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Further Comments on The Economist's Take on Climate Sensitivity

Posted on 11 April 2013 by dana1981

Last month, The Economist published an article about climate sensitivity – how much the planet's surface will warm in response to the increased greenhouse effect from a doubling of atmospheric CO2, including amplifying and dampening feedbacks.  We responded with some brief comments and critiques at the time.  Today two relevant and more in-depth articles on the subject were published, and are excerpted here.

How The Economist got it wrong

Dana Nuccitelli and Michael E Mann, ABC Environment, 12 Apr 2013


The expected range of climate change is around 3 degrees. This is based on several lines of evidence and other factors.

A recent news article suggested that climate change may not be as bad as feared. But the report was based on one flawed study and missed a lot of important points.

The Economist recently published a lengthy article about Earth's climate sensitivity — how much the planet's surface will warm in response to the increased greenhouse effect if the amount of carbon dioxide in the atmosphere doubles relative to pre-industrial levels (something that will happen in a matter of decades if we continue with business-as-usual fossil fuel burning).

While we are pleased that The Economist brought attention to this important topic, we were disappointed by the shortcomings and inaccuracies in the piece with regard to the current state of scientific understanding.

The article focused heavily on claims that the slowed warming of Earth's surface in recent years implies a dramatically lowered estimate of climate sensitivity. The claim was primarily supported by a single as-yet unpublished article by a group in Norway, which attempts to use instrumental temperature evidence available back through the late 19th century to estimate the climate sensitivity. The authors of that article conclude that use of data to the year 2000 yields a climate sensitivity of 3.9°C, which is at the high end of the generally accepted 2 to 4.5°C range. Yet they find that by including just an additional decade of data (i.e. using observations available through 2010), the estimate falls by nearly half, to 1.9°C.

It should be a red flag that an estimate of climate sensitivity would change by a factor of two based only on the addition of a decade of data. In reality, the climate sensitivity now is not half what it was a decade ago. So where did the Norwegian study go wrong?

Click here to read the rest of the story at ABC Environment.

Think the Planet Isn't Warming? Check the Ocean


A recent article in The Economist stated that “over the past 15 years air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar.” The Economist went to great lengths to point out that “the mismatch between rising greenhouse-gas emissions and not-rising temperatures … does not mean global warming is a delusion.” But the piece was predictably lauded by climate skeptics as “further evidence” of the case against climate change.

Except that … it wasn’t.

As The Economist piece itself pointed out, this wasn’t an argument that “global warming has ‘stopped.‘” The past two decades have been the hottest in recorded history; of the nine hottest years on record, eight have come since 2000. The question, though, is why the year-on-year/decade-on-decade increase appears to have been somewhat less in the past 10 to 15 years, given the ongoing increase in atmospheric greenhouse gas concentrations.

To which there are several answers.

Click here to read the rest of the story at Discovery News.

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Comments 1 to 38:

  1. So you would just wish the economist would chip in with comment on how we could achieve green house gas reduction within the economy rather than question the science.

    I don't think they have contributed to the economics of meeting the 2c. Rather they want to rant on about the science. Its the sort of denial we find in the general populous. Avoid avoid avoid.... Put off.

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  2. Paul Magnus and Authors

    As a long time subscriber to the Economist, I have found their information on a range of subjects to be well researched and first class.  It is a 'newspaper' widely read amongst decision makers all over the world.  Their science and technology section is written for the layman but well detailed and cutting edge in many fields.

    I would not dismiss their subject article on climate change as a sort of denialist rant.  

    The Discovery News rebuttal story you quote above is unimpressive in detail and would have much less authority than the Economist story.  

    The Economist is not denying a contribution to global warming by CO2 means but the authors make a good case that the extent of warming has probably been overstated, and the uncertainties probably understated.

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  3. Archie, if the article were well-researched, you'd expect the message to be in line with 'cutting edge' climate science.

    It isn't.

    Therefore, either it was poor research, if you give the economist the benefit of the doubt, or wilful ignorance (denialism).

