Sunday, May 13, 2012

Nope, Nordhaus is still (mostly) right

[NB: See the UPDATE at the bottom of this post.]

Following our previous tête-à-tête on the Heartland Affair, here's a response to Bob Murphy's latest post on climate change.

In the interests of keeping this as a brief as possible, let me just say that my post follows a back-and-forth involving different groups of people. My aim here isn't to give an overview to the entire discussion, but rather to reply directly to Bob's key points. However, the four act summary is as follows...
  • ACT 1: A group of 16 self-proclaimed climate skeptics write an op-ed in the Wall Street Journal, "No need to panic about global warming"
  • ACT 2: William Nordhaus, professor at Yale University and one of the founding fathers of climate change economics, pens a widely cited essay in response, “Why the Global Warming Skeptics Are Wrong.” Among other things, Nordhaus takes umbrage with the fact that these skeptics have bungled his own research in trying to argue that climate change is not cause for concern. 
  • ACT 3: Enter Bob Murphy, who comes to defend the honour of the original skeptics in his article, "What Nordhaus Gets Wrong".
  • FINAL ACT: Stickman Grant McDermott sweeps in from the shadows to set right the wrongs of the blogging world. Order is restored, women swoon and the sound of childrens' laughter fills the air. Murphy curses and retreats to his secret lair, vowing revenge.

Now that you've seen the plot spoiler, let's go through some details:

1) Global Temperatures Have Been Flat for a Decade

Bob claims that Nordhaus is using a rhetorical slight of hand in addressing the skeptic claim that global temperatures have not increased in 10 years. Nordhaus does this by referring to the instrumental temperature record, which dates back to the 19th century and shows a clear warming trend. Bob claims that this isn't fair, since "no warming in the last decade" and "no warming since 1880" are different statements.

To be frank, this is simply dancing around the issue. If the original claim was meant to serve no purpose beyond itself, then perhaps that would be okay. (Vacuous, but okay.) However, the implication and inference of the skeptics' original statement was abundantly clear: Global warming has stopped, so all this talk about dangerous increases in future temperatures is probably bunk.[*] Nordhaus rightly points out that this is a meaningless observation and that only long-term trends can provide proper context. However, Bob tries to head off this approach too, by providing a long-term graph with rescaled Y-axis; ostensibly to show that temperatures have hardly changed in absolute terms over the last 150 years.

This is simply disingenuous. Let's conduct a simple thought experiment to show why. Imagine that observed warming since the Industrial Revolution isn't caused by mankind, but rather some combination of natural factors. Let's posit that the observed long-term trend due to this natural forcing trend continues unabated, so that temperatures eventually exceed pre-industrial levels by more than 2°C. Will there be economic costs associated with this, relative to a world without warming? Well, according to virtually every single study on the matter, the answer is a clear "YES". If it wasn't, then we wouldn't even be having this discussion... Why do you think adaptation through economic growth is taken so seriously -- not least of all, by prominent contrarians? (Also, see #3 below.)

The take home message is this: Seemingly small changes on the global scale will have tremendous impacts on the climate and natural systems that we depend on. For instance, a 3°C rise in average global temps will correspond to a world that probably hasn't existed for millions of years, entailing massive unknowns and downside risks. Further, the changes in regional temperatures will actually be far more acute, even if these "balance out" to some extent at a global level. (This point is often sadly overlooked by the focus on global averages.)

2) Actual Global Warming Has Been Smaller Than What the Models Predicted

Bob largely bases his comments here on a Master Resource blog post, which in turn cites a paper by Santer et al. (2011). Now, the main purpose of this study is quite technical in that it aims to show how different timescales can affect the ability to distinguish between climate "noise" and "signal". (Ironically, their bottom line is that we gain no understanding of climate change drivers simply by looking at the temperature record from a single decade.) However, we don't really need to concern ourselves with that here. The relevant issue -- and the one that Bob limits his discussion to -- relates to the below graph. It shows temperature measurements of the lower troposphere (TLT), as "observed" by two satellites (RSS and UAH) and predicted by climate models. Without going into specific details, Bob uses this as evidence to suggest that climate models exaggerate the warming effect in comparison to what reality will turn up.

