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How climate skeptics mislead

Posted on 13 June 2010 by John Cook

In science, the only thing better than measurements made in the real world are multiple sets of measurements – all pointing to the same answer. That’s what we find with climate change. The case for human caused global warming is based on many independent lines of evidence. Our understanding of climate comes from considering all this evidence. In contrast, global warming skepticism focuses on narrow pieces of the puzzle while neglecting the full picture.

What is the full picture? Humans are emitting around 30 billion tonnes of carbon dioxide into the air every year. This is leaving a distinct human fingerprint:

Signs of warming are found all over the globe (here are just a few):

On the question of human caused global warming, there’s not just a consensus of scientists – there’s a consensus of evidence. In the face of an overwhelming body of evidence, the most common approach of climate skepticism is to focus on narrow pieces of data while neglecting the full picture.

Let's look at an example. One popular skeptic argument has been to cast doubt on the surface temperature record. Skeptics claim thermometers are unreliable because surroundings can influence the reading. They reinforce this by showing photo after photo of weather stations positioned near warming influences like air conditioners, barbeques and carparks. The Skeptics Handbook goes so far as to say "the main 'cause' of global warming is air conditioners".

This myopic approach fails to recognise that air conditioners aren't melting the ice sheets. Carparks aren't causing the sea levels to rise and glaciers to retreat. The thousands of biological changes being observed all over the world aren't happening because someone placed a weather station near an air conditioner. When you step back and survey the full array of evidence, you see inescapable evidence of warming happening throughout our planet.

Our understanding of climate doesn't come from a single line of evidence. We use multiple sets of measurements, using independent methods, to further our understanding. Satellites find similar temperature trends to thermometer measurements. This is despite the fact that no carpark or barbeque has ever been found in space. Prominent skeptic Roy Spencer (head of the team that collects the satellite data) concluded about the HadCRUT surface record:

“Frankly our data set agrees with his, so unless we are all making the same mistake we’re not likely to find out anything new from the data anyway"

Our climate is changing and we are a major cause through our emissions of greenhouse gases. Considering all the facts about climate change is essential for us to understand the world around us, and to make informed decisions about the future.

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Comments 1 to 50 out of 229:

  1. This article is good, but I think it misses at least one important point. True, other lines of evidence do support global warming, but scientists did themselves and the world a disservice by such sloppy methods for gathering surface temperature data. The sarcastic rejoinder "global warming is caused by air conditioning", is all too potent a tool for a political PR slogan.

    Remember: science alone cannot stop global warming. Radical political action is needed as well. Such action will happen: the question is whether it will happen now, with little bloodshed, or later, with massive bloodshed and loss of life due to emerging diseases and vanishing habitat.
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  2. John,

    It is a good idea that you keep recycling this theme lest some get lost in the straws.

    I keep stating that there are three conclusions:

    1) An overwhelming majority of international climate experts agree about much of the tenets of AGW and are honest.

    2) An overwhelming majority of international climate experts are ignorant about their own expertise in a sudden and collective manner. (Claims of group think included.)

    3) These scientists have all agreed to conspire to delude the billions of folks on the planet and just a very tiny percentage of them (and mostly oil-funded and unpublished) are trying to save us all from this mass hoax.

    Common sense and a sense of probability should lead one to the likely correct choice above.


    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    My Global Warming Blog
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  3. neglecting the full picture

    Scientific approach is not about pictures and it is definitely not holistic. Whenever pieces of the full picture don't withstand analytic scrutiny, those pieces should be abandoned, even if they seem to be consistent with multiple lines of evidence. This is the nature of the scientific method.

    Techniques suggested by the way people contemplate on Rorschach figures may be indispensable heuristic tools, but as soon as a hypothesis is formed, one should switch from vision to cold logic.

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  4. I like E. O. Wilson's term consilience. Evidence converges towards one conclusion from a wide variety of directions. Any given line (every line) has some possibilities for error. But those possibilities and routes of error are different between the different lines. There is consilience between lines of evidence as wildly different as sea level, global thermometer networks, and the times of flowers blooming in the spring. (And many, many, more.) They all have sources of error, but each source of error could as easily point to cooling as warming. Yet there is consilience that the earth is warming.

    mattj: I haven't read a lot of the 19th century literature about collecting surface air temperatures and sea surface temperatures, but some. I think it's quite a stretch to condemn people 100 years ago for not having collected their data in ways that we in 2010 wish they would have. If you read their work, they were clearly trying to collect the best possible observations, in the best possible way, as they understood it at the time, and for the purposes they were collecting the data at the time. 30, 70, 130 years later, we're trying to do different things with the data, in different ways. That's our problem. Calling them 'sloppy' for not anticipating our interests and methods doesn't strike me as fair to anybody, or useful for anything.
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  5. John Cook says:

    "Skeptics claim thermometers are unreliable because surroundings can influence the reading. They reinforce this by showing photo after photo of weather stations positioned near warming influences like air conditioners, barbeques and carparks. The Skeptics Handbook goes so far as to say "the main 'cause' of global warming is air conditioners"."

