200

(source IPCC AR4 WG1 SPM report pp. 13 and 18  and (20.5)

Please describe your calculations together with caveats or provide a reference/link.

I hope readers here will go through the article to put it all into context as it includes a useful chart of emissions by major countries and the likely cost to of reducing them, according to such official documents as the Stern report.

Climate Etc attracts an eclectic mix of sceptics and ardent warmists and every shade of opinion in between. Consequently what transpired was somewhat remarkable as with over 630 responses to date only one or two people attempted any sort of answer.

This led me to briefly believe that Ed and I were geniuses for thinking up a question that no one had asked before, but reality quickly re-asserted itself that it would be irresponsibility on a grand scale if those advising our governments had failed to undertake the calculations themselves. So those calculations surely exist, but those who believe in CAGW seem reluctant to promote them.

Is it because the answer is one they don’t like? That the vast costs of mitigation and the astonishing social and technological upheavals needed to achieve them would result in a temperature mitigation so tiny as to go unnoticed?

Jeff kindly agreed that I could re-state the question in this forum in the hope that readers will supply answers-complete with their calculations- or alternatively provide a link to an existing study that directly answers the question.

Tony Brown (tonyb)

29 Responses to “Carbon Reduction”

  1. I am in the middle of writing another paper on the energy source of stars – including the Sun – and have neither the time nor expertise in engineering and economics to check the calculations reported here.

    From a purely scientific point of view, I can assure you that the US National Academy of Sciences and the UK’s Royal Society and the research agencies they control have been systematically hiding, manipulating and ignoring experimental observations for decades that show Earth’s heat source is the unstable remains of a supernova that gave birth to the solar system ~5 Gyr ago and continues to generate energy (SE), generate solar neutrinos (SN), and discharge waste products in the solar wind (SW) from:

    a.) neutron emission: 60% SE, 0% SN, 0% SW
    b.) neutron decay to hydrogen: 5% SE, 100% SN, 0% SW
    c.) hydrogen fusion to helium 35% SE, 0% SN, 0% SW, and
    d) exhausting waste products to interstellar space: 0% SE, 0% SN, 100% SW

    Oliver K. Manuel

  2. Brian H said

    Such calculations would logically reduce to choice of sensitivity. Simply ask for the preferred sensitivity, and then for the justifications for that number.

  3. Richard111 said

    Those who can calculate the reduction in temperature for a given reduction in atmospheric carbon dioxide must also understand how the present level of carbon dioxide is raising the global temperature and by how much. Please can I have a link to a valid explanation of how carbon dioxide is warming the planet.

    If I can understand how the warming works this will help me come to terms with the need for reduction in atmospheric carbon dioxide.

  4. timetochooseagain said

    The tricky thing is the time frame. While the forcing would not immediately start to reduce if emissions stopped, it would after a sufficiently long time start to decline-how long depends on how fast CO2 cycles out of the atmosphere. However, we can fairly easily deal with the matter of if concentrations locked in at current levels. According to:

    The current forcing since 1750 from all greenhouse gases is 2.77 W/m^2 which is close to three quarters of a doubling of CO2. A substantial fraction of this forcing is allegedly hidden by “aerosols” mostly particulate pollution. As air quality continues to be improved by modern economies, this masking is supposed to subside. Well, okay, so we can then claim that the forcing that will ultimately be important in our scenario being discussed is the combined greenhouse gases. How much warming is that? Uh, well, that’s tricky, it depends on the climate sensitivity. Well, suppose we use the “IPPC range” of 1.5 K to 4.5 K. Let’s say that the “realized” warming at this point is the “observed” warming since about 1850, about .8 K. I get a range for ultimate additional warming of .323 to 2.569 K. So to me it looks like the three degrees figure requires a sensitivity on the high end of the IPPC range, or even beyond that.

    Alright, so here are some caveats:

    1. This calculation depends on the current forcing from greenhouse gases staying constant if we stop emitting now, while it reality they should eventually start to decline.

    2. The observed warming since 1850 is probably less than the total warming since 1750.

    3. The sensitivity figures from the IPCC are a subject of much debate. This calculation can be done with whatever sensitivity one believes to be correct.