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  4. archie @2 - we did not dismiss The Economist article "as a sort of denialist rant."  We simply pointed out all the important research they did not include.  Failing to include that research skewed the article towards a conclusion that is not well supported when all evidence is considered.

    Your final paragraph misses the point.  They make a good case that the extent of warming has probably been overstated?  That's like saying climate contrarians make a good case that the surface temperature record is biased.  As long as you only consider the evidence and research that supports your conclusion, it's easy to "make a good case".  Until you account for the contradictory evidence.  That was the point of our article.

    The Economist is a good magazine and usually writes good climate pieces.  This one was not very good.  I'm not accusing them of being deniers, just pointing out that they made mistakes in this article, which led to a wrong conclusion.

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  5. archie lever, the only way I can make sense of your contention that the Discovery News rebuttal story is "unimpressive in detail" and "would have much less authority than the Economist story," is to assume that you failed to click on the hyperlinks in the Discovery News story.

    Print media must list their references as immediately-viewable text. That is distracting, so footnotes and endnotes were invented to reduce interference with reading the primary material while still providing easy access to the supplementary details.  But electronic media often eliminate the distraction of the footnote and endnote numbers embedded in the primary text, by making key words and phrases links to that supplementary material.

    In both that Discovery News story and the ABC Environment story, please click the embedded links to get to the details that you thought were not provided.

    Here on the Skeptical Science site, most "Argument" rebuttals have multiple levels of detail contained in multiple tabbed panes: Basic, Intermediate, Advanced.  The Argument Rebuttals are the ones in the "Most Used Climate Myths" list at the top left of every page, plus a much fuller list you can access by clicking the "View All Arguments" link there or the "Arguments" link at the left of the blue horizontal bar at the top of every page.  (The Argument Rebuttals differ from the regular "Posts" such as the one you are reading now.)

    I suggest you get a quick orientation to the science of climate change, by visiting the Home Page of this Skeptical Science site, and clicking the three big buttons at the top of that page: "Newcomers, Start Here," "History of Climate Science," and "The Big Picture."  Remember that in all those pages, the details are accessible simply by clicking the hyperlinked in-line text.  To get an accurate impression of how much detail really does exist, then visit The New Abridged Skeptical Science Quick Reference Guide.

    You can keep an eye on comments across all the threads by monitoring the Comments page, which you can access by clicking the Comments link in the middle of the horizontal blue bar at the top of every page.

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  6. Just a little point. I've heard the response from some of those in climate denial that if the heat is going into the oceans then that's a good thing; as if it's lost forever. I think it's important to reiterate what seems obvious to anyone who understands the basics of climate change: heat into the oceans is heat into the overall climate system and it will eventually come back to bite us.      

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  7. John R:

    Kind of like the accident victim that is bleeding internally, with no visible signs of bruising or blood loss (yet), who is about to collapse and die?

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  8. dana 1981

    This quote is the central issue posed by the Economist article.

    "Temperatures fluctuate over short periods, but this lack of new warming is a surprise. Ed Hawkins, of the University of Reading, in Britain, points out that surface temperatures since 2005 are already at the low end of the range of projections derived from 20 climate models (see chart 1). If they remain flat, they will fall outside the models’ range within a few years.

    The mismatch between rising greenhouse-gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now. It does not mean global warming is a delusion. Flat though they are, temperatures in the first decade of the 21st century remain almost 1°C above their level in the first decade of the 20th. But the puzzle does need explaining.

    The mismatch might mean that—for some unexplained reason—there has been a temporary lag between more carbon dioxide and higher temperatures in 2000-10. Or it might be that the 1990s, when temperatures were rising fast, was the anomalous period. Or, as an increasing body of research is suggesting, it may be that the climate is responding to higher concentrations of carbon dioxide in ways that had not been properly understood before. This possibility, if true, could have profound significance both for climate science and for environmental and social policy."Falling off the scale

    If the actual global mean temperature is exiting the 5-95% confidence level of the climate models - clearly there is something wrong with the models.  This has not been effectively addressed in any of the comments seen here of the Discovery News article or links.