    I remember in grade school seeing a wall unit air conditioner running full blast on a hot summer day with a shimmering appearance right outside the window that gave the impression of something rising up right from behind the A/C. That was the hot air exhaust.

    The fact is that hot air rises immediately, not after it travels 20 or more feet horizontally to swirl around the thermometer.
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  6. It is hard to worry much about "sloppy" surface data weather collection when we see results like this:

    http://www.skepticalscience.com/Is-the-US-Surface-Temperature-Record-Reliable.html

    Quote: "The work of surfacestations.org is useful in clarifying one point - microsite influence has imparted little to no warming bias in the U.S. temperature record."
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  7. Keep up the good work. You're doing a great service.


    By the way, another common method (this is not news, I'm sure) by which climate skeptics mislead is by bluffing credentials and experience. It is as effective as twisting facts, but safer, because they are rarely challenged. People are too busy and too aware of their own lack of science training to find out things. It is usually fairly effective to believe an expert. So, self-appointed climate rebels who feel that AGW is all a hoax spend a fair bit of their argument with falsehoods about their own positions as "renowned" scientists, the smartest and the first, etc., when the opposite is usually true. The British have a good word for it: puffery. A complete nobody in climate science can look into the TV camera and say "I am one of the few people qualified to speak about climate change", and people believe the next malarkey that comes out of his mouth. Amazing. The deniers get away with arguing from (falsely attributed) authority because the future of the planet is not important enough for the rest of us to challenge personal claims. That could be embarrassing.
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  8. This is an excellent post because it is both clear and succinct.
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  9. @ Dan (post #7). I think This video really highlights the point you're making about people padding their resumes to make themselves sound more credible on this issue. Like the guy says (ok, so I'm paraphrasing here)-"would you go see a GP to get brain surgery done? NO-then why do we trust weathermen or Classics Graduates for their OPINIONS on climate change?"
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  10. #6 Dan at 10:04 AM on 13 June, 2010
    It is hard to worry much about "sloppy" surface data

    No, it is not hard. Just criticism is largely misplaced.



    The Global Average Urban Heat Island Effect in 2000 Estimated from Station Temperatures and Population Density Data
    by Roy W. Spencer, Ph. D.

    You can see, as UHI is roughly proportional to the logarithm of population density, the problem gets really serious only with stations in the least densely populated areas.

    UHI effect is roughly logarithmic with

    ΔT = 0.23×log(0.66×d)

    where d is local population density per km2.

    As global population density between 1900 and 2008 has increased fourfold, in first approximation this effect alone can explain about a 0.23×log(4) ~ 0.32°C increase in global average surface temperature during this period as measured by meteorological stations.

    However, as relative abundance of stations flagged rural in GHCN has increased recently, the actual figure must be higher (because at low population density the curve is steeper).

    Not much warming is left.
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  11. "Not much warming is left. " Phew, there's a relief. But how do I explain that to the glaciers?
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  12. #11 David Horton at 11:26 AM on 13 June, 2010
    how do I explain that to the glaciers?

    No need to explain them, they are not sentient. Just filter out soot from smoke.
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  13. Actually air conditioners do at least contribute to global warming, as most of them are in the US and they suck up untold Megawatts of electric power , which in turn is mainly generated by coalfired powerstations. :)
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  14. That's more or less my general argument; that there are so many lines of evidence and impacts that the argument of AGW is pointless, meaningless and provokes inaction in the face of so many issues.
    One thing that I'd like to say, however; I wouldn't say that "species are becoming extinct". More accurate would be to say that current extinction rates are being further exaggerated by climate change. We know that our land change use is already having a massive impact on biodiversity, but with climate change impacting on distribution (tending to shift further from the equator) and ecological cues (ie. first bloom, nesting etc), this is having a detrimental effect on species and community fitness. Then acidification of surface waters...
    These are happening, regardless of the first comment here "not much warming is left" of which I'm happy to provide a list of papers.
    Cheers,
    Tim
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  15. Berényi Péter: How much has the population grown over the oceans? Must be a lot of UHI there because T trends over those regions are pretty close to those over land.