    4. I have not considered here the impact of natural factors either as part of the change since 1850 or how they will change in the future. But since our concern with our “actions” that’s somewhat beside the point.

  5. Steve Fitzpatrick said

    Temperature reduction by 2100: about 0.3C – 0.4C compared to today.
    Temperature reduction by 2200: about 0.5C – 0.6C compared to today.

    This assumes: 1) modest net ocean lag constant (~7.5 – 8.5 years) for determining “heating in the pipeline”, 2) equilibrium climate sensitivity of ~0.45 per watt/M^2, and 3) reasonably fast ocean CO2 absorption due to thermohaline circulation dominating the ocean absorption of CO2 (much faster absorption by the oceans in the out years than projected by the diffusion based Bern model).

    The absence of a crash program to eliminate most CO2 emissions delays the starting point for the inevitable decline by about 40-50 years and increases the temperature peak by about 0.5 – 0.6C, and the decline that follows the peak then will be much more gradual, since some fossil fuels will continue to be burned. Fossil fuels will gradually become too expensive (scarce) for many/most applications, and other energy sources will be substituted; no crash program of investment is needed for this to happen.

    Any reasonable application of discount rates to present day investments show the pure folly (indeed, the insanity) of investing today for an uncertain benefit 100+ years from now.

  6. Charlie A said

    Isaac Held of NOAA GFDL has a paper that looked at the model response to a sudden reduction in CO2 emissions. full text pdf. “Probing the Fast and Slow Components of Global Warming by Returning
    Abruptly to Preindustrial Forcing”

    Much like Willis Eschenbach’s recent series of 1 box models of the full climate models, Isaac Held on his blog, discusses the GFCL GCM and its transient vs. equilibrium responses.

  7. Charlie A said

    The key figure from Held et al 2010 is the plot below

    Perhaps it is an oversimplifications, but it appears that a 1 box model with a time constant in the 3 to 5 year ranges is a reasonable model for the response of the global average temperature to changes in forcings. This corresponds, more or less, to the response of the well mixed ocean layer.

    The longer term response is much more loosely tied to the warming of the deep ocean. The GFDL CM2.1 model predicts that the global temperature would, within a decade or so, return to a small fraction of 1 degree C above historical average were the forcings returned to historical levels today. My interpretation is that this is more or less a reflection of the fact that the deep ocean has increased in temp only a small fraction of one degree C over historical levels.

  8. Charlie A said

    Hmmm.. I messed upon the graphics insertion. is the link.

  9. I think shutting down Co2 emissions would kill most of the people on the planet.

    Aside from that … the temperature wouldn’t change.

    Co2 is a trivial component.

    “The decrease in Earth’s reflectance from 1984 to 2000 translates into an albedo decrease equivalent to a forcing of 6.8W/m^2.”

  10. Steve Fitzpatrick said

    Charlie A,
    The CFDL model (like most CGCM’s) has a) high equilibrium sensitivity, b) high assumed aerosol offsets, and, c) high assumed ocean heat uptake. None of these seems to me very likely correct. Such studies of model behaviors strike me as perilously close to a classic GIGO analysis. The assumption that the model is a fair representation of reality is the most important issue, indeed the only real issue… absent confirmation (via accurate predictions over multiple decades), not much credibility should be assigned to studies of the model’s behaviors.

  11. timetochooseagain said

    Looking again at it, I’m not sure I understand, reduction relative to what? Present temperatures? Zero-as I already calculated there is supposed to be warming “still to come” if models are right, and the forcing won’t go down very quickly, at least with “mainstream” assumptions. Hypothetical future temps? We can possibly talk about “reductions” of that.

