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How to be a real sceptic

Filed under: — gavin @ 19 December 2005

Scepticism is often discussed in connection with climate change, although the concept is often abused. I therefore thought it might be interesting to go back and see what the epitome of 20th Century sceptics, Bertrand Russell, had to say on the subject. This is extracted from the Introduction to his ‘Sceptical Essays’ (1928):

I wish to propose for the reader’s favorable consideration a doctrine which may, I fear, appear wildly paradoxical and subversive. The doctrine is this: that it is undesirable to believe a proposition when there is no ground whatever for supposing it true.

First of all, I wish to guard myself against being thought to take up an extreme position. … [Pyrrho] maintained that we never know enough to be sure that one course of action is wiser than another. In his youth, … he saw his teacher with his head stuck in a ditch, unable to get out. After contemplating him for some time, he walked on, maintaining that there was no sufficient ground for thinking that he would do any good by pulling the old man out. … Now I do not advocate such heroic scepticism as that. I am prepared to admit the ordinary beliefs of common sense, in practice if not in theory. I am prepared to admit any well-established result of science, not as certainly true, but as sufficiently probable to afford a basis for rational action.
There are matters about which those who have investigated them are agreed. There are other matters about which experts are not agreed. Even when experts all agree, they may well be mistaken. …. Nevertheless, the opinion of experts, when it is unanimous, must be accepted by non-experts as more likely to be right than the opposite opinion. The scepticism that I advocate amounts only to this: (1) that when the experts are agreed, the opposite opinion cannot be held to be certain; (2) that when they are not agreed, no opinion can be regarded as certain by a non-expert; and (3) that when they all hold that no sufficient grounds for a positive opinion exist, the ordinary man would do well to suspend his judgment.

So does this provide any clarity? Russell clearly doesn’t support an extreme where everything must be continually doubted and nothing can ever be known. As he later suggests, that kind of position would make it philosophically troubling to ever get out of bed in the morning. This extreme attitude does however rear up in climate discussions where an interesting debate on the impacts of human-related increases of greenhouse gases on, say, the atmospheric circulation, often becomes bogged down in how do we know that GHGs are increasing at all, whether they are affected by human activity, and how it’s all down to the sun anyway. Since all of these things have been discussed ad nauseum here, here and elsewhere, that kind of ‘scepticism’ (more accurately described as contrarianism, or ‘la-la-la-I-can’t-hear-you’-ism) serves only to waste time. Since working scientists are all busy people, this is usually why we tend to cease communication with such contrarians very quickly.

If we relax the above-mentioned constraint requiring ‘all experts’ to agree (something never achieved in practice) to ‘the overwhelming majority of experts’, we can substitute in the IPCC for ‘experts’ in the quote. It’s important to note that Russell does not claim that if all experts are agreed, then one must agree with them, but solely that being certain of the opposite opinion in such circumstances is not wise. It is implied by his opening statement then that having ‘all experts’ agree something is reasonable grounds for supposing something to be true. Similarly, if the IPCC concludes that something is highly uncertain (such as the magnitude of changes in aerosol indirect effects), then there are no good grounds for assuming otherwise.

Can someone be productively sceptical? Of course. Firstly, one needs to be aware that scepticism about whether a particular point has been made convincingly is not the same as assuming that the converse must therefore true. Sometimes scientists just don’t use the best arguments they could (particularly if they are a little out of their field of expertise) and these points can, and should, be challenged. One example would be the use of an incorrect ‘correlation implies causation’ argument. For instance, the strong correlation of CO2 and temperature in the Antarctic ice core records does not in and of itself imply that CO2 has a radiative impact on climate. However, additional analyses that look at the factors controlling temperature during the ice ages give strong grounds for believing that CO2 does play an important role. Therefore while the use of the correlation argument alone is wrong, the converse of the conclusion is not necessarily true.

Secondly, it helps to have done the homework. It is highly unlikely (though not impossible) that the sceptical point in question has not already been raised in the literature and at meetings. If a particular point has been argued to death previously and people have moved on (either because it was resolved, moot or simply from boredom), there is little point bringing it up again unless there is something new to talk about. Obviously, a good summary of how the point was dealt with can be educational though. Arguments about whether the current CO2 rise is caused by human activity fall clearly into this category.

Thirdly, scepticism has to be applied uniformly. Absolute credence in one obscure publication while distrusting mountains of ‘mainstream’ papers is a sure sign of cherry picking data to support an agenda, not clear-thinking scepticism. Not all papers get the peer review they deserve (or require) and the literature has many examples of dubious logic and unsupported interpretation. Sometimes this becomes very clear (for instance, the Soon and Baliunas saga at Climate Research), and sometimes it goes uncommented upon. But what about Galileo? Wasn’t he an obscure scientist persecuted by an entrenched mainstream? Yes, but Galileo is celebrated today because he was correct, not because he was persecuted. If an idea is right, it will be supported by additional evidence and will lead to successful predictions – at which point it will likely be accepted. The ‘Galileo’ defence (and its corollary the ‘establishment conspiracy’) are usually a sign that the additional evidence and the successful predictions are lacking.