    Why does this dead horse keeping trying to get up?

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    My Global Warming Blog
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  16. Your argument still misses the point.

    Skeptics are primarily concerned about exageration.

    Even the more extreme skeptics concede that c02 causes warming, the question is how much (negative /positive feedbacks), and that necessarily means exageration on various levels is a key issue. They key quesiton is overall climate sensitivity, and urban surface temperatures, for example, are being used to bolster up higher climate sensitivity estimates and formulate policy. Urban heat islands are not melting glaciers, but skeptics contend that glaciers are melting largely naturally, and superficially enhanced urban surface temperatures are being used to falsely bolster the case for higher climate sensitivity.

    There is another isuse skeptics are concerned about which your arguemnt doesn't mention or understand in the slightest. I would call it a 'manufactured' or 'superficial consensus'. Now before you stop reading, this doesnt mean conspiracy, it is simply human bias, or noble cause corruption. Some people's basic philosophical position is to bring 'order' and 'consensus' to a chaotic world, but skeptics contend this can be a dangerous or two-sided basic philosophical foundation, because inconsistency and disorder (chaos) is a fundamental principle of both nature and society, which means it is very easy for a 'manufactured consensus' to ignore the scientific reality (change/disoder/chaos).

    Skeptics contend that 'manufactured consensus' goes on all the time, and is very dfficult to eliminate, as in "The Hithchikers Guide to the Galaxy" when two war lords are at the table and one of them mutters something which turns out to be offensive to the other's mother without realising it, and all out war in unleashed. It happens (almost) without intent.

    Skeptics contend that claiming a 'consensus of evidence' with current climate data is a form of noble cause distortion/corruption. Whenever something crops up which doensn't fit the model, some research is carried out which inevitably comes up with an angle which 'makes' it fit, but in many cases such a 'fit' is entirely ambiguous. The bandwagon followers then proclaim, 'it turns out that is supports strong AGW etc etc', when the data makes no such conclusion. Skeptics contend this happens frequently. Therefore, there is no 'consenus of evidence', and overall climate sensitivity is still rightly debated.

    People in other fields such as anthrolopolgy and physics understand this process a bit better it seems. No one claims that 'dark matter' for example is a given because the data is still ambiguous. Anthrolopoloigsts consistenly find bones of hominids exactly fitting the model they were trying to prove, until somone finds another set of bones which leads to a different interpretation. They accept this sort of human bias, but they dont want to change the economy because of it.

    Becuase of this frequent distortion of 'consensus', skeptics are always trying to pick holes and weaknesses in the arguments, which is entirely reasonable given the process of human bias above. But your argument suggests all such is misguided. We should trust the funding and peer review process, the scientists. I think the diasgreements come from a different perspective of basic human nature, and a learned lack of faith in the current peer review process.

    I'll give some concrete examples, off the top of my head. There is no evidence that volcanism was stronger in the Cretaceous and that is why the c02 levels were higher and T was warmer. It is a superficial consensus focred to fit into the 'model'. Possibilities ignored include continental configuration and changes to ocean currents.

    There is no evidence that oceans acidified dramatically fast during mass extinction events and coral reefs collapsed in short periods of time, the process appears to be very slow, meaning we don't know how ocean chemistry responds to very short term c02 rises. Evidence ignored includes the oceans not diverging more than 0.6pH in the last 300 million years, which implies they are strongly buffered to c02 changes (eg dissolution/precipitaiton of carbonate sediments in the subsurface, which is larger in area than all the worlds coastal shelfs). To say that coral reefs will 'become eroding structures in 30 years' by ignoring this sort of doubt is simply following a constantly manufactured consensus. I am not using these examples as particually good examples of underlying doubts, just examples of where ambiguous data is made/manufactured to fit into a general model. It goes on all the time.

    We dont know cloud cover during the Little Ice Age or the MWP and how this affected T. We dont know overall climate sensitvity. Many other examples could be given. Skeptics will continue to focus on small pieces, big pieces, the big picture and the small picture, for as long as there is human bias, and until we have very strong confidence in overall climate sensivity, which even the politically charged, 'we exagerate for political reasons' IPCC, is unsure about.
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  17. We've got multiple, independent sources of temperature data, both surface and satellite based, that are in pretty good agreement. Objectively, the trend is significant warming. So can we at least agree that global warming is real?
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  18. Skeptics do mislead. That's a real oxymoron - a very kind labelling of somebody who cheats but expects people like us and the scientists to play by the rules.