Allow me to make two comments in response. The first thing to note is that satellite temperature measurements appear to suffer from an unresolved cooling bias.[**] Santer et al. (ibid, p. 10) actually highlight this issue in their paper:
“Given the considerable technical challenges involved in adjusting satellite-based estimates of TLT changes for inhomogeneities [Mears et al., 2006, 2011b], a residual cool bias in the observations cannot be ruled out, and may also contribute to the offset between the model and observed average TLT trends.”
In other words, the observed temperatures in the above graph are probably lower than they "should" be. Santer et al. go on to list a bunch of other factors that could also explain the (slight) difference between these satellite measurements and the model predictions. I wish to emphasise that this difference is, indeed, "slight". More fundamentally, this relates to my second point: The models are still remarkably accurate. Again, let's turn to the actual paper (p.10):
“There is no timescale on which observed trends are statistically unusual (at the 5% level or better) relative to the multimodel sampling distribution of forced TLT trends. We conclude from this result that there is no inconsistency between observed near-global TLT trends[...] and model estimates of the response to anthropogenic forcing.”
Translation: The models have performed exactly within the bounds of what we would hope for. I find it... interesting that Chip Knappenberger (author of the MR post) chooses to ignore these caveats and findings, instead offering his readership an alternative conclusion that the models are on the "verge of failing". But then what do Santer & co. know? I mean, they just authored the study.

As for the assertion that Nordhaus is arguing against a strawman by focusing on the role that human activity has played in driving climate change, versus the alternative (weaker?) claim that the models have simply overestimated warming full stop... Let's consider the original WSJ op-ed again: "The lack of warming for more than a decade[...] suggests that computer models have greatly exaggerated how much warming additional CO2 can cause." (Emphasis added.) You could perhaps argue that the statement is ambiguous, but I certainly don't think that Nordhaus is unjustified in highlighting the fact that, only by including CO2 alongside natural forcings, can we square model predictions with observed warming.

For more on the track record of computer models in predicting actual climate outcomes (including reconstructions of the past), see here.

3) CO2 Is Not a Pollutant / CO2 Poses No Harm to Humans

Now we get down to actual economics. Bob declares his unwillingness to wade into a semantic battle of how we define a pollutant... A smart move on his part, since defending the banal assertion that "CO2 can't be harmful because we, like, exhale it and stuff" -- a point that the WSJ skeptics effectively make -- could only lead to much wailing and gnashing of teeth. Instead, he thinks that he's caught Nordhaus at his own game by taking a deeper look at a study that he (i.e. Nordhaus) references in support of his arguments. The paper in question is a literature survey by Richard Tol (2009) entitled "The Economic Effect of Climate". The key figure is below, which Bob uses to claim that CO2 rise will bring net benefits; at least up until two degrees warming. [UPDATE: Bob Ward points out a typo in Tol's paper, which would bring the onset of (expected) negative effects forward. See here for an updated version of the below figure on the And Then There's Physics blog.]

