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What I learned from debating science with trolls

Posted on 29 August 2014 by Guest Author

By Michael J. I. Brown, Monash University

I often like to discuss science online and I’m also rather partial to topics that promote lively discussion, such as climate change, crime statistics and (perhaps surprisingly) the big bang. This inevitably brings out the trolls.

“Don’t feed the trolls” is sound advice, but I’ve ignored it on occasion – including on The Conversation and Twitter – and I’ve been rewarded. Not that I’ve changed the minds of any trolls, nor have I expected to.

But I have received an education in the tactics many trolls use. These tactics are common not just to trolls but to bloggers, journalists and politicians who attack science, from climate to cancer research.

Some techniques are comically simple. Emotionally charged, yet evidence-free, accusations of scams, fraud and cover-ups are common. While they mostly lack credibility, such accusations may be effective at polarising debate and reducing understanding.

And I wish I had a dollar each time a scientifically incompetent ideologue claimed science is a religion. The chairman of the Prime Minister’s Business Advisory Council, Maurice Newman, trotted out that old chestnut in The Australian last week. Australia’s Chief Scientist, Ian Chubb, was less than impressed by Newman’s use of that tactic.

Unfortunately there are too many tactics to discuss in just one article (sorry Gish Gallop and Strawman), so I will focus on just a few that I’ve encountered online and in the media recently.


Internet trolls know who their experts are. There are thousands of professors scattered across academia, so it isn’t surprising that a few contrarians can be found. In online discussions I’ve been told of the contrarian views of “respected” professors from Harvard, MIT and Princeton.

Professors with contrarian views can even be found at Ivy League universities such as Princeton. Flickr/Sindy Lee, CC BY-NC-ND

Back in The Conversation’s early days I even copped abuse for not being at Princeton by someone who was clearly unfamiliar with both science and my employment history. It was a useful lesson that vitriol is often disconnected from knowledge and expertise.

At times expert opinion is totally misrepresented, often with remarkable confidence.

Responding to one of my Conversation articles, the Australian Financial Review’s Mark Lawson distorted the findings of CSIRO’s John Church on sea levels.

Even after I confirmed with Church that Lawson had the science wrong, Lawson wouldn’t back down.

Such distortions aren’t limited to online debates. In The Australian, Maurice Newman warned about imminent global cooling and cited Professor Mike Lockwood’s research as evidence.

But Lockwood himself stated last year that solar variability this century may reduce warming by:

between 0.06 and 0.1 degrees Celsius, a very small fraction of the warming we’re due to experience as a result of human activity.

Newman’s claims were debunked, by his expert, before he even wrote his article.

Sometimes experts are quoted correctly, but they happen to disagree with the vast majority of their equally qualified (or more qualified) colleagues. How do the scientifically illiterate select this minority of experts?

I’ve asked trolls this question a few times and, funnily enough, they cannot provide good answers. To be blunt, they are choosing experts based on agreeable conclusions rather than scientific rigour, and this problem extends well beyond online debates.

Earlier this month, Senator Eric Abetz controversially seemed to link abortions with breast cancer on Channel Ten’s The Project.

While Abetz distanced himself from these claims, his media statement doesn’t dispute them and talks up the expertise of Dr Angela Lanfranchi, who does link abortions with breast cancer.

Abetz does not have expertise in medical research, so why did he give Dr Lanfranchi’s views similar or more weight than those of most doctors, including the Australian Medical Association’s president Brian Owler, who say there is no clear link between abortion and breast cancer?

If Abetz cannot evaluate the medical research data and methods, is his choice largely based on Dr Lanfranchi’s conclusions? Why won’t he accept the views of most medical professionals, who can evaluate the relevant evidence?

Abetz may be doctor shopping, not for a desired diagnosis or drug, but for an desired expert opinion. And just as doctor shopping can result in the wrong diagnosis, doctor shopping for opinions gives you misleading conclusions.

Broken logic

Often attacks on science employ logic so flawed that it would be laughable in everyday life. If I said my car was blue, and thus no cars are red, you would be unimpressed. And yet when non-experts discuss science, such flawed logic is often employed.

Carbon dioxide emissions are leading to rapid climate change now, and gradual natural climate change has also taken place over aeons. There’s no reason for natural and anthropogenic climate change to be mutually exclusive, and yet climate change deniers frequently use natural climate change in an attempt to disprove anthropogenic global warming.

Global temperatures (measured by Marcott et al. in dark blue, and HadCRUT4 in red) have changed as a result of both natural and anthropogenic climate change. There has been a dramatic rise in global temperatures over the past century. Michael Brown

Unfortunately our Prime Minister, Tony Abbott, employed similar broken logic after the 2013 bushfires:

Australia has had fires and floods since the beginning of time. We’ve had much bigger floods and fires than the ones we’ve recently experienced. You can hardly say they were the result of anthropic [sic] global warming.

Bushfires are a natural part of the Australian environment but that does not exclude climate change altering the frequency and intensity of those fires. Indeed, the Forest Fire Danger Index has been increasing across Australia since the 1970s.

Why the Prime Minister would employ such flawed logic, and contradict scientific research, is puzzling.


The Italian scientist and astronomer Galileo Galilei was infamously persecuted by the politically powerful Catholic Church because of his promotion of the sun-centred solar system.