    Derek, FoGT
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  19. MattJ #1
    You are doing the scientists a disservice - it is not like they are the ones that located those weather stations. There were other entities doing that and many of those station were established before global climate became a central issue.

    Another red herring!
    ~ ~ ~~ ~ ~ ~

    The scientist worked with the data available to them -
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  20. thingadonta, it doesn't seem like you understand how science works. Bias gets filtered out. Results are independently replicated and verified&mdash if they're not, they get tossed out. Good scientists are highly skeptical and put ideas "through the wringer" before *cautiously* starting to accept them as possible, provisional descriptions of reality. Nothing is ever "settled" in science, if new data comes along, or a better explanation that fits the data, the old ideas get tossed out the window.

    What you've described is nothing like science. Science is not about "consensus building". That sounds like politics, or simply personal opinion.

    The IPCC is decidedly conservative. Their conclusions are toned down, not exaggerated.
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  21. penguindreams I really like how you explained that so I'm going to repeat it (the rest of your post also made sense.)
    ~ ~ ~ ~ ~ ~ ~
    at 09:50 AM on 13 June, 2010
    I like E. O. Wilson's term consilience. Evidence converges towards one conclusion from a wide variety of directions. Any given line (every line) has some possibilities for error. But those possibilities and routes of error are different between the different lines. There is consilience between lines of evidence as wildly different as sea level, global thermometer networks, and the times of flowers blooming in the spring. (And many, many, more.) They all have sources of error, but each source of error could as easily point to cooling as warming. Yet there is consilience that the earth is warming.
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  22. BP, that blog post from Spencer seems to be only a blog post. Is it published? If not, why not? Considering it is not open for comments, it is conveniently shielding itself from even "blog review." If that's all there is to it, I am unimpressed.

    What does real science say about UHI and how it's dealt with in the data? Doesn't SkS have a post on that, linking real science papers? Why would it deserve less credence than Spencer's?

    How much scrutiny have you applied (as a genuine skeptic would) to this blog post? As much as you do to so-called "pro-AGW" peer-reviewed science articles? You cite it but do not provide any kind of critical analysis, where is your skepticism? What exactly is the "warm bias" on the graph and how is it calculated? How does this explain the SST increase?

    Thingadonta has a very wordy post that equally fails to impress me. Skeptics are concerned with exaggeration eh?

    What does one find on skeptic blogs?
    Stuff like this:
    http://wattsupwiththat.com/2010/05/25/the-western-snowpack-is-137-of-normal/

    Averaging percentages, without giving it much thought. Talk about exaggeration. How convenient. What would happen if so-called "pro-AGW" serious sites like RC did the same kind of abysmally stupid maths? Oh, the uproar. But, of course, that's never going to happen because the standards are different on RC. And this is just one in a long history icluding carbonic snow, and what not. What a joke.

    But there is more. What do we find in that thread? uncritical rants. How many "skeptics" apply their skepticism to the o.p.? I counted 2 before deciding that, since I have only one life to live, filling even a tiny amount of my time with the kind of stupidity found there could be a mortal sin. It's not like I don't have better things to do.

    They just go on ranting about how much snow they had this winter. Where is the subtantive discussion on data? Why is none of the regulars there addressing the stupid maths? Why is nobody saying tha the 137% figure is misleading? On the 2008 science blog of the year?

    That's what GW skepticism is, mostly (I should say overwhelmingly). I'm as unimpressed as ever. The worst part of it, and the one that applies even to the better quality skeptic contributors here, is the double standard. One-sided skepticism is no skepticism at all. Especially when it has mouthfuls of "bias" to spray on everybody.

    I'll just keep looking at what real scientists, doing real work, publish. I can't understand a lot of it, and it certainly isn't perfect. Yet it is still a better use of my time than "skeptic" internet stuff like the Spencer's post you linked.
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  23. Regarding the "global warming is caused by air conditioning" meme mentioned above...

    ...It should be noted that many air conditioners function as heat pumps during the winter. So it would seem to me that thermometers located near air-conditioning/heat-pump exhaust outlets should demonstrate, on average, a "cold bias" during the winter months.

    Has anyone involved with the surfacestations project considered this?
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  24. (From 12 above)

    #11 David Horton at 11:26 AM on 13 June, 2010
    how do I explain that to the glaciers?

    No need to explain them, they are not sentient. Just filter out soot from smoke.


    And the satellites. What about the satellite MSU data? Soot problems there, too?
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  25. It is not the amount of data that makes a theory true.

    For centuries people believed that the Earth was flat based on a multitude of "evidence".