Now, Bob is qualitatively correct here; most models indicate that there are net gains to be had from some moderate level of warming. (Incidentally, this is not something that Nordhaus would appear to dispute.) There are several reasons for such benefits, including increased agricultural production in certain parts of the world. However, some crucial points must be emphasised:
  • Look at the graph and tell me where your "ideal" temperature increase lies. The answer should be obvious: Around 1°C, since this is where we maximise welfare. Anything beyond that and you are doing worse than you would at the 1°C optimum. 
  • The build-up of CO2 is characterised by tremendous inertia. Similarly, it takes thousands of years for CO2 released into the atmosphere to return to natural sinks. Of course, you would also need to consider the structural barriers and delays involved in reorganising your economy away from fossil fuels...
  • Simply put, you almost certainly need to establish a carbon price long before you reach the 1°C turning point... let alone the sharp negative effects that we expect beyond 2°C. Tol actually highlights this in his paper (p. 34): "Policy steps to reduce emissions of greenhouse gases in the near future would begin to have a noticeable affect on climate sometime around mid-century — which is to say, at just about the time that any medium-run economic benefits of climate change begin to decline." To his credit, Bob acknowledges these issues... albeit in a footnote. To my mind, this is such a fundamental matter that I can't help but think that it deserves more than footnote status. (I'd also like to know how he squares these issues with his conclusion that immediate mitigation efforts -- presumably the beginning of some carbon price -- should be cast in "serious doubt".)
Another reason to be very cautious about the benefits of unimpeded CO2 emissions include disproportionately large downside risks (i.e. "fat tails") and, indeed, even regular loss aversion. If someone offers you the chance to flip a coin so that you either win $10,000 with 50% probability, or lose $9,500 with 50% probability, would you take it? I suspect that a clear majority of people would decline to take part in such a game of chance, even though the expected value is positive (i.e. $250). The idea that people value losses more than gains is very well established in the theoretical and empirical literature. Lastly, we would also need to consider the regional disparities in any presumed gains. Africa, for instance stands to be the big loser from climate change, while Eastern Europe wins due to increased agricultural output. Needless to say, this throws up some very thorny ethical issues around the potential benefits that some countries might enjoy at the expense of others.

4) Nordhaus’ Own Work Shows Harms of Government Intervention

Okay, Bob is quick to say that the WSJ skeptics "screwed up" here. Anyone that has read Nordhaus's work knows that he as long called for Governments to put a price on carbon. Still, Bob now offers up one of this own papers to show that... well, it would seem that changing various factors in a climate model can lead to substantially different results. To be honest, I'm not entirely sure what to do with this. Admittedly, I haven't read Bob's paper -- I'll hopefully do so when I get time -- but in his blog post at least he is making some pretty unremarkable points. For instance, Al Gore apparently has some very bad policy recommendations. Okay, but Nordhaus never mentions Gore in his essay and neither do the 16 WSJ skeptics. (Personally, I'm not particularly interested in what AG has to say about the economics of climate change and I certainly can't think of any major nation pushing for 90 percent emission reductions by 2050.) As for the fact that Nordhaus "assumes" that his calibrated carbon tax will be perfectly implemented over time... Um, yes, that's how benchmarks work. We describe the first-best scenario and then look at how deviations from that optimum will impact results.

Nevertheless, let me try to reply in kind by saying that I, too, have nagging problems with Nordhaus' methodology. In particular, using observed market rates for making normative judgments and implicitly assuming perfect substitutability between man-made and natural goods. I have previously written about these issues here and here.

THOUGHT FOR THE DAY: The Wall Street Journal continues to push climate change opinion that is highly misleading and, at times, patently wrong. Bill Nordhaus did us all a service in picking apart some of the more egregious mistakes, as exemplified by this particular op-ed. Bob Murphy makes some interesting points in response, but I don't see that he offers any substantial rebuttals of the fundamental criticisms levied at the "WSJ 16". Nordhaus continues to have the right of this, as far as I am concerned. Obfuscation, begone!

UPDATE: Bob and I are have a little back and forth about this at his blog (also at Daniel's). However what I really wanted to show you is this comment by Richard Tol about his own paper:
It's easy to misinterpret Figure 1 from Tol (2009). 
Initial warming is indeed likely to be beneficial: CO2 fertilization of crops, reduced spending on heating homes, and fewer cold-related deaths are the main factors. 
However, totals do not matter. The incremental impact turns negative around 1.2K. If we were able to control climate, we would warm the planet by 1.2K and stop there. However, the momentum of the climate system and the energy system is such that, if you accept the mainstream view of the workings of the climate, we cannot avoid 1.2K warming, or 2.0K warming for that matter. 
The initial benefit is thus a sunk benefit: We will enjoy it regardless of what we do.
[*] The original WSJ op-ed also makes use of the much misrepresented quote by Kevin Trenberth from the "Climategate" emails. That is: "The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't." For more on that issue, see here.
[**] Part of this probably has to do with the fact that they employ a convoluted modeling procedure to produce temperature readings. For starters, satellites do not measure temperature directly, but rather various signal wavelengths that must then be mathematically inverted to obtain indirect inferences of temperature. I should also say that the UAH temperature set referenced by the Santer et al. study, which is produced by John Christy and Roy Spencer, is particularly contentious. You can read more about these issues here and here.