Galileo Galilei understood the power of observations. Wikimedia

While Galileo suffered house arrest, his views ultimately triumphed because they were supported by observation, while the Church’s stance relied on theology.

The Galileo Gambit is a debating technique that perverts this history to defend nonsense. Criticisms by the vast majority of scientists are equated with the opinions of 17th century clergy, while a minority promoting pseudoscience are equated with Galileo.

Ironically, the Galileo Gambit is often employed by those who have no scientific expertise and strong ideological reasons for attacking science. And its use isn’t restricted to online debates.

Bizarrely, even the politically powerful and well connected are partial to the Galileo Gambit. Maurice Newman (once again) rejects the consensus view of climate scientists and, when questioned on his rejection of the science, his (perhaps predictable) response was:

Well, Galileo was virtually on his own.

Newman’s use of a tactic of trolls and cranks is worthy of criticism. The triumph of Galileo’s views were a result of his capacity to develop scientific ideas and test them via observation. Newman, and many of those who attack science, notably lack this ability.The Conversation

Michael J. I. Brown receives research funding from the Australian Research Council and Monash University.

This article was originally published on The Conversation. Read the original article.

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Comments 1 to 50 out of 76:

  1. Some techniques are comically simple. Emotionally charged, yet evidence-free, accusations of scams, fraud and cover-ups are common. While they mostly lack credibility, such accusations may be effective at polarising debate and reducing understanding.

    Those appear to be the perennial favourites of the "regulars" who blight the comment threads of Dana & John's posts at The Guardian.

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  2. Godwin's Law - As an online argument grows longer and more heated, it becomes increasingly likely that someone will bring up Adolf Hitler or the Nazis. When this event occurs the person guilty of invoking Godwin's Law has effectively forfeited the argument.

    The Al Gore Corollary to Godwin's Law - As an online argument on Climate Change grows longer and more heated, it becomes increasingly likely that someone will bring up Al Gore. When this event occurs the person guilty of invoking Al Gore's name has effectively forfeited the argument and lost the debate, badly.

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  3. Nice article and comments. In my experience, Scott D. Weitzenhoffer's comment on arguing with Creationists applies equally well to most denialists: 

    "Debating creationists on the topic of evolution is rather like trying to play chess with a pigeon — it knocks the pieces over, craps on the board, and flies back to its flock to claim victory."

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  4. There's even a "Galileo Movement" in Australia set up to fight against carbon taxes. They were the folks who foot the bill for Monckton's tour.

    I'll not link to them for obvious reasons.

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  5. The Galileo Gambit is wrong at a deeper level. NO one denied that the planets moved "funny". With deniers, they are denying the phenomenon itself, not the explanation for it.

    A better analogy would be with plate tectonics which is also mentioned by deniers. Those against plate tectonics denied (nonvertical) movement itself, not the explanation for movement.

    But of course they would come off looking rather worse in that analogy.

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  6. One tactic I could have mentioned is "We can all agree... " or "It is uncontroversial... " followed by a statement that most scientists would either disagree with or class as a debatable.

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  7. longjohn119 @ 2,

    I would like to claim an exception to the Al Gore Corrollery to Godwin's Law.

    I will occasionally bring up Al Gore's book "The Assault on Reason" as recommended reading. Like I just did here.

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  8. Nick Cater of The Australian and Centre for Independent Studies (an Australian libertarian think tank) used an interesting variation of the Galileo Gambit when attacking the Press Council.

    Rather than emphasise the comparison of Andrew Bolt to Galileo (which would very absurd), Cater compared the Press Council to Galileo’s accusers (still absurd).

    Press Council adjudications seem considerably milder than accusations of heresy and the inquisition. For a start, the Press Council didn't force Andrew Bolt to recant his views. Also, issues of statistical significance and not misrepresenting the UK MET office seems more grounded in reality than a 17th century theological argument against a heliocentric cosmology.

    Some key parts of the Press Council adjudication follow:

    “The Press Council has concluded that Mr Bolt was clearly entitled to express his own opinion about the Met Office data but in doing so he needed to avoid conveying a misleading interpretation of the Met Office’s own views on its data”.

    Given the great public importance of these issues, Mr Bolt should have acknowledged explicitly that all of the three changes in question were comparatively short-term and were statistically compatible with continuance of the long-term trends in the opposite direction. On the other hand, the article referred to the possibility that global warming has merely “paused” and it emphasised the need to “keep an open mind” on these issues. Accordingly, despite concerns about the manner in which the available evidence is presented, the Council’s decision is not to uphold these aspects of the complaint.

    The Council emphasises that this adjudication neither endorses nor rejects any particular theories or predictions about global warming and related issues. It observes that on issues of such major importance the community is best served by frank disclosure and discussion rather than, for example, failure to acknowledge significant shorter- or longer-term trends in relevant data."

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  9. The power of carefully developed and targeted misleading marketing is undeniably a tool the climate change deniers revel in abusing.

    And I would not use the term 'trolling' to refer to attempts to keep other people from better understanding a subject like climate science. Those efforts are not just attempts to trigger an emotional response from the target, the more commonly understood objective of a troll.

    Those who attempt to discedit the developing better understanding of climate science attempt to appeal to people who have a strong tendency to be srongly motivated to believe a made-up claim that suits their interest. That is not the same as trolling, it is far more damaging.