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  9. Archie, we generally expect about 10% of the data to fall outside the 5-95% CI. That's kind of what a 90% CI means.

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  10. Archie said

    "The mismatch between rising greenhouse-gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now."

    Er ... not rising temperatures? Are you referring to global temperatures, or land surface temperatures? Globally, the oceans have been warming at the expected rate. Land surface temperatures have been constrained by such influences as ENSO and have behaved as expected, given the forcings. Which part of this is a big puzzle?

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  11. And Archie, global ice mass loss has accelerated during the Had4 surface temp "hiatus."  Remember: the climate-scale global (plus poles) surface trend is .169C per decade, just a hair short of the expected rate of warming.  Use the eyecrometer and end up standing in the foolish line.

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  12. Interestingly the UK Met office has just released a statement on cold winters that is completely at odds with its previous comments on the effects of global wrming on the UK climate.  Sometimes, like Archie Lever I find it difficult to determine what the real situation is.

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  13. If climate sensitivity hasn't fallen by a factor of 2, what would some of you suggest as a respectable amount of 'fallen off', and what percentage of certainty would that lay at?

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  14. Climate4All - please tell me how you can get OHC values at current levels with a sensitivity of 1.5.

    For those of you here that think current surface temperature trends suggest climate models are wrong, can I ask which of these you believe?

    1/ The next El Nino of greater than 1.8 wont break surface temperature records.

    2/Models should be able predict the ENSO patterns

    3/ Eli Nino's will be rare in the future and La Nina/Neutral conditions will surface temperatures as they are.

    Ray, Climate4All, Archie?

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  15. I think we are encountering a problem I find frequently in my work with financial modelling. These models are less complex than the climate models, but their use generates similar arguments about interpretation of actual results versus those expected from the models. The simple problem is that the vast bulk of consumers of model outputs (climate and financial) have a very limited appreciation of stochastic type outcomes.

    One can talk all one likes about 90% CIs and that 5% of actual outcomes will fall above and 5% below, but the users still get twitchy when the actuals are not tracking near the median line. The reaction in my experience is ALWAYS that there must be something wrong with the model and if the 90% CI line is broken the general view will be that the model is definitely and clearly wrong and must be fixed. 

    This inherent difficulty of understanding is coupled with the fact that the majority of the presentation of climate warming to date has demonstrated the effects using surface temperatures. Surface termperatures, after all, are what people, plants and animals actually experience.

    I started studying climate impacts and models back in the 1970's and have no doubts about the veracity of the current science or its predictions (naturally within the normal scientific error bars). The current results are falling close to the 90%CI boundary because of the correlations of effects that hold surface temperatures lower over recent years versus the correlation of effects that held them higher 15 years ago. The actuals have not broken the boundary in the timeframe on the chart above which covers nearly 100 years and we would have expected a few by now so the models are clearly doing a very good job and I, for one, am quite comfortable with the estimated sensitivity. It looks absolutely spot on (within error bars).

    But expect serious confusion and complaint against the models if the actuals actually do breach the 90%CI. The problem of course is much much wider than surface temperatures so we better start educating as even some of the comments on this forum demonstrate.

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  16. @14 scaddenp

    The contention that I address only are those that Dana and Micheal suggest.

    Not the OHC values. Not El Nino and its relationship to to surface temperatures. Not models being able to predict ENSO patterns, though I do believe that some models adjust  for a general weakening of it.

    Dana is willing to say they got it wrong, but by how much and at what certainty should global temperatures reside. he didnt say they got it completely wrong. 

    Has Mann done a similar study for the last decade yet? 

    I just wanted clarification.


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  17. Climate4All - climate models have no skill at decadal prediction. They have never pretended to. That is pretty much the point made - and the problem with the methods that dont take account of high surface temperature variability.

    First I have heard that model predict weakening of it. Got a source for that?

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  18. Ray at #12  Re; apparently conflicting comments about weather from the UK Met Office.