  1. "For instance, a 3°C rise in average global temps will correspond to a world that probably hasn't existed for millions of years, entailing massive unknowns and downside risks."

    What approximate year do you expect this 3 degree Celsius rise to be achieved?

    1. Mark, of course it depends on many factors. The IPCC has a nice summary of expected mean global temperature rise under different scenarios:

      The short answer is that a "BAU" progression will take us to the three degree threshold (relative to 1980-1999 levels) towards the end of the century.

    2. "The short answer is that a "BAU" progression will take us to the three degree threshold (relative to 1980-1999 levels) towards the end of the century."

      It's interesting that you should use the phrase "BAU," because it doesn't appear on the IPCC page you referenced. What does appear on the page are 6 scenarios. In four of the six scenarios, the warming for 2090-2099 (ralative to 1980-1999) is less than 3 degrees Celsius. But let's say you think that the warming for 2090-2099 relative to 1980-1999 is going to be 3 degrees Celsius. Does it bother you that, in all of recorded history, there has never been a single decade with warming of 0.3 degrees Celsius, but you are expecting warming to *average* 0.3 degrees Celsius or more for the next 10 decades? Don't you think your expectation is slightly unrealistic?

      For example, wouldn't you expect temperatures to rise in response to the logarithm of greenhouse gas concentrations? That is, wouldn’t you expect that a logarithmic increase of greenhouse gases would be necessary to sustain a linear increase in temperatures? And therefore, if greenhouse gas concentrations are increasing less than logarithmically, the temperature increase would be less than linear, rather than greater than linear?

      Also, with regard to Richard Tol’s analysis, it appears that the “best estimate” for damage to the economy caused by a 3 degree Celsius rise would be minus 2.5 percent of GDP. Why do you think we should care whether the people of 2090-2099 happen to experience a 2.5 percent GDP decline relative to if we could miraculously keep temperatures constant? For example, can’t the world GDP be expected to increase by more than 2.5 percent per year…so that trimming off 2.5 percent means essentially that the same GDP that would be reached in 2090 is now reached in 2091, and so on? And why the comparatively poor people of 2012 sacrifice anything for the comparatively rich people of 2090-2099. In 2012, the world per capita GDP is about $10,000 (PPP, 2012 dollars). What do you think the per capita GDP will be in 2095, PPP, 2012 dollars? The world-wide average life expectancy at birth in 2010 was 67 years. What do you think it will be in 2095?

      Finally, you write, “Similarly, it takes thousands of years for CO2 released into the atmosphere to return to natural sinks.” How do you think that statement is relevant? What do you think the world per capita GDP will be in, say, 2162 (150 years from now)…again, in PPP, 2012 dollars?

    3. It's interesting that you should use the phrase "BAU,"...

      Why interesting? Have you read the scenario descriptions? If so, I'm not sure how you could find it objectionable to describe those upper prediction paths as "BAU", i.e. steady economic growth coupled with unregulated emissions. (Incidentally, we are currently on track with the A2 scenario, which is precisely what I have described as BAU...)

      Does it bother you that, in all of recorded history, there has never been a single decade with warming of 0.3 degrees Celsius?... [W]ouldn’t you expect that a logarithmic increase of greenhouse gases would be necessary to sustain a linear increase in temperatures?

      With due respect, you appear to be making some well-worn errors here. First, future emissions paths (and hence temperature rise) cannot, of course, be explained as simple linear extrapolations from the trend of previous decades. The relevant issue is the underlying forcing mechanisms; which we expect to rise at an increasing rate. As for logarithmic-vs-linear radiative forcing, here and here are good places to start.