    Data on its own does not lead to the truth and can be very misleading indeed if applied to a false hypothesis. And as long as alternative theories are not openly discussed, we are all that much poorer.

    Furthermore, the comment about false readings taken from weather stations due to air conditioners, carparks and parking lots is a strawman if there ever was one.
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  26. Some recent posts, this one included, seem to be aiming for the low end of the food chain (WUWT). So you are fighting deniers - simple, easily refuted arguments. But there are skeptic sites - like The Air Vent and The Blackboard for example - that present arguments that are both more sophisticated and more honest.

    Recent topics there that have left me wondering are:
    1) Given little change to the entire antarctic ice sheet - how much of the arctic ice sheet is due to wind and currents - ie seasonal variation.

    2) They point to the warming trend from the 1900-1930s (not sure of the dates here) - but it is a trend that lasted as long as the current, and has a similar slope.

    3) Negative response from cloud cover

    4) They invoke trends longer than we have had decent instrumentation that account for some of the warming.

    These folks acknowledge that first order CO2 forcing. They question the extent of negative feedbacks. While the balance of evidence and logic seem to support AGW - I sometimes think people are "cherry picking" the easy/dumbest things the true deniers say, and lumping all questions about the logic and science in with the low quality points - leaving some valid counter-arguments unexamined.
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  27. #15 ProfMandia at 13:17 PM on 13 June, 2010
    How much has the population grown over the oceans?

    Dear prof,

    I was talking about UHI, which obviously occurs only in land records. Oceans is another issue which should be discussed separately. I am sure you would not be happy either if at an exam a student in reply to a specific question would start talking about something else.

    The only legitimate way for you to refute Dr. Spencer's finding (which I have moved a step further by quantifying the effect) is to point out specific errors in the specific study.



    Simple handwaving or changing of topic would not do.

    Of course it is only a first approximation, so the actual numbers may be slightly different. Proper correction may be variable over time and space as well, since population growth was uneven. Also, the huge decrease in number of GHCN stations after 1990, especially urban ones is not taken into account here.

    There is certainly room for improvement but it would be nice to see the guys who are responsible for it doing their job instead of someone with no time and resources.
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  28. If UHI is as strong as you claim, BP, then why are ground station measurements (+0.17 degrees per decade since 1979) so close to those calculated by satellite measurements (+0.14 to +0.16 degrees per decade since 1979). The reality is that the entire premise of Spencer's argument is totally false-which is that adjustments aren't frequently made to account for UHI effect. Indeed, Spencer himself has a habit of failing to adjust his own satellite data to account for diurnal drift, so maybe he wrongly assumes that those on the ground are making the same basic error (which is why his readings are +0.02 degrees per decade cooler than those provided by RSS). Of course, even *if* the adjustments were not being made, several studies have shown that the difference between so-called "good" & "bad" stations is absolutely negligible.
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  29. @ actually thoughtful. Is that the best that these guys can come up with? Well I can easily debunk 3 out of 4 of these arguments without even breaking a sweat:

    1) Antarctic Ice Sheet: though it's true that total ice sheet *thickness* has increased slightly since the 1970's, ice sheet *mass* (as measured by the GRACE satellites) has actually been *shrinking*. All of the increased thickness has been *inland* & restricted to the Eastern half of the continent. This increase in inland thickness-at high altitude-is consistent with warming-induced changes to precipitation in the Southern Ocean, the same precipitation which has caused a significant increase in calving of the sea-ice.

    2) Warming from 1900-1939 vs 1970-2009: From 1900-1939, the planet warmed at a rate of +0.08 degrees per decade, which isn't surprising given that sunspot numbers increased at an average rate of 9.9 per decade over that same period. From 1970-2009, the warming rate was +0.16 degrees per decade, at a time when sunspot numbers *fell* at an average rate of 9 per decade-so its an "apples & oranges" comparison!

    3) Negative effect from clouds: as has been pointed out numerous times before, clouds act as both a negative & positive forcing. Yes they increase the Earth's albedo, but they also act to trap more IR radiation as it heads out to space. Lindzen suggested that an increase in the Iris Effect would provide a negative feedback for CO2 induced warming-by reducing the clouds that help trap IR radiation in the lower atmosphere. However, the CERES satellites showed that the Iris effect lets more radiation *IN* than it lets *OUT*, thus providing a modest *positive* forcing.