  12. Neil said

    Although I spend too much time reading Climate blogs I know far too little, however I decided to have a go at answering the question. I decided to just use the executive summary of the Stern Review. In using this I am not saying that I support it in anyway, I just thought I might piece an answer together from it.
    • Stern says to stabilise current concentrations we need to have emissions below 5GTCO2, the natural absorption rate(page 11)
    • Stern also states that this is more than 80% below the current level of absolute emissions (page 11)
    • Stern states that to stabilise at 450ppm CO2 we need to peak in 10 years and then fall at more than 5%pa to reach 70% below current levels by 2050 (page 11).
    • I will assume that current CO2 is at approximately 400ppm CO2. A graph in the Stern report indicates that at 400ppm CO2 to 450ppm CO2 the temperature rise relative to pre-industrial is between 1.5C to 2.0C (page 5).
    • CO2is also not regarded as the only driver of temperature change and therefore some component of the rise is not CO2related (no citation sorry, please don’t report me).
    • I will assume that changes are instantaneous, that is there are no lags etc.
    So being a former economist I will invoke massive approximations and form the following conclusions and admit that I have not read the larger Stern report, nor have I looked into the cited works for clarification:
    • Shutting down manmade CO2production is close to reducing it to the 70% to 80% reduction that Stern mentions (given all other approximations and measurement errors etc); therefore I will assume the Stern reductions are equivalent to zero man made CO2 emissions.
    • Stern also states that this stabilises CO2concentrations, but in the Executive Summary did not provide a longer term path so I will assume this covers your date period and that stabilisation means flat lining at a given level..
    • Stern also states that 400ppm CO2 to 450ppm CO2 yields a temperate change of 1.5C to 2.0C and we are currently at close to 400ppm CO2, so the current temperature should be close to the 400ppm CO2 to 450ppm CO2 level.
    Therefore we can conclude (based on my casual review of Stern’ Executive Summary) that the effect on temperatures will at best be close to zero relative to current temperatures. Further assuming some portion of the trend is not CO2related we could conclude that the temperature will be higher than current, even if manmade CO2emissions are zero (all other things being equal, an old economic favourite).
    So my answer relative to the 3C rise in your question would be at best 1.5C and most likely less if we assume some fraction of the increase is not manmade CO2 linked.
    I will repeat my earlier caveat. The answer I give does not represent my personal belief, but it was the best a simple guy could manage in less than a lifetime.

  13. Joe Crawford said

    Treating it as a Fermi problem the answer is probably already within the correct order of magnitude. And, that’s close enough for “gov’ment work”. Personally, I’m just glad to see that a bit of engineering reality is finally being applied to the issue of CO2 abatement. We have already spent billions of dollars on the issue, not counting the suffering imposed by increased energy prices, without even an attempt at cost/benefit analysis.

  14. gallopingcamel said


    What mitigation?

    I could not get to the full report you referenced but the following chart does seem to answer one of your questions:

    Apparently the IPCC predicts that the temperature will rise another 0.5 Kelvin if the current C02 levels are maintained. From the shape of the graph one might be tempted to assume a further rise of a few tenths of a degree by 2200. This fits in with the IPCC’s prediction of a long time constant for CO2 in the atmosphere.

    The reason for the continued rise is that particulate emissions are assumed to fall if man made CO2 falls. The warming due to lower particulates causes the temperature to rise rapidly for a while.

    I realize that “Constant CO2” does not correspond to closing down the world economy but it should be quite close.

    Figure 1 in the following report shows a “Zero Emissions” prediction out to 2150 based on climate models that show complex behavior in the “Backcast” versus simple curves in the “Forecast”. I guess a great deal of tweaking went on to enhance the fit back to 1850!

    The PIK paper shows a fall of 0.1 Kelvin after 150 years with zero emissions!

  15. Jeff Id said

    Gallopingcamel, The article is by Tony Brown. IMO there is no way to ‘shut down’ our carbon economies with todays technology.

  16. tonyb said


    Thanks for posting this article on the likely temperature reductions that can be achieved through aggressive carbon mitigation. Within the article there are three elements.

    The first concerns the costs involved. The Stern report was hopelessly optimistic as can be seen from the figures we have produced using this and other sources.

    Second comes the truly awesome technical challenges involved (which you allude to in #15) as the amount of power we need if fossil fuels are to be phased out is simply staggering. Again there are well cited reports that illustrate this.

    So we then come to the third part in which we contemplate the huge costs involved and the immense technical problems, and ask ourselves the question as to what will actually be achieved by way of temperature reduction through undertaking this vast project?