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  10. I agree that not all the tactics I discuss are trolling, but they are definitely tactics commonly used by trolls I have encountered (and used by others who aren't trolls).

    Flawed logic isn't trolling, but claims of fraud (without evidence) and equating sciences with religion can be (depending on the intent). 

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  11. There's a serious problem of psychological projection in the way 'skeptics' discuss climate science. Things like "vested interests of alrmists" or "CAGW is driven by emotion, whereas skeptics are driven by science" make me think this is a vast unexplored ground for psychological research.

    One day it will be dismissed as an absurd that today people point to research grants as an economic power big enough to overthrow the multi-trillion dollar fossil fuel industry.

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  12. The best tactic I've found for tackling climate change deniers in a public forums is to ask them this question: 

    "If the planet were really warming then what evidence would be enough to convince you to change your mind?"

    The subsequent exchange usually makes it clear to everyone that absolutely nothing, either real or theoretical, would be enough to convince them to change their viewpoint. 

    This is very similar to debating with creationists.  As someone said:

    For a creationist to accept evolution, no evidence is good enough.
    For a creationist to believe in a god, no evidence is good enough.

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  13. And then there's the "So you are saying ..." formulation, which is followed by something that's not even close to what you actually said:

    "Increased CO2 inevitably leads to warmer temps."
    "So you are saying that CO2 is the only cause of climate change?"

    I love that one.

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  14. @Alexandre #11: There's another area that's begging for psychological examination: The "skeptics" never, ever, understand analogies. They fixate on what's different, ignore what's the same, and announce that the analogy is "moronic."

    In my experience, the failure rate on "skeptic" comprehension of analogies is close to 100%.

    I'd love to know why this is. Do they actually not get the analogies, or are they just scratching for some way around them?

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  15. @chrisd3 #14:  I'm not really sure what you mean about "skeptics understanding analogies". Could you give a couple of examples?



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  16. Chris/Jenna - Surely "analogies" are ripe for "misunderstanding", deliberate or otherwise?

    I actually have an entire website devoted (almost) entirely to debating Arctic sea ice science with "skeptics". You might find the current "debate" instructive:

    What "analogy" do you suggest I use in my thus far vain attempts to get the real scientific message across?

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  17. @jenna...

    Already done above. The Galileo [ and I could add Copernicus/Einstein/ulcer...] Gambit is a clear example in that deniers deny the basic phenomenon that the Earth is warming "just like" the above thinkers provided much better explanations for phenomena everyone in the world already agreed occurred in the first place. No. It is not at all "just like". They are false analogies.

    The correct analogy would be that deniers are like flat Eathers, young Earthers, and, for a good real science analogy, the uniformitarian resistance to the concept of the horizontal movements of continents.

    Another correct analogy would be that deniers act like parts of the economic/political entities affected by lead, asbestos, HFC, tobacco, and acid rain emitters/producers. The arguments provided by the deniers in each case really are "just like". And very wrong in the very same ways for the very same reasons.

    What christd3 is pointing out is that, among other analogies, deniers are incapable of discriminating case #1 from cases #2 and #3.

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  18. @jenna #15

    OK, here's an example. A common "skeptic" argument is that temperatures rose in the past (before the use of fossil fuels); those increases must have had natural causes, which means that the current warming must also be natural.

    In an attempt to show that things can have more than one cause, I've used this: "My neighbor's car accelerated when he pushed it off a cliff. Therefore stepping on the accelerator cannot be what's causing my car to go faster now." They do not get this. They go off about how comparing climate change to driving is stupid. 

    Or there's this very common one: "Wildfires occur naturally, therefore today's fire cannot have been caused by careless campers as the fire service claims." The usual response to this is that there's no evidence that climate change causes wildfires. (Yes, I know, it's bizarre.)

    It really doesn't matter what the analogy is. Make any analogy regarding climate change. They never get it--or they pretend not to.

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  19. There are several principles that might also be relevant in debating with climate deniers and their associated trolls.

    First, you might be dealing with a possible variation of the Dunning-Kruger effect, which, in this case, would be; that if you’re ignorant, then you don't know you’re ignorant because you don't have the skills to realise that you are ignorant.

    Second, there's a quote from Alexander Canduci's book "Triumph and Tragedy" about Rome's Emperors describing the Eastern Emperor Basiliscus (ruled 475-476) which states: "It says a lot about a man's character if he can completely ignore his own manifest inadequacies". This could be applicable to some of our so called business leaders and politicians who are deniers out of ideology and self-interest.

    And third there's Euclid's "pons asinorum", his bridge of fools for students studying geometry, which in climate science relates to how greenhouse gases and warming relate to each other. Those who don't even accept this basic principle are probaly not worth debating anyway, because if you argue with a fool, people mightn't know the difference. Unfortunately, sometimes it is necessary because you might need to actually question a denier to reveal their ignorance. The trick is to do it without appearing smug and arrogant. Sadly, deniers and trolls don't make it easy, but then all you asking of them is to pay attention to the real world, listen to the people who have devoted their lives to studying it, assimilate the information and come to a proper scientific conclusion. This after all that is what real science is about anyway.

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  20. @ One Planet Only and For Ever: Exellent distiction. The term Troll and and Trolling is almost meaningless to me. I too see the "disinformation agent" as distinct from their "target to disinform," and then the "disinformed." And then there is the rare person who actually believes differently based on reason.