    One of the problems is that although we can know with high levels of certainty that the world is warming, and by how much per decade, it's very difficult to predict the effects of that warming on the resultant weather in a particular country -- particularly one as prone to variable weather as the UK. That's because we've never seen rapid rises in global temperature before during any periods when humanity has been in a position to record the results. 

    The truth is that a few years back the Met Office were more confident as to how global warming would manifest itself on UK weather than they are today. That's why, for instance, they dropped the long-range weather forecast. We've entered unchartered territory now and the changing pattern of the jet stream that has become apparent over the last few years is one example of the sort of change we're seeing.

    As climate scientists have started to realise how much they don't know about the way global warming will manifest itself on weather, you've seen the Met Office change from statements like "expect warmer winters with less snow" (the simplistic guess) to the uncertainty revealed by the statement by Julia Slingo who said about the current cold weather the other day, "if this is how how climate change could manifest itself, then we need to understand that as a matter of urgency".  

    I think that instead of looking at this a weakness you need to put it in the context of the huge scientific research effort to understand what global warming will mean to weather. 

    If you'll permit me to use an analogy. It's like the uncertainty of a hot air balloon flight. If we know the direction of the wind, the amount of weight on board and how much gas it carries, we can predict with a reasonable level of certainty in roughly what area it will land. The more information we have and the more experienced the pilot, the surer we can be of predicting the landing site.  But there are always variables and at the moment things are happening that create uncertainties we have not experienced before. This is making predictions more difficult; but everyone is working very hard to understand those uncertainties.  Don't lose sight of the fact that however much uncertainty there is there is, one thing is not in question: the ballon will come down somewhere. 

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  19. Fresh from accusations of being a "SkepticalScience affiliate" by denialistas amongst The Economist commenters, I finally arrive here courtesy of a comment on my own blog. Would anyone here like to play "Spot the difference!" and then "What if?"?

    Re #12 and #18, here's the latest news from the sharp end over here in soggy South West England, just down the road from the Hadley Centre:

    To summarise, it seems Julia Slingo disagrees with The Economist leader writer. However it's still not clear what she intends to do about it.

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  20. Doug Hutcheson and others

    The Economist leader writer said that - not me.

    He/she also said that:

    "OVER the past 15 years air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar. The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASA’s Goddard Institute for Space Studies, observes, “the five-year mean global temperature has been flat for a decade.”

    I assume that by global temperature the authors mean the composite sea and land temperature, but you would probebly have to confirm than with Jim hansen and Ed Hawkins.

    (-off topic snipped-).  

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    Moderator Response:

    [DB] Please take further discussion of models to the "models are unreliable" thread.  Models are off-topic on this thread.

  21. (-moderation complaints snipped-).

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    Moderator Response:

    [DB] Models are off-topic on this thread, as previously noted.  This applies to all parties, equally.

    [TD] Archie, nearly everything on this topic is related to everything else, so it would be easy for every post and comment thread to end up being about everything.  One of the strengths of this site is the collection of related ideas together. That makes them easy to find.  It also reduces redundancy across threads.  And often people discover that they change what they want to write after reading the original post and some of the other comments in the most immediately relevant thread.

  22. archie @8 - this is not right:

    "If the actual global mean temperature is exiting the 5-95% confidence level of the climate models - clearly there is something wrong with the models. "

    First of all, I don't know what "exiting" means here.  That assumes we know what will happen in the near future, which nobody does.  Second, as pointed out by Tsumetai @9, we expect the data to fall outside the 5-95% confidence interval 10% of the time (below it 5% of the time).

    In short, what's happening is that the model runs that simulate the lagest cooling effect on surface temps from natural variability are right.  Then you have to compare the current observational data to the model runs and see if that makes sense.  So what's happening in the real world?  We're seeing a preponderance of La Niña events, an accelerated warming of the oceans, especially the deep oceans, low solar activity, etc.  Basically what we would expect for a period of relatively flat surface temps - the heat is going elsewhere.

    If there's anything 'wrong' with the models, it would be that they don't accurately reflect the magnitude of natural variability associated with the transfer of heat to the oceans, but since the observations are still within the range of model simulations, that's not an accurate statement.