    Bearing in mind the total temperature reduction if the whole world were to close down their carbon economy appears to be tiny-and isn’t going to happen-so the burden is then placed on mostly western countries of which the UK govt are enthusiastic leaders. Even if ALL the enthusiasts-why by now are a small percentage of ALL countries- cut their carbon to nothing the temperature reduction is virtually unmeasurable.

    Whether citizens of these countries realise their govt is sacrificing their economic future by making expensive and ultimately pointless committments to carbon reduction is doubtful. It seems the only voices we hear are those promoting their own green ideologies.

    Consequently the purpose of the original article over at Climate Etc. and this follow up is to try to determine if our calculations on temperature reduction can possibly be in the right ball park.

    Answers so far suggest they are. I don’t know about you but I’m not willing to pay $1500 a year (the Uk’s contribution per person) in order that two thousands of a degree can be shaved off the global temperature in the next 200 years.

    I intend to pose the same question to Scott Mandia, Julia Slingo, Kevin Trenberth and Dr Mueller as it is important to get estimates from those promoting the need for carbon abstinence.
    I look forward to more estimates-I am inclined to agree with Steves estimates in #5


  17. Geoff Sherrington said

    Shortly, poor Australia will be able to answer the question, once the pollies decide on a tax $ per tonne of carbon. Using ballpark figures, Prof Robert Carter calculated “Even according to the IPCC’s faulty models, if Australia stopped all emissions of carbon dioxide from tomorrow, the total effect on the global temperature in 2050 would be to theoretically lower it by 0.0154 °C.”

    The magnitude is of course dependent on sensitivity and feedback numbers as others have noted. The inability of the AGW set to get feedback right is still one of the biggest bloopers. Another is a “robust” calculation of residence times of GHG in the air, for the purposes of correct analysis rather than hand waving.

    The main anser we se here as to why GHG should be reduced now id that “If we do not, they will continue to hasten the heating of the Earth”. Reference his new book, “Climate: The Counter Consensus”. So it’s more about increased emissions than cuts in emissions. Few have the stomach to come out with projections from China, India.

    Tony, I think the lack of answers to your Q is that the resistance had debated it so many times they are bored; and the advocates are ignoring it out of potential embarrasment.

    An interesting set of mitigation costs using wind power ihas recently been released for Australia. Peter Lang has released several discussion papers, this one in Jan 2010

    and two in May 2011

    While the latter do not address your question directly, the provide huge figures for a subset of your question, large enough to make other calculations less relevant.

  18. Mark T said

    They simply cannot answer the question truthfully, in public, without revealing the folly of their need for tax increases.


  19. gallopingcamel said

    Jeff @15,

    Usually I agree with you. Certainly there is zero probability that we will voluntarily give up our comfortable life style that stems from the “Industrial Revolution”.

    Our civilisation could collapse due to nuclear war but in my opinion collapse is much more likely to be caused by pestilence. Something much worse than AIDS. Something even worse than the “Black Death”. Given the greater population density than ever before, a contagion that affects humans as Myxomatosis affected rabbits seems quite likely.

  20. gallopingcamel said

    Geoff Sherrington @17,

    Like you I hang out on Barry Brook’s excellent “Brave New Climate” even though I have to bite my tongue when the denizens trot out their risible anti CO2 mantras.

    Here at the Air Vent I can tell you that while the CO2 emissions created by mankind do affect global temperatures, the effects are generally benign; warming is desirable. Modern temperatures are cooler than recent temperatures in the Medieval warm period, two Roman warm periods and the Minoan warm period. During all of these warm periods civilisation blossomed.

    The cooler periods such as the “Dark Ages” and the “Little Ice Age” were times of unimaginable suffering.

    Looking further back things were positively toasty in the Eocene when there was no permanent ice at either pole and mammals established their current domination of the planet.

    While I support your pro-nuclear stance there are better reasons than CO2 “Mitigation”.

  21. gallopingcamel said

    This camel is in favour of carbon mitigation as long as it is done using the Hammurabi method.