    I'd debunk argument number 4 too, except I don't understand what you mean by the question!
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  30. Berényi Péter,
    could you please explain how did you build the graph you show?
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  31. The problem I have is that even when you present extensive lists of data such as

    •Ice sheets are melting
    •Sea levels are rising
    •Biological changes in tens of thousands of species
    •Glaciers are retreating
    •Seasons are shifting
    •Species are becoming extinct

    is that AGW isn't the only explanation for each of these observations. You describe sceptics as being myopic but I'd say your own explanation suffers from tunnel vision by ignoring natural variations in the climatic and biological systems.
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    Response: "The problem I have is that even when you present extensive lists of data ... is that AGW isn't the only explanation for each of these observations"

    Agreed, evidence of global warming doesn't necessarily prove human caused global warming. Which was why I preceded it with the various lines of evidence for a human fingerprint in climate change: It's not just one piece of evidence that convinces me that humans are causing global warming but that independent sets of measurements of completely different parts of the climate all find a human fingerprint, exactly as we expect.
  32. actually thoughtfull,
    you're actually right that WUWT is not even to be considered when talking about the science of global warming. Unfortunately it's the most quoted source of skeptc arguments and way too often even skeptic scientists use it for their claims that would not pass peer review. Like it or not, we have to live with it.
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  33. HumanityRules,
    unfortunately no one still came out with comprehensive alternative explanations. As John says in this post, the "strategy" is to pick them up one by one.
    And please notice, skeptics love to endlessly repeate the mantra that the "AGW camp" does not consider natural variations. It's simply untrue, it's just the hope that repeating something enough times will make it true.
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  34. The skeptics on this blog constantly suffer from the can't see the forest for the trees syndrome. HR #31 sums it up "AGW isn't the only explanation for each of these observations", well, possibly, but I suggest you would have a hard time coming up with alternatives for them. Whanna try? But that isn't the point, even if you could come up with a series of disparate (and my guess would be, often contradictory) explanations. These things are happening at an incredibly fast rate. They are happening at this incredibly fast rate at a time when CO2 levels are rapidly increasing. We know the causal relationship between those two things. Every observation of the natural and geographic worlds fits consistently with this single theory.

    A Darwin said, about evolution, find just one piece of evidence against it and the whole theory collapses. Same here. Want to give that a try Mr Rules?
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  35. #28 Marcus at 19:25 PM on 13 June, 2010
    If UHI is as strong as you claim, BP, then why are ground station measurements (+0.17 degrees per decade since 1979) so close to those calculated by satellite measurements (+0.14 to +0.16 degrees per decade since 1979).

    You are doing the same thing most everyone seems to do here. Talking about something else.

    several studies have shown that the difference between so-called "good" & "bad" stations is absolutely negligible

    You are echoing the claim promoted by RealClimate.

    "the UHI effect makes at most a contribution of 0.05°C to the warming observed over the past century"

    It is equivalent to saying if local population density in an area is doubled, temperature readings would increase by 0.027 K (while the actual value is close to 0.16 K). To refute this, no detailed scientific study is needed, just a bit of common sense. If it were true, the phenomenon called UHI (Urban Heat Island) would never even be noticed.

    BTW, the difference between "good" & "bad" stations in itself does not have much to do with UHI effect on temperature trend. The difference between logarithmic local population density trends have, and studies referenced by RealClimate only show this trend must have been a bit higher for stations flagged "rural" in GHCN than for stations flagged "urban". If anything, this implies GISTEMP practice of adjusting urban trends to surrounding rural readings introduces some more warming bias, not less.

    #30 Riccardo at 19:41 PM on 13 June, 2010
    could you please explain how did you build the graph you show?

    I could. However, please read #10 & #27 first carefully, follow the links provided, try to understand what is said. Having done that you'll most probably understand the graph.