    I take it as a job to adress the issue against the disinformed, and the disinformeres. I think I can tell the difference by the way they respond. But it seems if we let them just say nonsense without correction, the disinformation effort wins.

    The accepted wisdom seems to be "not to feed the trolls," I disagree; it is bothersome and a never-ending battle, but a necessary fight.

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  21. @Jim Hunt #16:

    Well, arguing with Steve/Tony and his followers is utterly hopeless. It's a twisty maze of passages, all alike. No analogy is going to help.

    By the way, your first Arctic map--is that a map, or a drawing of a chicken? :)

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  22. @PluviAL #20

    The accepted wisdom seems to be "not to feed the trolls," I disagree; it is bothersome and a never-ending battle, but a necessary fight.

    I agree. "Don't feed the trolls" is good advice for real trolls--the ones who are there only to disrupt and irritate.

    But that's not the main aim of most the "skeptic" commenters (although they certainly don't mind if they disrupt and irritate). Most of them, with the exception of the professional disinformers, actually believe what they write. They are pushing a point of view. It's important not to leave this stuff unresponded to. The number of people who just read comments is much larger than the number of commenters. Bad science can look like good science to them if no one rebuts it.

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  23. @Chris #21

    At what venue might an analogy assist then?

    I negotiate the maze of twisty passages, all alike, in the perhaps naive belief that some people read that stuff who aren't dyed in the wool "skeptics". Am I in fact wasting my time?

    My first Arctic map was carefully cloned from (un)Real Science, where Steve/Tony unaccountably neglected to paper over the "Pole hole"!

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  24. @christd3

    The proper response to the "fires occur naturally" meme is to suggest they light a bonfire in their own living and then report back on how that went for them personally. This actually IS a correct analogy.

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  25. Other patterns of troll behaviour include the 'look over there' response to unwelcome evidence, and the zombie-like reemergence of refuted claims and arguments.  Together, they create a simple-minded dance whose steps always circle back to the same conclusions: telling new evidence forces trolls to change the topic, but once the new evidence has faded from the headlines, the  zombie claims it had refuted revive to walk the land again, befuddling new victims and reinforcing the convictions of people with strong commitments and short memories.

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  26. The Ostrich
    As a species I sometimes wonder if we most resemble the ostrich. If we duck our heads, ignore the problem for long enough, it will just, maybe, hopefully, please, go away. Or perhaps our approach is more like Bill Clinton's solution to gays in the military - don't ask, don't tell! After all, if nobody talks about it, it isn't there, is it?
    My brother-in-law, a house painter and his friend, who is working in the Alberta oil patch sum it up this way: "it's been about 150 years since the Industrial Revolution and we've done this much damage to the environment. We might get another 100 years out of it all."
    At a church luncheon, a fellow parishioner relates to me his experience of reading about the poisoning of the St Clare River at Sarnia. "I was there the night the company put that stuff in the ground and supposedly sealed it off." There was pain in his eyes and no doubt, in his heart and in his soul. I stated that it was amazing how many people I speak with, ordinary people, blue collar workers, who understand that we are gradually destroying the planet. He casually observed, "there will be a revolution."
    It's hardly unlikely that for some inexplicable reason, I am the only guy who has these conversations. It is more likely that most of us see the truth for what it is. We are gradually, speeding up, speeding up, speeding up, destroying the very planet that gives us life. Suicide or madness? Take your pick, I can't figure it out.
    I wonder who our political leaders talk to? Do they have these conversations or are they shielded for their own protection? They don't appear to be losing much sleep about it all as the oil companies drill away, as the auto manufacturers continue to turn out the gas combustion engine, as poisons are released into our rivers, lakes, oceans, landfills - anywhere the millions upon millions of barrels of poisonous waste can be hidden for awhile. Long enough, they hope, to finish making the money, packing up and leaving the deadly stuff behind. Perhaps, like Chernoble, the animals will have another paradise, free of humans, in a future that may be as inevitable as the prediction of my house painter friend - a hundred years or so.
    Is it possible to change a future that is rushing towards us virtually unhindered except for sporadic demonstrations and vocal minorities who are often perceived as "radical", "inhibiting progress", "tree-huggers", "terrorists", "trouble - makers", etc? Most days are like today - I simply have no idea whether we have the rational or empathetic ability to slow down, stop and possibly reverse the race to the "end of the human race."
    Joe Wiseman

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  27. As a science-friendly layman, I must admit I am pretty disillusioned by the whole commenting experience, especially on popular media sites such as Yahoo Science, which seems now to be almost exclusively occupied by trolls,  human or otherwise, spewing a wide variety of psuedo science, homespun homilies, and flawed arguments.

    Is there any reason not to be pessimistic after reading Popular Science's comments discontinuation rationalization, Brossard and Scheufele's NY Times piece, the Monbiot pieces on industry-financed and computer-generated trollery? How does one debate a computer program or even know the difference? I began commenting for the possible benefit of any impressionable casual readers who might have been getting misinformed otherwise, but if it's true that just one firmly stated ad hominem or negative implication by a denier can pretty much invalidate the whole logical component of the debate, what's the point of persisting with it - especially against such great numbers?