      Your second-to-last paragraph gets to a core issue of climate change economics. The short answer to your question about why we should/do care about these issues is: The discount rate. Future net benefits (costs) are discounted over the full period so that they can be reflected in present value terms. Of course, this is the standard way of evaluating any multi-period flow of gains and losses; discounting provides a dispassionate tool for evaluating a highly emotive subject. (That said, debates over the discount rate itself are far from dispassionate. If you are interested in a further discussion, this post might interest you.) The broader point, however, is that these damages lower future growth relative to its baseline indefinitely into the future. This point is crucial to understanding why those future GDP losses matter, even if they appear small to you. On that note...

      Regarding your choice of phrasing: "if we could miraculously keep temperatures constant". To me, this indicates that you have fundamentally misunderstood the message in Tol's paper. Those are not the aims suggested by the likes of Nordhaus & co at all. For instance, here's Nordhaus (p. 14) laying out his "optimal" policy scenario:

      "Our estimate of the optimal emissions-reduction rate for CO2 relative to the baseline is 15 percent in the first policy period, increasing to 25 percent by 2050 and 45 percent by 2100. This path reduces CO2 concentrations, and the increase in global mean temperature relative to 1900 is reduced to 2.6°C for 2100 and 3.4°C for 2200"

      Does that sound like a policy that would cripple the present world economy? (For the record, I personally think that Nordhaus understates the negative impact of warming on future wealth. The previous link on the discount rate provides one reason related to his implicit assumption of perfect substitutability between man-made and environmental goods.)

      To finish, I don't understand your final comment. My statement was in relation to inertia of the carbon cycle and how our choices today will have no affect on the medium-term benefits that moderate warming is expected to bring (C.f. the "sunk" benefits described by Richard Tol in the post update.)

    4. *effect, not affect in the last paragraph.

      PS - Apologies if I come across as ornery in the above comment. I wrote it late last night after a long day. You do ask some important questions that anyone interested in this debate needs to grapple with. I hope that my answers provide some insight into why I hold the views that I do... as well as offer perspective on how economists evaluate the issues in climate change.

    5. Hi Stickman,

      "Why interesting?"

      Your use of the phrase "BAU" is interesting because the IPCC goes to great lengths to point out that they do *not* have a "BAU" scenario. In fact, they are emphatic that they don't estimate the probability of occurrence of any of their scenarios:

      "No judgment is offered in this Report as to the preference for any of the scenarios and they are not assigned probabilities of occurrence,..."

      IPCC brags about their unscientific approach

      This failure to assess the likelihood of particular scenarios allows people like you to make statements like, "Incidentally, we are currently on track with the A2 scenario, which is precisely what I have described as BAU..."

      As Michael Jackson would say, "No, no...that's just ignorant." (No offense intended, and with due respect. ;-))

      Seriously, there is no reason a person of your background (as far as I know of it) should have any idea why the A2 scenario is hilariously unrealistic. But ask anyone who has seriously studied energy and fuel trends, and they should be able to tell you why A2 is hilariously unrealistic.

      Here is a nice webpage of the IPCC emission scenarios. Go to the A2 flavors. For example, A2 ASF, The World. Take a close look, and see if you see anything ridiculous. If you don't see it, I'll tell you. (Or you could ask Jesse Ausubel. ;-))

      IPCC scenarios

      Best wishes,

    6. Hi Mark,

      Apologies for ignoring you; I'm simply snowed with work at the moment. However, I do mean to have a go at properly responding to all your questions when I get a chance.

      In the meantime, I've just clicked through to the IPCC scenario page that you provide above... specifically the A2-ASF-World link... And, yes, I would have to agree with your criticism that this cannot be described at "BAU" (even in the loose sense which I initially intended). For one thing, a population level of 15bn by 2100 is very much towards the upper probability tail of forecasts that I've seen. (I'd also have to take a closer look at that projected growth in coal use...) Mea culpa.