Finally, it should be understood that constructive scepticism is a mainstay of the scientific method. The goal of science is to come closer to a comprehensive picture of how the real world works, with scepticism essential to toughening up scientific ideas, though alone, it is insufficient to move understanding forward. It isn’t essential that every true sceptic have an alternative theory ready to go, but they should bear in mind that our picture of how the world works, though incomplete, rests on many different foundations. If it sometimes seems that the scientific consensus is resistant to new ideas, it is because that consensus has already been tested in many ways and yet still stands.

Much of what passes for ‘debate’ on climate change in the popular media, is often framed as the ‘scientific consensus’ vs. the ‘sceptics’. A close examination of these arguments (for instance, as outlined in a recent Wall Street Journal editorial) doesn’t reveal much that could be described as true scepticism since they often use the fallacious reasoning that we discuss above. However, since scepticism has a (justifiably) long and noble tradition in science, the framing device is quite powerful (despite the lack of connection with any actual scepticism). As with the intelligent design controversy, agenda-driven opposition has often managed to cloak its contrarianism with the mantle of scepticism. So, while many contrarians pay lip service to the legacy of Russell (or even Pyrrho), forgive me if I remain a little sceptical…

210 Responses to “How to be a real sceptic”

  1. 151
    Pat Neuman says:

    Until Christy has “done the homework”, those allowing his statements to be published are doing an unfortunate disservice to the public and world environment for the future.

    According the NewsTrack link below, John Christy, director of UAH’s Earth System Science Center, said: “It just doesn’t look like global warming is very global,” … “The carbon dioxide from fossil fuels is distributed pretty evenly around the globe and not concentrated in the Arctic, so it doesn’t look like we can blame greenhouse gases for the overwhelming bulk of the Northern Hemisphere warming over the past 27 years” he said. “The most likely suspect for that is a natural climate change or cycle that we didn’t expect or just don’t understand.”

  2. 152
    Maurizio says:

    Re: The original text (William’s?), Dano’s
    145 and Coby’s #146

    This is a posting about methods more than materials

    You do have me worried guys as it appears there are huge misunderstandinds about the basic tenets of the scientific method (including skepticism).

    Is nobody familiar with the Skeptic Society (

    Let’s examine what you’ve been suggesting (as method of skepticism), and why it is so wrong

    (a) Is it logical, wise, appropriate (and scientific) to rely on what the scientists say, and forego skepticism of what the scientists say, as suggested in the original text of “How to be a real skeptic”?

    No. That would be like “leave science to the scientists”, not much different from “leave astrology to the astrologers” (i.e. the rest of us suckers will just have to gobble up whatever the astrologers say).

    And plenty of people (including scientists) pretend to do scientific work that isn’t (Gould’s The Mismeasure of Man is as good a collection of that as any)

    (b) Is it logical, wise, appropriate (and scientific) to “put up or shut up” and sheepishly follow the latest scientific fashion unless one has some alternative explanation, as suggested by Dano at #146?

    Again, no. For example, I do not have an alternative explanation for Feng Shui: why should that prevent me from being skeptical about having to move about the furniture according to imperscrutable “energy fields”?

    And in hindsight, the fact that there was no alternative theory in the mid-XIX-century did not make the existence of an all-pervasive celestial ether any more plausible

    (c) Is it logical, wise, appropriate (and scientific) to “put up or shut up” and sheepishly follow the latest scientific fashion unless one has “studied the issue”, as suggested by Coby at #147?

    By all means, another resounding “no”. I have not studied Homeopathy in great details, and am not following the “state of current research”. Does that mean I have to believe that my health would improve by ingesting chemical solutions so diluted that (at best!) a handful of the original molecules would be present?


    In general, why do you people have so much trouble with skepticism “per se”? How can anybody do anything properly scientific without a skeptical frame of mind? And is it really necessary to be so (hyper-)defensive about human-induced global warming?

    Any and all scientific theories and models must be able to pass some sort of a threshold before being “accepted”.

    I did mention superstrings in physics as a good example of what is not (as yet) a strong scientific theory. It explains lots of physical phenomena but has not been “demonstrated” but with circumstantial evidence.

    In other words, would any supporter of string theory feel offended if I were to say I am skeptical of their models being the underlying basis of reality? Of course not (I hope so!). All people involved are aware of the current limitations and the search for evidence one way or another is not a bit less enticing for that

    There is a debate about string theory. That doesn’t mean they’re rubbish


    I have gone into great detail about global warming, and about its human-induced part. I have described both as “extraordinary claims” and described what “extraordinary evidence” would convince me of the former.