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  23. Climate4All @13 - equilibrium climate sensitivity (which the Norwegian study is attempting to estimate) should be an essentially constant value.  It shouldn't fall or increase by any significant amount just by adding in another decade's worth of data.  If it does, as with the Norwegian study, then you know something is wrong with the model (i.e. it's too sensitive to short-term natural variability, and not accounting for some important factor[s]).

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  24. It is unfortunate that people (some who should even know better), continue to misrepresent and misinterpret Ed Hawkins' graphic.  Ed Hawkins recently posted a figure that specifically deals with the misinterpretations.


    Referring to the above figure, Hawkins concludes that [my edit for clarity]:

    "This demonstrates that a slowdown in [surface] warming is not inconsistent with future projections." 

    As another example of Ed' warning. Look at The Economist figure carefully. Circa 1975 the observed global temperature dropped (temporarily) below the confidence interval of the model simulations. Now applying the current logic of responses to the slowdown in global surface temperatures, back then fake skeptics at the time would have no doubt been loudly claiming that the models were "useless", or perhaps claiming that it was evidence that climate sensitivity was low/er, or evidence that global warming was a non issue. They would have been wrong, global temperatures have increased about 0.6 C since then.

    So similar arguments being made today are almost certainly going to be wrong.

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  25. scaddenp

    Hopefully the Moderator will permit this post but as your post asking the questions was permitted I would imagine that my responses to those questions will also be permitted.  However I don't wish to be too sanguine as that would be presumptuous.


    1/ The next El Nino of greater than 1.8 wont break surface temperature records.

    No idea.  Here's a couple of comments that suggest the answer to your question might be less straightforward than it appears. El Niño is not the only effect on weather as it is just one fluctuation among many, and the weather is the sum of all of these overlaid and interacting. Most of these interactions are poorly understood, particularly the longer-term ones, and as we get longer and longer records we become aware of more and more complexity. This from Scientific American "The results show that the variability and strength of the ENSO cycle was greater during the 20th century than at most points in the 7,000-year fossil record -- but the episode is not unprecedented, the scientists said, pointing to a similar period during the early 17th century."  This variability probably precludes a definitive answer to your question

    2/Models should be able predict the ENSO patterns

    Your question really isn't phrased correctly.  The answer to the question you ask is "Yes they should be able to.  A more pertinent question is perhaps is "are they able to predict the ENSO patterns".   The answer to that question  is that so far the predictive results are variable as the observational results showed the 1997 El Nino was occurring before the models predicted it.  The US Global Change Research Information Office has suggested a possible reason for this predictive failure is the  Madden -Julian effect which was not considered by models.They go on to say "At present, no forecast system captures intraseasonal signals such as the Madden-Julian oscillation with any skill. Once again, a target exists for improved models".  This seems to answer the revised question.

    3/ Eli Nino's will be rare in the future and La Nina/Neutral conditions will surface temperatures as they are.

    This question doesn't make sense

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  26. Ray,
    " El Niño is not the only effect on weather". It is a given that volcanoes and solar are part of the surface temperature variability, however, ESNO is the major effect. There may be other factors at work, but at present there is little evidence for them. See Foster and Rahmdorf 2011 and Rypdal 2012 These studies do not rule out other factors, but also show that no other factor is necessary to explain most of the month by month variability. Comments should go to here. I cant check your SA reference (please give proper links) but its makes the point that ESNO is unpredictable. However, given an index of 1.8 or more, evidence so far point that producing a record unless it was also accompanied by a major low latitude volcano.

    2/ "Your question really isn't phrased correctly". Oh yes, it is. Given the above point about the dominance of ENSO in variability, complaining that model predictions about current surface temperatures is wrong implies models should be predicting ENSO. As you correctly state, they cannot. However, OHC, ice, sealevel all point to earth system continuing to accumulate energy and so that will be expressed in the surface temperatures eventually.