      I plead (unconvincingly):

      a) I initially put "BAU" in quotation marks, because it was meant to serve as a crude summary of scenarios where carbon emissions are left unregulated and economic growth remains fairly healthy.
      b) I had assumed population growth rates of the B2 and A2 families were the same after scanning a document before posting my comment. My mistake and you are right to call me out on this.

    7. Hi Stickman,

      "For one thing, a population level of 15bn by 2100 is very much towards the upper probability tail of forecasts that I've seen. (I'd also have to take a closer look at that projected growth in coal use...)"

      My reference was much more towards coal use. Converting the energy data in those Excel tables to coal use in billions of tonnes per year (using 29 GJ/Mg), scenario A2 averages 17 billion tonnes per year for 2010 to 2110, with a value in the year 2100 = 37 billion tonnes per year (the highest of any decade). Similarly, the A1F1 scenario averages 16 billion tonnes per year, with a peak value occurring in the year 2100, at 25 billion tonnes per year.

      But a simple check of Wikipedia indicates that total world provable reserves life is only 118 years at the 2010 production rate of 7.273 billion tonnes per year. In other words, over the next 100 years, the A2 scenario envisions the world using about *2.3 times* the world's proven recoverable reserves. And the production value in 2100 is *still increasing,* at over 5 times the current production.

      Wikipedia coal...see table on major producers

      It simply doesn't make any sense. It's like nobody at the IPCC has even heard of the concept of "Hubbert's Peak."

      Here's a paper by a group who has heard of the concept of Hubbert's Peak. They project global production peaking circa "30 percent above current production." See Figure 3, for example. They predict production of hard coal will be under 3,000 million tons in 2100. Compare that with the IPCC A2 scenario, in which coal production in the year 2100 will be 41,000 million metric tonnes (or 45,000 million tons).

      Energy Watch Group paper on future coal production

      It's just insane. The A2 and A1F1 scenarios simply do not seem credible. Carl Sagan popularized the great phrase: "Extraordinary claims require extraordinary evidence." It is truly an extraordinary claim that the A2 and A1F1 scenarios could possibly come to pass...that coal production in 2100 could be as much as 5 times current production and still rising. The IPCC provides no evidence (of which I'm aware) that their coal usage projections for these two scenarios are credible.

    8. [1/2]

      Hi Mark,

      On a study break, so let me reply quickly to some points.

      I hesitate to say this, but your calculations look a bit off to me... And I think you are missing an important distinction regarding proven reserves versus total resources.

      Just to be sure, can I first check that we're both using the same data as per above? If so, then let's consider the A2-ASF-World case again and, specifically, coal consumption...

      I've just run some conversions in the Excel file, using your rate of 29 GJ/metric tonne to ensure consistency. (For instance to find 2100 coal use in billion metric tonnes, I first take 904 EJ and multiply it by 10^9 to specify in term of GJ. I then divide by 29*10^9 to get in terms of billion tonnes, arriving at a figure 31.2.)

      Doing so for the whole series, I get the following projected consumption rates for every tenth year:
      2010: 3.6 bt (billion tonnes)
      2020: 4.5 bt
      2030: 6.3 bt
      2040: 8.2 bt
      2050: 10.1 bt
      2060: 14.3 bt
      2070: 18.5 bt
      2080: 22.7 bt
      2090: 26.9 bt
      2100: 31.2 bt
      "AVERAGE" (2010-2100): 12.8 BT

      It could be due to some rounding errors, but the fact that we get such different figures to begin with (e.g. 31 bt vs 37 bt for the year 2100) is perhaps not entirely trivial.

    9. [2/2]

      I have also put "average" in quotation marks because these are of course point estimates for a single year at the beginning of each decade; though we would not expect much difference if each year over the entire period was estimated separately. Indeed, if I calculate the implied growth rate for coal consumption over the 90 period, I get:

      3.6*(1+g)^90 = 31.2
      --> g = 2.41%

      Using this growth rate, we can integrate over the full 90-year period (see here) to arrive at a total consumption level of:

      INT 3.6*(1+0.0241)^t dt = 1,153 billion tonnes
      (Implying an average of 12.8 bt per year)

      Now, this total figure still exceeds -- by about 35% -- the estimated global coal reserves provided by the World Energy Council (WEC), which, as of their most recent report, stood at 860 billion tonnes.