    While Hammurabi lived 3,700 years ago in ancient Babylon he decided to store grain during periods of plenty so that his subjects would have food during the “Lean Years”.

    If our leaders were any good they would be advocating similar policies knowing that an event similar to the 1815 mount Tambora eruption can occur without warning,

  22. Geoff Sherrington said

    Gallopingcamel No, I do not hang out on Barry Brook’s blog. My quality choice includes (but is not limited to) tAV, CA, WUWT, Warwick Hughes, Jo Nova and Niche Modeling. Peter Lang merely chose to release his latest discussion paper there.
    No, I am not stridently pro-nuclear. Having worked in the front end of the nuc industry for much of my career, I think I can distinguish poor articles from quality ones and from the latter, I have seen no compelling anti-nuc argument.
    Have you thought of changing your blog name? Every time I see it I hum this:

    The Sexual life of the camel,
    Is stranger than anyone thinks.
    This weird and mysterious animal,
    Has designs on the hole of the Sphinx.
    But the hole of the sphinx is covered
    By the shifting sands of the Nile,
    Which accounts for the hump on the camel
    And the Sphinx’s inscrutable smile.

  23. gallopingcamel said

    Geoff Sherrington @22,

    My apologies! I must have confused you with someone else. One of the disadvantages of old age is the way your memory plays tricks on you. I like the sites that you list. You might also like Rod Adams:

    The gallopingcamel moniker goes back to my Rugby playing days as a rather large wing three-quarter with a strange running style. Back then we used to sing that song. As I recall, the next verse starts:

    Recent researches at Oxford by Darwin, Huxley and Ball
    Have shown beyond doubt that the hedgehog……………Probably enough of that.

  24. Don keiller said

    Oliver what exactly do you mean by “unstable”?

    The Solar system has existed for some 4.5 G years and life, in one form or another for some 3.5 G years.

    Just how unstable is “unstable”?

  25. […] Tech Football Preview: Red Raider State of the UnionBIU Delivers Financial Statements Up To 2009Carbon Reduction body{background-image:none;} body { background-color: #829def; } WPFP = jQuery.noConflict(); […]

  26. No, I am not stridently pro-nuclear. Having worked in the front end of the nuc industry for much of my career, I think I can distinguish poor articles from quality ones and from the latter, I have seen no compelling anti-nuc argument.
    Have you thought of changing your blog name? Every time I see it I hum this:

  27. burberry said

    The article explores the likely cost of an aggressive carbon reduction policy and the practicalities of achieving it, but at its heart was a desire to find out what would be the end result in terms of an actual temperature reduction. Here is the question as posed.

  28. tonyb said


    The purpose of the article was to explore the temperature reduction we could expect from agressive Co2 reduction policies. The cause and effect being at the heart of a number of western cou ntries policies- most notably that of the UK. The net result is a huge dependance on renewables which unfortunately are extremely expensive and highly inefficient- cerainly as far as the Uks preferred method-wind-goes.

    We have put the question of likely temperature reducytion directly by email to the worlds leading scientist-most of whom don’t seem t have done the calculations.

    The figures are sobering-only around 25% of countries have expressed any serious desire to cut emissions by anything from 10 to 50% . These countries represent a small percentage of all carbon emissions-this percentage is decreasing as other countries-notably China-ramp up their usage.

    The ‘willing’ can have no dscernible effect whatsoeer on temperature yet we are following highly expensive policies that will directly impact on our standrd of living. With petrol (gas) at US$10 per gallon energy prices-doubling over the last five years and deliberately planned to double again in the next five years to provide a ‘carbon’ price floor to make renewables expensive the UK is providing a model of futility and pointlessness.

    Few in the West-and I certainly include the US here-have the money to pursue their grandiose and ideologically driven carbon reduction fantasies withoutr severely impacting on their population.

    Nuclear? I can’t see an alternative-we need energy as the EU is forcing us to shut down our coal fred power stations hence our push for wind. . A 50MW wind farm-usially placed in our most beautiful upland areas-will reduce temperature by ten millionths of a degree and require associated unsightly pylons-all at great cost.


  29. Brian H said

    All fodder for the future booming industry of pylon removal. Invest now!

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