    I have even admitted that (as yet) I do not know what “extraordinary evidence” would convince me of the latter (and no, that does NOT mean that “nothing will convince me”; last time I have checked, it was up to the researcher to find a convincing way to demonstrate their findings)

    It would be interesting to know what convinced you of the “reality” of human-induced global warming

    [Response: You appear to have completely misunderstood the point of the post. The point was to demonstrate that nobody has any problem with scepticism ‘per se’ – what there is a problem with is simple contrarianism disguised as ‘scepticism’. Nobody is asking you to trustingly believe anything just because we say so. The scientific consensus on this issue has arisen because of an increasing body of evidence (the clear signs of global warming (oceans, land, ice), the radiative properties of the undoubtedly anthropogenic changes in atmospheric composition, the match of numerous diagnostics between model results and observations – only if anthropogenic effects are included). There are continuing uncertainties in many aspects of the science (related to aerosols, or the exact value of the climate sensitivity etc.), but they do not negate the likelihood of continued warming if GHG levels continue to rise. I agree that this might seem an ‘extraordinary claim’ – but there are clear physical principles to support this, including experimental data, observations and modelling – something clearly not true for homeopathy or Feng Shui. The test of any scientific theory is its ability to make predictions – model projections made in 1988 did a good job of matching the subsequent temperature evolution, models predicted the cooling to be expected due to Mount Pinatubo, they have correctly hindcast the cooling of the stratosphere, the warming of the oceans, and the temperature evolution of the 20th century. I would indeed find this (and much more evidence that we could get into) pretty extraordinary if it was in fact not a good approximation to what is happening in the real world. There is never absolutely proof in Earth science, but the balance of evidence is certainly heavily weighted to the reality of human induced global warming. – gavin]

  3. 153
    Maurizio says:

    And now a posting more about the details of the topic at hand

    Re: William’s response to #143, Hank’s 144, Dano’s
    145 and Coby’s #146

    1. About past predictions of coming ice ages

    First of all, the fact that scientists in a particular field were “wrong” in the past does not mean they’ll always be wrong. It just means their next set of statements must be quite accurate to recover credibility

    [Response: Coby has answered many of your points below. I’ll repeat on this one, since its my speciality: your “fact” isn’t a fact: its wrong. You are the victim of septic propaganda and inaccurate press reports. Fortunately the truth is available: see – William]

    Second, the problem here is that the contemporary climatologists of the IPCC are pushing for policy changes in society. In that respect, the fact that (rightly or wrongly) society was misinformed in the 1970’s is important indeed. Policies are based on consensus, after all

    [Response: You’re wrong here too. The scientists and the IPCC stick fairly strongly to science. RC, for example, does its best to avoid policy – William]

    2. Kilimanjaro’s 12,000-year-old snows


    etc etc

    Unless of course it’s another case of the lay press overtaking what the scientific journals are saying?

    [Response: Not convincing. The first just says its a 12kyr core. That doesnt mean that there was no snow there 12kyr ago – just that the usable record doesn’t go further. The second is more specific, but I wouldn’t trust it not to be garbled. It was cold 12kyr ago – – William]

    3. About The Economist’s view that climatology is based “on drawing conclusions from patchy information”

    William: It’s hard to comment to statements like “The Economist isn’t a good source for climate science”. Sounds elitist at best. Your blog appears to indicate that you’re stuck in the right-left-wing categories of present-day USA. You also assume that the authors on The Economist are “economist-types”: that is akin to suggest that their rubbish collectors have a PhD in economic liberalism, just because they work at the magazine

    That said, you are right in noting that if the folks at The Economist can’t be convinced, there are huge troubles ahead for the “let’s stop producing CO2” people

    4. About global warming vs. human-induced global warming

    Is it really that difficult to distinguish those 2? I did indeed describe what would convince me that extraordinary global warming is going on at the moment: something more tangible than “the temperature is going up”. Something like an incontrovertible change brought upon us by that increasing temperature. Why e.g. have the monsoons not shifted? Is that not a valid question to ask?

    Do I really have to explain why that is different than measures of shrinking glaciers, and (patchy) measures of ocean currents?

    5. About “So your answer is damn the torpedos, full speed ahead?”

    Uh? didn’t I write “I am all for free speech and free thinking, so go ahead, and campaign to sequestrate CO2 and reduce the use of coal as fuel. But please don’t dress it up (yet) as ‘hard science'” ??

  4. 154
    Coby says:

    Maurizio, you are right that a good sceptic is unafraid to ask the questions. But they need to listen to the answers and you have obviously not listened to the very clear evidence William showed you or you would not continue to think that a large consensus of the climate science community was urging action to avoid an ice age in the ’70’s.

    Statements like “The Economist isn’t a good source for climate science” sounds like common sense to me, hardly elitist. Real Climate is not a good source for economics either. No put downs there!

    Is it logical, wise, appropriate (and scientific) to “put up or shut up” and sheepishly follow the latest scientific fashion unless one has “studied the issue”?

    I don’t know if you are very young and overly proud or what, but, with a small substitution: yes absolutely, it is logical, wise and appropriate to heed the advice of experts unless one has studied the issue.

    5. About “So your answer is damn the torpedos, full speed ahead?”

    Uh? didn’t I write “I am all for free speech and free thinking, so go ahead, and campaign to sequestrate CO2 and reduce the use of coal as fuel. But please don’t dress it up (yet) as ‘hard science'” ??

    Yes, but I took that (perhaps incorrectly) as “you have fun advocating, I’m gonna wait this one out”. Which in the domain of climate change mitigation means “full speed ahead”. And I reiterate, the longer you are insisting on some undefined incontravertible evidence before ceasing actions that by all evidence will drastically alter our climate, the worse odds we have in this irresponsible gamble where future generation’s ability to thrive is at stake.