      However, that does not mean that these estimates are irreconcilable or even unrealistic. Most importantly, as always with these things, definitions matter a lot. The WEC figure is "limited" to proven recoverable reserves which is very distinct from "resources". The definition of proven reserves is quite strict, which obviously means that estimated reserves will evolve over time. For instance, the coal reserves had increased by 13 billion tonnes from the WEC's 2007 survey to it's 2010 survey (see p. 3). This also underscores why R-P ratios -- though useful -- can be very misleading. They certainly change over time and not simply because of how consumption rates evolve. (This is one reason why I pay far less attention to "peak" theorists than I did a few years ago... the goalposts keep shifting.)

      Actually, here's a passage from the International Energy Agency (IAE's) World Energy Outlook 2011 (p. 402) that illustrates very well:

      "At the end of 2009, world coal reserves – the part of resources estimated to be economically exploitable with current technology (Box 11.3) – amounted to 1 trillion tonnes, equivalent to 150 years of global coal output in 2009 (BGR, 2010). [However,] total coal resources are many times greater. Globally, coal resources beneath land are estimated at around 21 trillion tonnes but, as market conditions change and technology advances, more coal will be “proven” over time."

      (If you can't access the WEO document, I can email it to you. There's also a nice discussion of the difference between reserves and resources on page 405.)

      So... under the A2 scenario that we are discussing here, the IPCC appears to be assuming that additional reserves are going to be found and will be economically recoverable... As per the above, many analysts would hold this to be a perfectly justifiable assumption.[*]

      Okay, enough from me. Back to studies!

      [*] Less important than the above... However, it's also possible that the IPCC are (implicitly) using a different conversion rate from joules to tonnes of coal (i.e. other than 29 GJ / mt). If you have time, it might be worth having a look through their documentation to check.

    10. Hi Stickman,

      Thanks for checking my numbers. I admit I get sloppy trying to get a point across. (Especially when I don't think the sloppiness will affect the point I'm trying to make.)

      I used 29 GJ/Mg from this site, I think:


      But I think I actually used 24-25 GJ/Mg.

      But let's try to get much more definitive. According the the A2-ASF spreadsheet, coal energy in 1990 was 92 EJ. According to this site, quoting EIA, there were 4,931,628 English tons of coal used in 1990. That would be 4,475,162 Mg.

      Indexmundi coal consumption

      That produces a value of 20.6 GJ/Gg.

      Using this IPCC site for 2005, I get 120 EJ coal energy:

      IPCC site

      Using the Indexmundi site again, I get coal usage for 2005 of 6,498,573 short tons, or 5,897,072 Mg.

      That gives me a value of 20.3 GJ/Mg.

      Average them both, I get 20.5 Gj/Mg.

      So that would change your numbers (which were based on my bad value of 29 Gj/Mg to):

      2010: 5.1 bt (billion tonnes)
      2020: 6.3 bt
      2030: 8.9 bt
      2040: 11.6 bt
      2050: 14.3 bt
      2060: 20.1 bt
      2070: 26.0 bt
      2080: 31.9 bt
      2090: 37.9 bt
      2100: 43.9 bt

      These numbers are of course even larger, so they're even more insane. I realize you don't think they are insane, but they are. You provided the WEO document that refers to what reserves theoretically exist. But that basically has nothing to do with what will actually be produced in the 21st century.