    If not, you can still ask specific questions. The answer would be detailed enough to be scrutinized thoroughly. That's the only way to proceed.
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  36. I'm not "talking about something else" BP-my question relates directly to the clearly false claim that UHI effect can explain the warming of the past century. After all, if it was a strictly linear effect induced by increasing population density-then why is warming occurring fastest in parts of the world which show the *slowest* rates of increase in population density (i.e. in the rural parts of the world)? Why does temperature first peak in the 1940's, then fall away around the 1950's (if it was simply down to population density induced UHI, then the warming should continue unabated)? How come Dr Spencer is apparently the *only* man who can see, & correct for, the UHI-even though dozens of other researchers apparently can't-when he is apparently unable to see, & correct for, the diurnal drift in his own satellite temperature measurements? If UHI is such a big effect, as you & Spencer claim, then it should show up in a comparison between ground-based & satellite-based temperature measurements, yet they're almost identical (even when you allow for Spencer's failure to account for diurnal drift). So your attack on my post is really just a desperate attempt to distract people from the fact that you can't answer a number of *very* obvious questions (including the one by ProfMandia about warming over the oceans-which is also relevant in terms of debunking the whole UHI argument).
    Still, at least your post serves as a fantastic object lesson about how the skeptics seek to deceive & distract people.
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  37. HumanityRules. The problem is that, for most of the things John mentions, natural variation suggests we should be moving in the *opposite* direction. After all, after CO2, the primary driver of our climate is solar activity. Over the last 30 years, solar activity has been trending *downwards*, yet global temperatures are rising faster than at any other point in the past 150 years of temperature records-even when solar activity was rising quite rapidly. So, in the absence of rising solar activity, how else can *you* explain all of these events that John describes?
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  38. Another point, BP. Between 1900 & 1964, the global population more than *doubled* (1.6 billion people to 3.3 billion people), yet the rate of warming measured over that time period by ground-based stations was about 0.06 degrees per decade. Between 1965 & 2006, the global population *almost* doubled (3.3 billion to 6.5 billion people), yet the rate of warming measured by ground-based stations was +0.154 degrees per decade). So if warming was entirely down to population-density induced UHI, then we would have expected a greater rate in measured warming in the first 65 years of the 20th century (especially when you *also* consider rising sunspot activity & lack of volcanic activity). Seems that neither Dr Spencer-nor yourself-have actually thought this through very well!
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  39. Couldn't "The case for human caused global warming is based on many independent lines of evidence." just be seen as an example of a robust confirmation bias? Are there no sources that throw doubt on any of the individual conclusions of the "independent lines of evidence"? Are there no lines of evidence showing global cooling or a less drastic global warming or a non-human caused Global warming?

    Can there be no legitimate skepticism of AGW? To my mind only ideological epistomologies would be immune from skepticism but that would make AGW antithetical to science.

    lff
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  40. Iff, genuine scientific skepticism is to *not* accept any claim until you've seen evidence to back it up, & a willingness to accept contrary evidence should it come to light. Yet to this date, the majority of so-called "skeptics" have failed to produce any contrary evidence to debunk anthropogenic global warming-instead choosing to come up with half-baked hypotheses that don't stand up to scrutiny by any half-way impartial reviewer. They spend the rest of their time launching crude ad-hominem attacks on climate scientists & trying to influence the mainstream media with anti-AGW PR campaigns. All of which I'd call entirely *antithetical* to science!
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  41. #36 Marcus at 21:30 PM on 13 June, 2010
    if it was a strictly linear effect induced by increasing population density-then why is warming occurring fastest in parts of the world which show the *slowest* rates of increase in population density (i.e. in the rural parts of the world)?

    You are not listening. UHI is not a linear function of population density, it is a linear function of the logarithm of it. Big difference.

    You can have a slow increase in absolute numbers at sparsely populated areas while a huge UHI effect at the same time.
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  42. Also Iff, its not like the theory of AGW just appeared & gained acceptance overnight. No, it required an enormous amount of work-over multiple generations-to discover & bring together the various lines of evidence which explained how & why the planet was warming at the rate it currently is-& how & why humans are responsible.
    When the so-called skeptics are prepared to invest the same time & energy into developing an alternative theory to explain recent warming trends-instead of clinging to skepticism on strictly ideological grounds-then they might regain some measure of credibility.
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  43. What, even parts of the world where population densities haven't increased *at all*? Like the Antarctic & Arctic BP? It seems like *you're* the one who isn't listening around here. We're not simply talking rural as in "Backwoods USA", we're talking about "rural" as in the middle of nowhere-temperature records in parts of the world which have experienced virtually *no* increase in population density at all. It also doesn't explain why temperatures briefly peaked in the 1940's, then fell away again, before rising again from the 1950's onwards. You see, as much as you try and obfuscate, BP, the reality remains that you don't have explanation for all the errors in Spencer's UHI hypothesis. Even if he was correct, though, & we were forced to discard *all* the warming measured by ground-based measuring stations, we're still left with a +0.16 degree per decade warming from 1979-2009-as measured by satellite-that no amount of hand waving can cause to vanish!
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  44. RSVP @ 25 said:

    "It is not the amount of data that makes a theory true.

    For centuries people believed that the Earth was flat based on a multitude of "evidence"."

    So what constituted the "multitude of evidence" that the Earth was flat? It was known by the ancient Greeks that the Earth was spherical, Erathosthenes even came up with an impressively (for the time) accurate estimate of the Earth's diameter. I don't think anyone has ever thought of the Earth as flat based on evidence.