    The rest is going around in circles except for your offer to explain the high stock you would put in a change in the monsoons. Why is that so much more convincing than:

    – glaciers all around the globe melting
    – arctic sea ice declining:
    – ancient permafrost melting
    – coral reefs bleaching and dying
    – hurricane intensity increasing

    and many other anecdotal and regional reports of climate change that are out there. What is special about the Sahara desert and the monsoons?

  5. 155
    Dano says:

    Maurizio wrote (current 152):

    In general, why do you people have so much trouble with skepticism “per se”? How can anybody do anything properly scientific without a skeptical frame of mind?

    First, “you people” isn’t a good start. Second, no one here has a problem with skepticism (as Gavin said).

    What _I_ said wrt your second sentence I italicized was that you people – the septics – (note the spelling) have no properly scientific anything. Nothing. Nada. You people can’t argue your scientific position because there is none; just saying something over and over doesn’t make it so.

    There is nothing that shows today is part of a natural cycle and thus nothing to worry about – no attribution here, therefore no tobacco-like lawsuits, move along now – and I challenge you people to take your properly scientific skepticism, develop a testable hypothesis, collect some data, analyze it, write it up, and let us know what you found. When there are some results out there, then a model can be built based on physical principles and the data you and others collect can be fed into it and the model to try to get an idea of what is happening.

    As the CO2 levels in the atmosphere are unprecedented in likely the last ~650 K yr, I’m sure a lot of folks will be very interested in your results. I’m sure there is a lot of funding out there for research to show this is just a natural cycle. If you need some help writing up the grant request, let me know.



  6. 156
    Hank Roberts says:

    Applauding Gavin’s response, at the bottom of 152, beginning
    > [Response: …

  7. 157
    Maurizio says:

    I clearly posted a comment about the METHOD of skepticism and Gavin replied about the MATERIALS of human-induced global warming. And just read Dano’s contribution (written, perhaps, without reading my comment in full) to understand what I mean when I say that some people DO have problems with ANY skepticism

    May I assume then that all my points about skepticism, the Skeptic Society, etc are still unanswered?

    Not to mention the fact that I tried to move the “70’s Ice Age” debate from the incorrect reporting about Climate Scientists at the time to the obvious consequences at a social level for the huge misunderstandings propagated by Newsweek, lots of popular scientific press, National Geographic, (and may I dare say, very little wisdom in some scientific articles’ titles).

    Let’s try again


    Is anybody willing to take up my “monsoon” challenge?

    What’s so wrong in asking for incontrovertible evidence to global warming?

    Everything else we do have (“glaciers all around the globe melting; arctic sea ice declining; ancient permafrost melting; coral reefs bleaching and dying; hurricane intensity increasing”) MAY be interpreted as evidence of (unprecedented/unnatural/runaway) global warming, and is COMPATIBLE with the idea that the world is getting extraordinarily warmer…but is there really any serious scientist out there that says “unprecedented/unnatural/runaway/extraordinary global warming” is the only way to interpret those data?

    For example: how does our current CO2 level compare to, say, catastrophic events in the past? What was the CO2 level, and the yearly increase in the atmosphere, when supervolcanoes were making the Deccan Traps? Is there evidence for coral bleaching at the time?

    It would be all very different if we were to witness a clear, unprecedented change in any weather pattern

    (The people at The Day After Tomorrow clearly understood that point…they didn’t depict a little less ice here, a little more sea there, with a dead coral in-between: they could only justify the disaster with continent-size temperate-area “hurricanes”)

    And by the way…I thought the South Atlantic hurricane were that “clear, unprecedented change” (how’s that for being skeptical but not asking for the impossible?), but unless there is a couple of sustained seasons, my jury will still be out.


    Likewise, the models appear to indicate that there is a strong human-induced change in the climate. Obviously I am not contesting that

    But no model, and no statistical correlation, can be enough to justify the acceptance of what remains an extraordinary claim (extraordinary, as already indicated, because we do not control the energies for planetary engineering)

    It would be nice/interesting/precious/indispensable to have something else too, where to base one’s conclusions upon. Is there?


    It’s rather unfortunate that Global Warming is usually presented just as an increase in temperature. If something extraordinary is happening, more than one extraordinary consequence SHOULD be out there for all to see

  8. 158
    Pat Neuman says:

    re 157 Minneapolis is currently experiencing an unprecedented warm weather pattern, as are many other locations throughout the Upper Midwest. Meteorologists on TV stations are asking what the heck is going on. Meteorologist in the federal government continue their silence, claiming that climate change is much too complicated and controversial for their involvement in attempts to help the public understand what’s happening. Climatologists funded by state agencies continue to be silent about this deadly subject, leaving the subject entirely to experts in climate change, who ever or where ever they might be. Climate change continues to be a joking matter in Minnesota.

  9. 159
    Hank Roberts says:

    > asking for incontrovertible evidence ….
    You need a source you trust beyond doubt, to get that, don’t you?

    > how does our current CO2 level compare ….

    You can look this up — and decide whether you trust the answers you find, after reading carefully. But for example —

    I tried Google just now using your words and found this almost immediately:

    From which I’ll pull a bit, but urge you to go to the source and read:

    “The global warming of 55 million years ago, known as the Paleocene/Eocene Thermal Maximum (PETM), emerged in less than 5,000 years, an instantaneous blip on geological time scales (the researchers indicate that 5,000 years can be considered an upper limit and they believe the warming could have unfolded much more quickly than geological records can show them).