    In my Southern California community, the "skeptivist/denialist" propaganda strategy is clearly working. In our junior college it's practically impossible to find anyone in a trade department who doesn't believe that AGW is nothing more than a political ploy and tax-raising scheme. One automotive instructor even spends a whole lecture period each semester railing angrily against the evils of "emotional tree huggers" and "politicians," and utilizing every denialist talking point imaginable to convince his students of the "massive fraud" of global warming.

    I would like to believe I can make even a small a difference, but it's getting increasingly more difficult.

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  28. I am in the same position as Christopher Gyles (above) and am as frustrated as he with the "tactics" (my quotes) of the deniers, most of whom seem completely devoid of any knowledge of the scientific method: indeed, seem proud of the fact.

    However, TV, the press, blogs and - shamefully, this site - almost without exception avoid the BIG elephant in the room: population.

    Far too many of what might be loosely called the "green" lobby are resigned to cutting the West's consumption of energy and raw materials generally. I think we are all approaching the resource, and CO² question from exactly the wrong end: surely the way to start is to ask what is the population that the planet can sustain indefinitely, with every member of the human race having a reasonable standard of living? ( Say, for the sake of argument, that of a middle class European's lifestyle.)

    I suspect that the answer would be far short of the 9Bn plus that is forecast for 2050 - and almost certainly far short of the present 7Bn.

    In this context, CO² and consequent global warming is only one of the massive problems rapidly approaching. There is no realistic prospect of Western communities volutarily reducing their lifestyles to that of the majority of the world's people and to be honest I don't see that would do any more anyway than kick the can just a few yards down the road.

    Controlling population is the key, but if you think cutting emissions is an uphill battle it's nothing compared with fighting THAT elephant.

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  29. One of the most curious tactics used by trolls, amongst others, is the absurd strawman. For example, claims that scientists have ignored the influence of the Sun on climate. It is trivial to disprove this by looking at the discussion of "forcings" in the IPCC reports.

    Examples of this tactic can be easily found on twitter: (although this search mostly finds unrelated material).

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  30. I understand that SkS's REPOST feature is gone.

    But SkS still has the CreativeCommons and sharing/reposting policy in place... right?

    I'd love to repost this article - 

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  31. About Galileo, if anyone is curious about what the Catholic historians have to say about that specific:

    ~ ~ ~

    The logic has always amazing me since Galileo was battling a dogmatic faith-based organization.  On top of that a little closer look reveals someone who was looking for a fight and found it... more a case of ego than the sanctity of science was involve.

    But then buried in there is the implication that science and religion are somehow synonymous - a balded faced lie they don't mind boostering with all the creative cynical word-play at their disposal. 


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  32. My experience with trolls encompasses both climate change deniers and evolution deniers. Their most common tactic is to denounce any and all scientific, evidence based statements as religious justification for obtaining government grants which are themselves evidence of a gigantic conspiracy involving all the world's scientific societies as well as individual scientists. Anything you say in response will be attacked in similar terms. All this delivered with scathing invective and plenty of ad hominem rhetoric. There is simply no way to break through to them since they have already rejected the logical, evidence based way of reasoning that we take for granted. Whether they do this for personal, religious reasons or because they are in the pay of the fossil fuel interests is impossible to say and frankly, does not matter. Their object is to sway public opinion against science and scientists by relentless, unending assaults. Responding to them merely fuels the fire and may be seriously counter-productive.

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  33. Wol @28

    I disagree that cutting emissions is harder than reducing population growth. According to Hans Rosling we have already reached "peak child" or  at least "plateau child": there are more or as many children alive to day than there ever will be in the future. Population will continue to grow, perhaps to 9 billion, because today's children will inevitably become parents. The great news is that nearly every country is now appraoching low numbers of children per women. If this continues, then population should stablize around 9-10 billion.

    In contrast, emission rates continue an upward climb and nobody has a clue where the concentration of CO2 in the atmosphere will plateau and when the rate of emissions will equal the rate of absorption in the oceans and biosphere. Population almost certainly will increase by 30-40% and then likely stop growing. CO2 concentrations could more than double and there is no sign of the growth curve bending downward yet.

    I agree that it is hard, probably impossible, to imagine 10 billion people in the future living the way we do in rich countries today. But it does not follow that that the lot of the poor cannot greatly improve, while the wealthy scale back our often wasteful and extravagant ways. Technology is no panacea, but, if history is a guide, there are grounds for optimism. The Malthusians have been wrong before and let's hope that they will be wrong again.

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  34. There are a surprising number of claims that the heliocentric model was not central to Galileo's trials. While Galileo definitely didn't do himself any favours via his combative style, the interpretation of the bible and Solar System was definitely central to his trials.

    For details see translations of the original documents (e.g., in "The Essential Galileo").

    A useful introduction is also available at

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  35. Andy @ 33

    If you re-read my post (above) you will see that I said that the way to *start* is to determine what the sustainable population level would be if everyone had the same level as the European middle class. I don't think it's unrealistic to think that the third world would not aspire to that.

    Also, I don't think that bringing down the overconsumption (and who's to define that anyway) of the West to a hair shirt level is (a) necessary or (b) desirable and/or (c) remotely possible by democratic means.

    If a "sustainability study" had been done before the industrial revolution it might (and I'm just playing with numbers here) have come up with a population of say 5Bn. Starting from here and now, with the historical consumption of energy and resources, it might be 3Bn. In any case, I would bet quite a bit on it being well short of 9Bn odd.