    However, you are right that no amount of evidence can show a theory is true, as explained in Popper's ideas about falsifiability. Evidence can only falsify theories, not prove them. The evidence falsifies many skeptic theories, for instance the fact that the increase in atmospheric CO2 being smaller than anthropogenic emissions is inconsistent with the oceans being the cause of increasing atmospheric CO2.

    The point is that multiple lines of evidence provide good corroboration for AGW, while not proving it. That is the best science can do, provide the best explanation for the observed facts and weed out the theories that don't fit the facts.
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  45. #39 Marcus at 21:46 PM on 13 June, 2010
    if warming was entirely down to population-density induced UHI, then

    It's getting tiresome. Go back please and check what I have claimed.

    I said UHI is responsible for about 0.29 K/cy of the 0.65 K/cy warming shown by GISTEMP (possibly a little bit more for other reasons, e.g. specific GHCN station dropout patterns and adjustment to rural surrounding). Where do you find your "entirely" here?
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  46. Beranyi provides another great object lesson about the tactics of the so-called skeptics: if you're losing the argument, change the goal-posts. Until recently, the hue & cry of the skeptic movement was "the ground-based stations can't be trusted because too many of them are in urban locations-subject to the UHI effect". Now that this myth has been debunked, apparently the hue & cry has become "the ground-based stations can't be trusted because too many of them are in *rural* locations". Can't they at least be *consistent*? I do really love, though, how Beranyi is convinced that Spencer is some kind of uber-genius how can see the "obvious flaw" in the ground-based data that somehow hundreds of other researchers just happened to miss (oops, thats right-they didn't miss it, its all part of some global conspiracy-sarcasm btw). We're talking about a guy here who didn't have the wherewithal to account for something as obvious as diurnal drift in satellite temperature measurements-so how can we take him seriously? Also, Beranyi, are your calculations akin to your "back-of-the-envelope" calculations regarding argon?
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  47. #47 Marcus at 22:28 PM on 13 June, 2010
    Can't they at least be *consistent*?

    As far as I can see I am the only one here trying to keep up some reasonable level of consistency. Of course we could discuss other issues like SST or satellite data or the strong negative correlation between number of pirates and global average temperature, but its more expedient to stick to a single problem at a time and analyze that piece dispassionately.

    are your calculations akin to your "back-of-the-envelope" calculations regarding argon?

    Not likely. But you are here to check them. Much better pastime than submerging in rhetoric.
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  48. Berényi Péter,
    i did read, in fact. Still you did not say what you did to make the graph. If I have to judge from your previous comments, I'd say that you just scaled the GISS meteo-station dataset. This would be so blatantly wrong that I'm sure you did not do it. This is why I ask.
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  49. #49 Riccardo at 23:21 PM on 13 June, 2010
    you just scaled the GISS meteo-station dataset

    Of course I did. I have subtracted the spurious trend due to UHI. What's wrong with that? Explain.
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  50. Sometimes these skeptic arguments are just plain funny and fall flat of their own weight; sometimes it takes a little digging to see the flaws.

    #25 "false readings taken from weather stations due to air conditioners, carparks and parking lots is a strawman if there ever was one."

    A strawman indeed! The USEIA provides a massive amount of statistics on energy source, use, etc. One such data table yields a graph of the burgeoning use of AC by US census region:



    Note that the south consistently accounts for nearly 50% of the total number of US households with AC. Note, too, that the slope of the southern region graph is the steepest (although by the 1997 entry, only 7% of southern US households had no AC of any kind, so that should level off).

    It's obvious that the southern US is warmer than the northern US (trust me on that one, I have the electric bills to prove it!), but how do the long term trends in temperature compare? If AC is such a significant factor in distorting the record, surely the rapid rise of AC in the south results in a much steeper temperature profile (graph of temperature vs. year) than the north?

    Temperature records for most US states are searchable with a snazzy map-based interface here; many are continuous back to 1895. So here is a composite of temperature index (in deg C, relative to period averages) for northern states vs. southern states:


    Alas for the strawmen, the regional trends since the 1980s are very similar. All those southern AC units are not making a difference in the temperature indices (except, as UP #13 eloquently pointed out, by 'sucking up untold megawatts' of coal-generated electric power).

    Interesting tidbit: According to USEIA Table 1, here, since 1990 the use of energy (measured in Quad BTUs) for AC in the US has decreased due to increasingly higher efficiency. Yet the trend of the temperature indices is inexorable.
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