    “In the paper, the authors note that modern carbon dioxide input from fossil fuel sources to the earth’s surface is approaching the same levels estimated for the PETM period, which raises concerns about future climate and changes in ocean circulation. Thus they say the Paleocene/Eocene example suggests that human-produced changes may have lasting effects not only in global climate, but in deep ocean circulation as well.

    …. “The case described in this paper may be one of our best examples of global warming triggered by the massive release of greenhouse gases and therefore it gives us a perspective on what the long-term impact is likely to be of today’s greenhouse warming that humans are causing.”

    But don’t trust me or simple summaries. Look this up and consider the sources.

  10. 160
    Tom Fiddaman says:

    Re 148

    It is obvious that the Kyoto proponents don’t believe that we are experiencing severe climate change due to the current level of CO2. If they did, their support of such modest reductions embodied in the Kyoto treaty just wouldn’t make any sense. So, if they are skeptics, can you blame me?

    This doesn’t follow at all. Kyoto is a compromise, not a mandate imposed by GW believers. That it exists at all is due to the strong urgency felt by some, in the face of US resistance. It’s watered down by the need to bribe incumbents to participate, not by nonbelief. And in any case no one expects to be experiencing severe climate change yet – it’s about the future.

  11. 161
    Dano says:

    RE current 157:

    What’s so wrong in asking for incontrovertible evidence to global warming?

    There’s nothing wrong in asking for it. This is planet earth, however, and verrrrry few things are incontrovertable. It’s just not how things work. Science is about likelihoods, not incontrovertable facts. For example, you may ask for incontrovertable evidence that the planet is 4.5 BYO. We don’t have it. But we operate on the likelihood this is true. Oil drillers don’t ask for incontrovertable evidence before drilling – they take the info from their geos and form likelihoods and work from that.

    It would be all very different if we were to witness a clear, unprecedented change in any weather pattern

    There’s nothing wrong in wishing to witness it. This is planet earth, however, and verrrrry few things are clear and unprecedented.

    t’s rather unfortunate that Global Warming is usually presented just as an increase in temperature.

    Correct, except that it isn’t. A simple Lexis-Nexis search should disavow you of that assumption. Maybe that was true 5 years ago, but not today. Check it out.



  12. 162
    Hank Roberts says:

    One big question is the “sensitivity” — how much temperature change happens with a given change of greenhouse gases.

    I _think_ I can paste in Google Scholar links and they’ll work for others. I’ll try here.

    Here’s one cite for an estimate of sensitivity — it’s the range of uncertainty that’s worrisome, because even the low end is not much below 2 degrees, if I”m reading it correctly — (PDF, or view as HTML):

    Here are the search results for the 48 papers that reference the one above — simply reading the titles and brief Google search output will give a fair feel for this.

    But I defer to the climate scientists to comment on the science. I’m just pointing to how to look for information that may at least help us nonscientists ask intelligent and informed questions, by reading up a bit first. I’m reading these …

  13. 163
    Hank Roberts says:

    P.S. — the above is an example of how I look for info before asking questions. If you want to discuss the _content_ of the example, there’s an active thread for climate sensitivity here:

  14. 164
    Pat Neuman says:

    Author of 157 said: “It would be all very different if we were to witness a clear, unprecedented change in any weather pattern”. I replied (158) that Minneapolis and the rest of the Upper Midwest is currently having an unprecedented warm weather pattern.

    Annual Temperaturess at Minneapolis (1820-2005, 126 years of record.

    1. With 2005 annual temperature, a new highest ten year average temperature (46.6 F, 1996-2005) has beaten the old high ten year average (46.4 F, 1930-1939) by 0.2 F. See:

    2. 2005 was the eighth year in a row with above average annual temperatures, the longest warm streak in 126 yrs of record. Previous high number of consecutive above normal annual temperatures was seven set in 2004, …

    3. January of 2006 may be starting off with the warmest temperature pattern of record for this early in the year. What are the meteorologists and state climatologists saying about this. Nothing that might be getting on TV or radio to the public. Most people in Minnesota this string with no end of mild winters. Pay back time will be progressively hotter and more humid summers for years, decades, centuries … ahead.

    4. Snowmelt runoff studies show strong trends for earlier spring snowmelt runoff in the Upper Midwest.

    The weather/climate pattern going on now here can be called rapid hydrologic climate change in the Upper Midwest.

  15. 165
    Pat Neuman says:

    re 164

    Correction, should be 186 years of temperature record at Minneapolis.

  16. 166
    joel Hammer says:

    It is easy being a skeptic because so much nonsense is published about global warming. The real scientists don’t debunk the junk, so the skeptics do and convince people like me that there is great exaggeration about the effects of changing CO2 from 280 ppm to 360 ppm. Anybody care to remember the great drought in the Sahel, which was taken by many as due to human induced global warming? Or, shall we just move on?

    Same old pattern. Alarmists look at the short term and declare disaster a’coming. More sober people take the long view and say this has all happened before.