    Frankly, efforts to reduce CO² emissions sufficiently to avoid tipping points are not going to work unless population is the prime target, or possibly unless the third world is to be kept at a very low standard of living.

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  36. chrisd3, I have had exactly the same result when using analogies.

    It's not just climate skeptics, but applies to anyone who has a view that can be easily demonstrated to be silly via an analogous concept.


    Another 'tactic' I have seen, is 'forgetfulness' (which may be intnetional or the brain protecting itself from dissonance). I've managed to extract concessions from skeptics at times, and then a week later have them repeating exactly the mantra that they acknowledged was flawed.

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  37. Michael J. I. Brown wrote up at Broken logic:

    "There’s no reason for natural and anthropogenic climate change to be mutually exclusive, and yet climate change deniers frequently use natural climate change in an attempt to disprove anthropogenic global warming."

    ~ ~ ~

    It reminded me of a bit of a dialogue I had going with a contrarian --

    This character insists that: "The null hypothesis, is of course, natural climate change explains all observed climate change." ~~~

    my response: "To begin with this "null hypothesis" doesn't make any sense because if we look at the situation from a geophysical perspective there is nothing unnatural about today's increasing greenhouse gas levels causing our atmosphere's insulation ability to increase, in turn causing our planet to warm.

    It is only the source, human burning of fossil fuels, that is unique in the long varied history of our planet.

    It would be interesting if K or any other science contrarian can suggest a more meaningful null hypothesis, since his is broken." ~~~


    Everything humans do is acting upon "natural patterns" and there is nothing "unnatural" with rapidly increasing greenhouse gases sending the planet's weather system into higher gear.

    We are injecting extra energy/heat/moisture into huge geophysical entities, that we call "patterns" to help distance ourselves from the reality of what our planet's global heat distribution engine is all about. 

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  38. It might be interesting to challenge deniers to try and convince us "warmists" that Co2 in the atmosphere isn't rising by 2ppm per year and the science that proves Co2 creates warming is false. Given that they won't be able to a more revealing question might then be to ask them why they would want to deny something so well proven. All weather forecasters should include current Co2 levels as part of their forecasts. At least that might start a few million people to actually start thinking about the issue. The biggest problem at the moment aren't the deniers, it is the total lack of interest the majority of people have in the subject. Those of us who argue about it are still a minority of the population.

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  39. There's a few strawmen around in this discussion perhaps the most egregious of which are that sceptics/deniers claim there is no climate change and/or all climate change is due to natural causes.  Obviously I haven't met every sceptic/denier but based on the comments from those that  I have, the sceptics/deniers view on climate change is:

    "of course climate change is happening it has been happening since the earth began"  and

    "of course CO2 from the burning of fossils fuels is contributing to climate change in addition to the contributions from natural causes"

    A question  that sceptic/deniers often ask is what percentage of climate  change is due to the burning of fossil fuels.  Various scientific bodies have stated: "Humanity is the major influence on the global climate change observed over the past 50 years." (American Geophysical Union 2013}.  This doesn't of course specifically address burning of fosil fuels aa deafforestation and other activities are covered by this sweeping statement.  Others state "anthropogenic contributions are significant." (American Medical Association2013), "the dominant cause of the rapid change in climate of the past half century is human-induced increases in the amount of atmospheric greenhouse gases", (American Meteorological Society 2012) and the IPCC states "“Most of the observed increase in global average temperatures since the mid-20th century is very likely* due to the observed increase in anthropogenic greenhouse gas concentrations"

    Clearly these august bodies do regard burning of fossil fuels as contributing significantly (as indeed do the sceptics/deniers I have spoken to) but do not put any sort of a figure on how much this contribution is.  Consequently it seems a fair question from sceptics/deniers as to what percentage is due to human activities.  It clearly isn't 100% else unless the roles of the AMO and PDO and other natural factors is nil and taking the change over 50 years may not exclude long term cycles in natural phenomena such as in the NAO and AMO (

    Another question asked by many of the sceptic/deniers I have met is"What is the optimum global temperature?"  Most sceptoics/deniers are aware the global temperature in  the Mediaeval Warm Period may well have been cooler than today but that doesn't answer the question of what is the optimum.  

    Naturally, I expect this post to be classed as trolling and if so, so be it.  But uncritically dismissing sceptics/deniers as trolls is perhaps not justified.

    I don't think that has been answered above.  Other questions are"What is the ideal global temperature

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  40. Ashton @39.

    Good of you to volunteer to role-play for this thread on trolling. In citing Ólafsdóttir et al (2013) as some form of evidence for the existence of "long term cycles in natural phenomena such as in the NAO and AMO" that may or may not have played a significant role in recent warming, did you manage to read it? If not, you may find this bundle of 2 studies useful as it is open access and includes the Hvítárvatn study.

    Also note that the "clearly isn't 100%" message assumes all those devilish natural wobbles don't go and all cancel themselves out, which they probably would do at some point in time, just as they would at times produce a net cooling resulting in an embarrasing +100% AGW contribution.

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  41. Ashton (or the fake skeptics he represents): "What is the optimum global temperature?"

    Optimum temperature for what?