    3/ "This question doesn't make sense". Okay, that should have been better stated. The current ENSO pattern isnt particularly unusual historically and can be expected to deliver periods of El Nino dominance in future. Guess what happens to surface temperatures then? If you wish to believe that continued accumulations of GHGs dont matter and warming wont return, then you also somehow need to believe that El Nino's . 

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  27. dana1981

    I was making a general point about the Economist article from a newspaper which is influential worldwide, as is Skeptical Science. Hence my visit to your site - you are quoted outside this blog as a source of reference material on climate science.

    I think it would be fair to say that the Economist's researchers have a standard to maintain, and that serious errors in their 2 page article would be unlikely. Their conclusions say to a pretty well educated readership that the science is not settled and the projections of warming might well be exaggerated.

    Now regarding your specific points, you say:

    "So what's happening in the real world? We're seeing a preponderance of La Niña events, an accelerated warming of the oceans, especially the deep oceans, low solar activity, etc. Basically what we would expect for a period of relatively flat surface temps - the heat is going elsewhere."

    As Ray@25 has pointed out, ENSO patterns and other effects are poorly understood, and I don't think anyone can claim definitive knowledge of the energy uptake in the deep oceans. Low solar activity is on an approx 11 year cycle so the last 10-12 years should have seen all phases of one cycle. Computer predictions going forward are used by climate scientists to warn the public and policy makers all the time. It is their most powerful tool for sending the message.

    I think it is obvious that the actual global temperatures from Ed Hawkins Chart 1 are heading outside the 5-95% confidence interval after a 10-12 flat period - something not seen since the 1950-1980 period, given that all the effects of CO2 release, ENSO, solar cycles, ocean absorption should be present in the Ed Hawkins 1950- chart.

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  28. archie lever,

    In your comments above you have stressed that you consider the Economist to be a reliable source of information (its influence, is of course, irrelevant to this discussion). Further to this you have criticised climate scientists such as Michael Mann for pointing out errors in its article about climate science.

    How then, do you propose the standard of journalism on the Economist should be judged ? Your position appears to be that it should not, or at least it should not be judged by those most qualified to do so.

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  29. archie, it's odd that you seem to be sticking by the reporters' opinions in that Economist article, despite the clear evidence contrary to their opinions--the evidence you see here on Skeptical Science, and the evidence in the other sources that have been linked in the comments section of the Economist article.  You seem to be relying entirely on the "reputation" of The Economist, ignoring the concrete, detailed evidence you can see for yourself here and elsewhere.  My guess is that you do not understand how reporting about science differs from reporting about many other topics such as the business topics that The Economist more often covers.  In science, the primary sources of information are the peer reviewed scientific articles, which are publicly available.  People can argue over their interpretations of those articles, but for a contrary opinion to be taken seriously it needs to be expressed in another peer reviewed publication.  Opinions by Skeptical Science authors don't mean much unless they are vetted by peer review, such as has happened for example in Cawley (2011) and Nuccitelli et al. (2012).  For that reason, Skeptical Science posts always cite the peer reviewed scientific publications they are interpreting, and even provide links to them for your convenience.  You don't have to take the science reporters' interpretations at face value, because you can read the sources yourself.

    That differs from many other types of reporting, in which the primary source of the information either is available only in paper inside a particular office of a particular company or agency, or was uniquely accessible as a private interview of a source person by a reporter.

    Climate change is a scientific topic.  You have been presented with a wealth of the evidence, clearly explained with easily accessible primary scientific sources.  Please use all that.

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  30. I realise that this comment is not strictly related to the article, and would understand if it is not approved.

    I recently read the article "The Joy of Global Warming" in the News Review of the Sunday Times (printed 31 March 2013).  The synopsis at the start read "Climate change can be good for us and we are wasting billions trying to fight it before we need to".  Have you at Skeptical Science read this article, and are there any plans to respond to it?  If it is misleading or inaccurate, I would be happy to register a complaint about it via the UK Press Complaints Commission.

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  31. This discussion of the finer point of the future temperature are interesting but in reallity farming as we know it stops at 3C and many major cities go underwater at 1 meter. It is also a gradient of disaster so that we will be under a lot of stress leading up to that. my web site tries to alert people in NZ to the problems in many areas.