    Time goes by and the problem just fades away but the alarmists find something else to worry about.

  17. 167
    Hank Roberts says:

    We have to remember — weather is not climate, and vice versa.

  18. 168
    joel Hammer says:

    My favorite professor in school, who was a real skeptic and was proved right in some very important ways years down the road, when he was told he was going against expert opinion, snorted and said:

    “Experts? Those are the guys who tell you we used to make mistakes, but, we don’t make mistakes anymore.”

    Guys, listen to yourselves.

  19. 169
    Dano says:

    Although weather data eventually become climate data, Hank.



  20. 170
    Lloyd Flack says:

    It is much easier to have incontrovertible evidence of trends and states than it is to have incontrovertible evidence of causal connections. To get the latter one generally does experiments where one can control the conditions. If all the conditions except one are the same in two cases and the outcomes are significantly different then one can reliably infer that the changed condition caused a change in the outcome. We can’t do such an experiment on climate change so we have to take other approaches.

    We have to answer three questions. Has there been global warming over the industrialised period? Have greenhouse gases increased over this period? If there has been global warming and greenhouse gases have increased has the increase in greenhouse gases cased the warming?

    The warming trend is small by comparison with the noise in the data. Nevertheless we can reliably say that the World has been warming. We can extract the signal from the data. Furthermore it has shown up in too many data series at too many places – surface temperatures, Tropospheric temperatures, oceanic temperatures, glacier retreat. Since the Tropospheric data was reexamined and the ocean temperature trend analyses were made the case for global warming became incontrovertible.

    The glacial cores provide incontrovertible evidence of anthropogenic increases in greenhouse gases.

    The problem is with getting incontrovertible evidence that the greenhouse gas increases have caused a large proportion of the temperature increases.

    Physics tells us that if we increase greenhouse gases we will warm the planet. The question is by how much? Will feedbacks increase or decrease the warming? For anthropogenic global warming to be negligible we need to have negative feedbacks nearly as great as the warming effect itself. How do we find out whether we have positive or negative feedbacks and how big are they?

    I do not think that we can conclude just by looking at the temperature data that the temperature increase over recent decades does not have a natural cause.

    All we can do is create mathematical models incorporating the major forcing variables. They have to be compatible with what we know of the physical processes involved and with the historical record. While these models have many adjustable parameters most of them seem to give similar results. Rather like the way you can often fit various regression models with different parameters which end up giving almost the same predicted values. I suppose it’s a bit like creating models of processes in stars.

    The fact that multiple models give similar predictions and fit the historical data reasonably well suggests to me that the predictions are likely to be reliable ones.

    No one has created a model using known physical process and structures that does not show a high sensitivity to CO2 concentrations. Of course something could be going on that we don’t know about that would reduce the effect of increasing CO2. But we have no reason to believe that such a process exists and so by Occham’s Razor we reject such speculations.

    So the preponderance of evidence is that a major part and probably most of recent global warming is due to anthropogenic increass in greenhouse gases. Yes, it is concievable that we have missed a major feedback process that would eliminate most of the effect of increasing CO2. But there is no reason to believe that we have. It is up to greenhouse skeptics to come up with concrete possibilities rather than make hand waving claims about unspecified natural cycles. What are these cycles and what is the evidence for them? The existing models are compatible with the data and do not need any unknown processes with major effects

  21. 171
    Pat Neuman says:

    re 164 165

    11 Jan. 2006
    History and Climate Change at Minneapolis, MN, and Wisconsin

    You may view the article above, which shows 1820-2005 annual temperatures at Minneapolis, by going to the public Madison Independent Media Center website, at:

  22. 172
    Coby says:

    #170 – Lloyd Flack

    Very nicely written!

    Of course something could be going on that we don’t know about that would reduce the effect of increasing CO2. But we have no reason to believe that such a process exists and so by Occham’s Razor we reject such speculations.

    (You mentioned what I am about to, but I wanted to pull it together with the above quote)

    Not only does one need some unknown process whereby CO2 is prevented from warming the atmosphere, but sceptics of AGW need another unknown process that is then driving an alledgedly natural warming that we do in fact observe. I think the need for one major, but completely undetected, factor would put the ball well into the sceptics court to come up with a theory. But having two such unknowns makes it very difficult to even take the notion very seriously.

    (Considering the unique case of climate science and economic implications, it behooves us as global community to check it out anyway. But I think we have.)

    CO2 *should* warm the atmosphere. CO2 is going up, the temperature is going up. This simple reality is why I consider the onus for extraordinary evidence to be much more on the denialist’s side of the debate. Besides, there really is alot of extraordinary evidence already soundly behind AGW theories.

  23. 173
    Maurizio says:

    Pat (158, 164): A series of slightly-warmer winters can not be counted as extraordinary evidence of a change in weather patterns. What happened between 1930 and 1939, and what happened in 1940 to break the series of highs? And we are talking .2F, surely that’s not enough to make flowers appear in January where 20 feet of snow was the norm?

    Hank (159): That study is quite re-assuring, actually, as plants and animals thrived after the PETM. Also, Wikipedia in its infinite wisdom appears to suggest the culprit was massive methane release, not CO2.