    Before you respond, I'll point out that the question is irrelevant.  It's a rhetorical ploy designed for those who don't understand the central problem with global warming.  There is an optimum temperature range for life on planet Earth.  The danger from global warming is the rapidity of the change in temperature.  Now that you're included in the group the meme targets, perhaps you might want to do a bit more reading before simply acting as a parrot for those who design these sorts of ploys.

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  42. It's isn't the science that's frequently in question.  The argument is about "selling newspapers," "garnering alliances," and individual and social power relationships.  Humans, chimps and baboons do it along with all other primates, and that's the dynamic in play.  For better or worse, factuality is frequently a wallflower in the great social debate.  It always has been.

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  43. In my experience, the Galileo Gambit most frequently arises in the context of the "science doesn't work by concensus" myth.  "The consensus in Galileo's time," trills the troll, "was that the sun went around the earth.  Galileo stood alone against that model."  My response takes a somewhat Socratic approach: "How do you know Galileo was right?  Have you yourself peered through a telescope and done the various orbital calculations?  I'm guessing not.  I propose that you learned he was right by reading science texts, which represent the aggregate opinion of modern astronomers.  In other words...consensus!" 

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  44. Ashton

    In this debate, it is not only the quality of the arguments that are important, it is also the quality of the questions asked. Your question, what is the optimum temperature has no meaning when you consider the temperature gradient across the planet from the equator to the poles, between the hemispheres and between the ocean and the land. Also,  the context of the question is important.

    Perhaps, you need to explain how increasing greenhouse gases are NOT going to warm the planet and change the climate? Also, you need to explain why these greenhouse gases are at least 40% above the norm of the past million years, even through the ice ages and inter-glacials,  particularly since we have seen this increase occur in under 200 years when normally, in the past, such a change would take thousands or tens of thousands of years. Also, you need to explain why we are seeing a change of 2 ppm annually, which again is unprecedented prior to the industrial era? What is different today that these changes are happening  if they are all occurring naturally? Magic or do you think all the scientists who have observed these changes are just fudging the figures? You could also answer, how burning all the known reserves of fossil fuels and increasing greenhouse gas levels in the atmosphere back to the age of the dinosaurs, considering that the Sun's radiance level was at least 10% lower at that time, could possibly be good for the global climate considering that this was the climate that allowed us to evolve into who we are today?

    Answer those questions and show that it is all just natural and then perhaps you will be taken seriously.

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  45. Ashton @39, the GHG contribution to recent warming (since 1950) has been 138% +/- 63% (90% confidence range).  The total anthropogenic contribution has been 108% +/- 19%.  The combined contribution of all non-GHG anthropogenic factors was -38% +/-54%.  Negative contributions indicate that the factor would have cooled temperatures in the absense of other effects; while contributions greater than 100% means that absent some cooling effect, the factor would have caused the warming to be greater than that observed.  The large uncertainties for GHG contribution and Other Anthropogenic (OA) contributions are not independent.  A larger GHG contribution implies a more negative OA contribution, and vice versa.  The PDFs of the three factors is plotted below:

    Like the figures for the total anthropogenic contribution in a recent Real Climate post, these figures are derived from the AR5 WG1 figure 10.5.  There figures differ slightly from mine.  They round the mean estimate of total anthropogenic contributions up to 110%, and give a 90% confidence interval of 80-130% compared to my 89-127%.  I am not sure of the reason for the difference.  It may be due to aggressive rounding of the 95% confidence interval mistakenly attributed (84.7-130.8% by my calculation), or to an error on my behalf.  The difference is not large enough to be relevant for internet discussions.

    This information has been in the public domain now for a year.  Sufficiently accurate equivalent information has been in the public domain since 2007 (AR4).  I do not see any skeptics/deniers accepting their "question" as having been answered.  Rather, I see either concerted efforts to obfusticate (a la Curry) or outright dismissal of the figures because they come from the IPCC.  The reason is simple - it is not an answer that sits comfortably with skeptics'/deniers' ideology. Granted a small percentage of skeptics/deniers may be simply scientifically confused, but polls show that most adhere to a right wing economic ideology - in many cases an extremist right wing economic ideology; and an astonishingly large percentage of their leading lights have direct connections with righ wing think tanks.  By objective measure, it is opposition to the findings of the IPCC that is politically motivated - not acceptance.

    I think this example, chosen by you, shows very clearly that AGW "skepticism" is not based simply on having some relevant questions unanswered.  That is only a plausible supposition if the questions have in fact not been answered.  

    Further, in this case, the straightforward answer of the IPCC that it is 90-100% certain (ie, "is very likely") that "More than half of the observed increase in global mean surface temperature (GMST) from 1951 to 2010 is ... due to the observed anthropogenic increase in greenhouse gas (GHG) concentrations"  is more than sufficient to give mitigating AGW a high policy priority.  Quibling because exact mean and range estimates are not given in executive summaries is plainly an obfusticatory tactic, ie, it is trolling.  This is particularly the case given that the more detailed answer can be obtained by simple maths from that same report.  (I assume that somebody genuinely interested in a more detailed result would do the maths themselves, or at least consult the figure to obtain the mean and 90% range of temperature contribution, which requires no more than a pixel count.)