    11. Part 2...

      David Rutledge of Cal Tech has done interesting and good work on this subject. A Powerpoint presentation is here:

      David Rutledge Powerpoint

      Here's a paper:

      Rutledge coal paper

      From the abstract:

      "We show that where the estimates based on reserves can be
      tested in mature coal regions, they have been too high, and that more accurate estimates can be made by curve fits to the production history. These curve fits indicate that total world production, including past and future production, will be 680 Gt. The historical range for these fits made on an annual basis from 1995 to 2009 is 653 Gt to 749 Gt, 14% in percentage terms. The curve fits also indicate that 90% of the total production will have taken place by 2070. This gives the time scale for considering alternatives. This estimate for total production is somewhat less than the current reserves plus cumulative production, 1163 Gt, and very much less than the amount of coal that the UN Intergovernmental Panel on Climate Change, or IPCC, assumes is available for its scenarios."

      Here's an intesting piece from the Oil Drum website:

      Chinese coal monster running out of puff

      Note how, from 1965 to 2009, the rest of the world *except China* has only increased from about 1300 MToe (million tons of oil equivalent) to 1500 MToe. Do you *really* think the rest of the world is going to increase its coal production by like a factor of 6 in the next 88 years, when in the last 44 years it has only increased production by 15 *percent*? (Note: Production in the U.S. is down sharply since there may be essentially ZERO increase for the rest of the world in the 47 years from 1965 to 2012).

      Again, nobody who knows anything about the history of coal production thinks that the A2 and A1F1 scenarios for coal consumption are realistic. I've provided you the Energy Watch Group paper, the David Rutledge material, and the Oil Drum webpage. Here's another good one, by the way, that predicts "peak coal" in China:

      Peak coal in China

      You won't find anyone who says these people don't know what they're talking about, the the IPCC does with its A2 and A1F1 scenarios. If you think you've found someone who can dispute these people, send them here. I'll set them straight. ;-)

    12. What a mess!

      Couldn't even do that right. I multiplied your numbers by 29/20.6. I should have multiplied by 29/20.5. So the numbers are slightly larger...but in the third decimal place.

      Again, it doesn't change the fact that A2 and A1F1 are ridiculous. (And now I see A1C_AIM is ridiculous, too, based on David Rutledge pointing that out.)

  2. Hi "Stickman",

    I apologize if I came across as ornery in my comments. Any anger I have (which is could go to my blog to see some) is directed more at the IPCC than at anyone.

    IPCC's unfalsifiable "projections"

    I'll respond in more detail when time allows, but in the meantime, here's some potentially useful material regarding what I think about economics and climate change:

    21st century economic growth

    Implications of 21st century economic growth


  3. Hi,

    Some more comments, as I have time.

    1) "The relevant issue is the underlying forcing mechanisms; which we expect to rise at an increasing rate. As for logarithmic-vs-linear radiative forcing, here and here are good places to start."

    You may expect the "underlying forcing mechanisms to rise at an increasing rate." I don' least not throughout this century. First, you are almost certainly only considering CO2. Not methane, black carbon, HCFCs or CFCs. (And certainly not SO2...a cooling force that will be reduced in the near term, so lack of significantly increased warming will show that the SO2 cooling effect is overestimated...and therefore the CO2 warming effect is also overestimated.)

    Regarding the webpages you referenced: I essentially count as not very informed any page that says that CO2 will increase from 390 ppm to 780 ppm in the next 60-70 years. ("Wanna bet? I didn't think so.")

    But enough of engineering. Let's get to economics...and morality.

    2) "The broader point, however, is that these damages lower future growth relative to its baseline indefinitely into the future. This point is crucial to understanding why those future GDP losses matter, even if they appear small to you."

    I'm pretty sure by "indefinitely" you mean "forever." If so, I strongly disagree. That's why I asked you about GDP per capita in 2162. But even if the GDP losses *did* continue forever, I still don't see the morality of the relatively poor people of 2012 sacrificing for the much more wealthy and well-off people of 2100 and onward. That's why I asked you the questions about GDP and life expectancy in 2100. I realize I ask a lot of questions, but I would like to know your answers:

    "In 2012, the world per capita GDP is about $10,000 (PPP, 2012 dollars). What do you think the per capita GDP will be in 2095, PPP, 2012 dollars? The world-wide average life expectancy at birth in 2010 was 67 years. What do you think it will be in 2095?"


No anonymous comments please. (Pseudonyms are fine.)