    Somebody should advocate the prohibition of using beans as foodstuff! (joke)

    Dano (161): Is it really that much to ask for the ONE weather pattern that has changed due to “global warming”?

    Joel (166): I agree wholeheartedly. If only the Climate Science community would learn to differentiate itself from the “alarmists” and scaremongerers!

    If Human-induced Global Warming is found out to be a mistake like Phrenology (only, more honest), the impact on Climate Science and science as a whole would be very hard to recover from

    Lloyd (170): I could get along with the statement that “the preponderance of evidence is that a major part and probably most of recent global warming is due to anthropogenic increass in greenhouse gases“.

    Still, there must be a plethora of consequences for that: the fact that my “monsoon challenge” remains unchallenged may indicate that we are indeed “missing a major (not necessarily feedback) process that would eliminate most of the effect of increasing CO2

    Look for example at the news that forests may be releasing much more methane than anticipated. Perhaps we are living in a world where the amount of atmospheric CO2 is irrelevant to climate change, in the presence of certain levels of other greenhouse gases (and ice-house atmospheric components)

    Coby (172): We are still back to square one about the methods of skepticism. A Skeptic does not need to come up with alternative scientific models and/or theories.

    The “job” of the skeptic (and everybody should be a skeptic at heart, at least in the scientific community) is to point out flaws in reasoning, absence of or poor evidence supporting a theory, and in general to challenge a theory or model by asking for its consequences to be clear for all to see.

    I may be wrong, but I don’t think Einstein was incensed by the fact that Relativity had to “pass” the 1919 eclipse test by Eddington, and quite a few more eclipse tests before really being accepted

  24. 174
    Pat Neuman says:

    re 173 said – And we are talking .2F, surely that’s not enough to make flowers appear in January where 20 feet of snow was the norm?

    The part that’s significant is that for all ten year averages of annual temperatures 1820 – 2005, 186 years of record, the 1996-2005 average was the highest. Although only by 0.2 F, a 10 year moving average trend appearing as it does over the last 30 years, is unlikely to fluctuate of decrease. Instead, other observed changes in the worlds ice, warming oceans and soils, mean there will likely be an acceleration in the 10 year moving average warming trend, indefinitely, which also means doom to many species.

  25. 175
    Hank Roberts says:

    > 173
    If you find the PETM event reassuring, I find that utterly astonishing.
    Excuse me, but that’s inadequate. It sounds like someone’s feeding you misinformation and you aren’t checking it. Where did you find this so-called reassurance?

    Wiping out the existing biota and leaving a wasteland in which new species can find opportunities did work for us mammals, assuming you are reassured by evolution.

    But it wiped much of the surface of the land off (“weathering”) and washed it into the ocean. That’s why there was such an opportunity. The old regime was washed away and ended up in the ocean sediments, where it was found in ocean drilling.

    Who are you quoting? I’d like to know where you get the reassurance.

    Here’s one description I recommend as a start. Note the warming in that event — it’s not a lot more than we’re looking at currently as possible.


    “In terms of the rate and degree of warming, the PETM is unprecedented in Earth history. Isotope records suggest that at 55 Ma the deep-sea and high-latitude oceans warmed by 4° and 8°C, respectively, in a period of <10 k.y. (Fig. F8). This period of extreme warmth, which lasted <150 k.y., triggered profound changes in global precipitation and continental weathering patterns (e.g., Gibson et al., 1993; Kaiho et al., 1996; Robert and Kennett, 1994). The PETM also affected biota on a global scale, triggering both rapid turnover of benthic and planktonic organisms in the ocean (Kelly et al., 1996; Thomas and Shackleton, 1996; Thomas and Ward, 1990) and a sudden radiation of mammals on land (Clyde and Gingerich, 1998; Koch et al., 1992; Rea et al., 1990).”

  26. 176
    Maurizio says:

    Re: 175

    An “unprecedented warming in Earth history” ends up with species thriving in the new environment.

    If you don’t find that reassuring, I find that “utterly astonishing”.

    For me it’s just more evidence that whatever we humans will punch or pull on the environment, the natural world will simply adapt and thrive

    And that’s truly reassuring

  27. 177
    Coby says:

    For me it’s just more evidence that whatever we humans will punch or pull on the environment, the natural world will simply adapt and thrive

    This is very true. Likewise, whatever toxic waste we dump into rivers and groundwater supplies, it will eventually dissipate, breakdown, dilute what have you. We can also make as big a pile of nuclear waste as we want and eventually it will be safe to walk on it again.

    But unless one is a true sociopath, how is it possible to think that that makes creating those messes ok, and the generations of people suffering through them, waiting until that blessed day comes when nature finally finishes cleaning up, just don’t even rate a second thought?

    This is an utterly self-serving position to take.

  28. 178
    Dano says:

    Re 175:

    For me it’s just more evidence that whatever we humans will punch or pull on the environment, the natural world will simply adapt and thrive…And that’s truly reassuring

    Your conclusion is based on the premise that ‘thrive’ is true. And that’s truly not reassuring.

    At the very least you should name a time scale, as ‘good’ on a geologic time scale is far different than on a human societal time scale [scale is fundamental in ecology].