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  46. On a side note, "ideal temperature" differs by organism, by mass (larger prefers cooler), by metabolism (ectothermic prefers warmer up to about 40 C, endothermic prefers colder), and by specific adaption (polar bears prefer cold, thermophiles prefer hot).  Because different organisms will respond differently to changes in temperature, rate of change in temperature becomes a relevant factor.  For example, trees, ceterus paribus, do better with warmer than typical north american summer temperatures, but beetles do even better still so that the net effect of warming is devestating to trees - at least in the short term.  Consequently rates of change in temperature greater than 0.01 C per century sustained over multiple decades would be net harmfull to ecosystems regardless of whether or not they are net beneficial or harmfull after several thousand years of adaption.

    Given all of the above, the question "What is the ideal global temperature" is too simplistic even assuming it is intended seriously rather than as a rhetorical ploy.

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  47. Mancan18.  A couple of points.  You ask: "Your question, what is the optimum temperature has no meaning when you consider the temperature gradient across the planet from the equator to the poles, between the hemispheres and between the ocean and the land. Also, the context of the question is important".

    Read what I wrote. First let me make it very plain to you I'm not asking the questions sceptics/deniers that I have spoken to are doing the asking.  

    Second I agree there is a range of temperatures.  That being so how can the IPCC or anyone else give a global temperature?  But they do.  Are the satellite measurements giving global temperatures meaningless? In the context you describe, apparently they are.  So can you advise if why, on the one hand global temperatures are reported while on the other you say optimum has no meaning?  If it has no meaning how can decisions be made as to the effect of an increase of, say, 2C will have?  That question also is relevant to the comment by Tom Curtis that "the question "What is the ideal global temperature" is too simplistic"

    But all that aside, my point was that far from being trolls and thickos and dunderheads and lower forms of life, many sceptic/deniers I have spoken to clearly are not.  And Tom Curtis, dissing Judith Curry because she does not agree with you is a bit infra dig.  Does she diss you because you don't agree with her?

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    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

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  48. Ashton,

    It is tiresome enough reading simplistic denialist talking points without the added vexation of having those talking points tossed into the debate by someone who will not then take responsibility for them. If you personally think the question: 'What is the optimum global temperature?' is worthwhile, and more than a distracting rhetorical trick, defend it as your own. If you don't think it is a worthwhile question, please don't give it airtime.

    The diss-worthiness of Curry is a whole extra debate, but it is disingenuous and unfair to accuse Tom, who always scrupulously sticks to the data, of dissing someone merely because they disagree with him. Your own interactions with him should already have been enough to make you realise that. If you knew more about climate science, and more about Curry in particular, you would recognise the remarkable restraint with which Tom describes Curry's position.

    If you do not want to be dismissed as a concern troll, I suggest you stop quoting the ideas of others and stick to comments about the actual data and your own interpretation of it.

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  49. Ashton:

    1)  Judith Curry quotes the IPCC as saying:

    "It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together."

    As the IPCC explains in a footnote that "Extremely likely" means a likelihood of "95–100%".  Therefore the above statement can be parsed as

    "There is a likelihood of at least 95% that more than 50% of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together."

    That is, I put it to you, not at all ambiguous or imprecise.  Further, as based on Fig 10.5 the likelihood of the anthropogenic contribution being 50% or less is 0.000027%(*), and thus that the IPCC statement is extremely conservative given the likilihoods represented in Fig 10.5.

    In response to this, Curry writes:

    "I’ve remarked on the ‘most’ (previous incarnation of ‘more than half’, equivalent in meaning) in my Uncertainty Monster paper:

    Further, the attribution statement itself is at best imprecise and at worst ambiguous: what does “most” mean – 51% or 99%?

    Whether it is 51% or 99% would seem to make a rather big difference regarding the policy response. It’s time for climate scientists to refine this range."

    If "most" is equivalent in meaning to "more than half", than the IPCC statement is not at all imprecise, and it is hardly beneath anybodies dignity to make it clear when a purported authority on a subject takes what is clear and precise and tries to get people to believe it is the opposite.

    (* - My calculation still gives a far more restricted likelihood than does that by Gavin Schmidt at Real Climate - a discrepancy I cannot at present account for. He, however, gives a likelihood of 99.5% that the anthropogenic contribution is greater than 66%, so the difference in no way affects the logic of the argument.)

    2)  The Earth's surface does indeed experience a range of temperatures, and that in no way prevents it from having a Global Mean Surface Temperature (GMST).  Not distinguishing between a mean temperature and a common temperature for all the globe, as you do is some pretty sterling obfustication itself.  Even if we take you to be talking about the GMST, your point is a non sequitur.  If you disagree, I am willing to discuss the point in detail where it is on topic.  

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  50. Ashton: "Read what I wrote. First let me make it very plain to you I'm not asking the questions sceptics/deniers that I have spoken to are doing the asking."

    What Leto wrote. 

    Ashton: "Second I agree there is a range of temperatures. That being so how can the IPCC or anyone else give a global temperature? But they do. Are the satellite measurements giving global temperatures meaningless?"

    Global temp is meaningless as an absolute figure in isolation.  As a time series (and, by extension, the anomaly), it is quite useful.

    Ashton: "In the context you describe, apparently they are. So can you advise if why, on the one hand global temperatures are reported while on the other you say optimum has no meaning? If it has no meaning how can decisions be made as to the effect of an increase of, say, 2C will have?"

    Global mean surface temperature isn't used as anything other than as a time series (note that you use the word "increase").  You're trying to turn a strawman into Godzilla.  It's embarrassing.  

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