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  32. Climate Bob @31, while it is largely true that New Orleans goes underwater at 1 meter of sea level rise, for most coastal cities a 1 meter sea level rise inundates only a small faction of their area.  In Australia's case, it is estimated that $300 billion dollars worth of property would be innundated by an approximately 1 meter sea level rise (actually 1.1 meter).  That sounds like a lot, until put into context by Australia's US$ 1.37 trillion economy.  In context, however, it is seen that a sea level rise of 1.1 meters  will inundate 4.6% of Australia's GDP in property, over a period of 50 to 100 years.  The annualized cost would be a minor drain on Australia's budget at most.

    There are some regions where the effects of sea level rise are far greater, notably the Nile Delta and the Ganges Delta (aka Bangladesh).  The tragedy in those cases will not, however, be in the net cost of sea level rise as a portion of the world's economy (which will be small) but that Egypt and Bangladesh will be left carying the massive costs in national terms without significant assistance.  Sea level rise raises serious issues about justice, but few about economics.

    However, overstating the case ("many major cities go underwater") is not helpfull.  Nor does overstating the case on agriculture, which will not "cease" at 3 degees C, although it may be severely limited and is a far greater concern than sea level rise.   A 10% reduction in land area for cities is hardly consequential given the total land area of the Earth.  A 10% reduction in agricultural yield may be truly catastrophic, especially given increasing populations.  But equating such uncertain reductions with "agriculture ceas[ing]" is absurd.

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  33. I think it is useful to consider what infrastructure will be rendered unserviceable by sea level rise.

    Ports, of course, will be affected, impacting upon international trade. Many cities are in existence because they are trade centres, meaning that much of their infrastructure is low lying. Coastal airports around the world are often just above sea level, for example. So also are many heavy industries, power generation facilities (including nuclear: cf Fukashima), chemical plants, oil refineries and so forth. Then there are the road and rail links which service such sites.

    Altogether, the amount of land surface lost to SLR is important, but the dislocations to economies, due to the existing uses of such land, could be critical. It would seem we need to start relocating our centres of human activity above the new high tide line, well before they are placed at risk.

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  34. Isn't it likely to be more cost effective to build sea walls than move things?

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  35. Tom Dayton @29

    The Economist's authors quote several 'peer reviewed' sources in relation to climate sensitivity and other factors affecting global temperatures.  Again it comes down to a matter of opinion as to whose source will be proven more accurate in the future.

    The article clearly says that the weight of recent evidence has moved the centre of gravity for equilibrium sensitivity (assumed 3 degree celcius up until now) closer to 2 degrees celcius or lower.  This implies that forcings affected by clouds, water vapour feedbacks,  ENSO, ocean heat absorption are not as well known as supposed in current modelling and hence the divergence over the last 10-12 years.

    It also implies that policy makers have more time to reduce CO2 emissions and move to cleaner energy sources.

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  36. Tristan @ 34, building sea walls only works to a limited extent.

    Firstly, one needs to know how high to build them, secondly there are logistical problems about where to build them and, thirdly, one needs to take cognisance of the underlying geological structures, to be sure water cannot penetrate beneath them (I understand much of Florida is not suitable for protection by sea walls, for this reason).

    The first consideration is the most important: how high does one need to build a sea wall, to ensure it is high enough to cope with the maximum possible seal level rise and that it is not liable to being overtopped by a storm surge?

    Sea walls do not work in delta environments like Bangladesh and do not help infrastructure that relies upon being close to, but above, sea level. Such items as ports and industries relying upon seawater for cooling come to mind.

    This discussion is going off-topic, so I suggest you continue on a more appropriate thread.

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  37. Thanks Doug.

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  38. The Economist has now published some letters from their readers on their original article.

    They lead with "current climate-change policy is an expensive waste of time" and relegate "Quantum physics and thermodynamics... yield a baseline climate sensitivity of about 3°C" to second place.

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