    (and re 173: your modifiers in were clear and unprecedented, thus my response. Note the difference in wording between bolded 157 and 173, a clue.)



  29. 179
    Dano says:

    Coby and I have not collaborated in the making of our comments. But his point about scale is perspicacious and well done.


  30. 180
    Hank Roberts says:

    Maybe we agree. I find this reassuring, on a geological time scale –and cautionary, on the human time scale:

    “…’What did you do about the dinosaurs?’ he demanded. ‘Did they annoy you? How did you fix them?’ …”

  31. 181
    Kenneth Blumenfeld says:

    Someone said it before, and I’m too lazy to figure out who, since I just read the last 45 posts, but I don’t think Maurizio can be satisfied. Extraordinary evidence? “The Day After Tomorrow?” If you need Hollywood action to convince you, then I guess yes, you will definitely enjoy the coming decades.

    As for a not-so-extraordinary process: the conditions Pat described have been due to an increase in split jet streams over the upper midwest (among other synoptic/dynamic explanations). If indeed that is because of global warming, then there is one weather pattern for you. For excitement, Minnesota experienced its latest 100-year rainfall on record this year, after setting dewpoint and maximum low temperature records also. You would have had to go up to the rural St. Croix river valley to see the worst of it, but if you just imagined a city of 300,000 there instead, then maybe you can have some of the carnage you are after.

    (I know, you can’t pin a single event on global warming. But you can observe that late-and-early-season extreme rainfall events are happening more frequently. I do wonder what that’s all about.)

  32. 182
    Maurizio says:

    Coby (177): It is the second time you try a straw-man argument on me. I don’t think we should mess about the planet “because it’ll be alright in the end”. And I never wrote anything of the sort. I am just glad that there is no indication that our actions can sterilise the planet

    Dano (178): Please don’t try to second-guess me, it’s a waste of time. It is true, I have not repeated “clear and unprecedented” in 173. I don’t see why I should necessarily have done so: a few lines above in 173 I asked Pat about extraordinary evidence, for the umpteenth time. If that’ll make you happier, let me rephrase my question to you: Is it really that much to ask for the ONE weather pattern that has changed clearly and without precedent due to “global warming”?

    Hank (180): haven’t read that story yet but thanks for understanding my point

    Kenneth (181): You haven’t read the messages. Here’s how I can be “satisfied” that there is a dangerous “global warming” going on at the moment: find me a weather pattern that has changed clearly and without precedent.

    Examples are: monsoons shifting (north, east, west, south, you decide); repeated rainfalls in dry deserts; jet streams disappearing from one area and/or appearing in another; sustained hurricane seasons in areas previously seldom touched, like the South Atlantic; january flowering in northern Siberia; year-long ice-free opening of the Northwest Passage, with little or minimal iceberg and sea-ice threat. Etc etc

    It’s really only a matter of imagination. My reference to Hollywood was simply that even the director and writers of TDAT understood that either something clear and unprecedented happens to the weather, or “global warming” will always remain a matter of debate and belief

    I am skeptical of global warming, but I am even MORE skeptical that global warming somehow would not be able to clearly CHANGE a single weather pattern

    I do have a problem with my skepticism, and that is that (as yet) I cannot find how to tell between human-induced and “natural” global warming. But as I wrote twice already, I am open to suggestions, as long as they go beyond the “it can’t be a coincidence”

    [Response: What you’re using here is argument from personal ignorance. Which is unconvincing. If you want a specific non-temperature attribution paper, then you can have Gillett et al, Detection Of Human Influence On Sea – Level Pressure. NATURE 422 (6929): 292-294 MAR 20 2003. If you’re interested in detection and attribution in general, then the IPCC report is probably the best place for a general info and refs to the literature: chapter 12 – William]

  33. 183
    Dano says:

    Re 182:

    You did it again. Science is probabilistic. You seem to be asking for incontrovertable proof, and folk are responding to you like you are. Your phraseology is one that quibblers use to pooh-pooh away evidence. You see this tactic all the time, in public health, in agriculture, in AGW. Note: I’m not saying you are purposefully doing this.

    So, when I say in response you your ‘weather pattern’ question: earlier spring in US Northeast, quibblers say: blablabla not clear evidence yadayada. That’s the game, and why folks are replying to your posts in this way.

    There. Earlier springs/shorter winters in the US Northeast [1., 2., 3., 4., 5.].



  34. 184
    Hank Roberts says:

    A Conversation with Kerry Emanuel
    With Findings on Storms, Centrist Recasts Warming Debate

    “I predicted years ago that if you warmed the tropical oceans by a degree Centigrade, you should see something on the order of a 5 percent increase in the wind speed during hurricanes. We’ve seen a larger increase, more like 10 percent, for an ocean temperature increase of only one-half degree Centigrade.

  35. 185
    Lloyd Flack says:

    Re 173 Maurizio

    I’m slightly confused. Are you looking for unequivocal incontrovertible proof of the warming trend itself or proof of its being caused by human activity.

    You seem to be looking for a simple dramatic demonstration of the effect of global warming that you can use as a proof of its reality. I think the problem is that most climate scientists don’t see things such as you are looking for as proof of global warming trends at all. They see them as illustrations of the effects of global warming but dramatic events tend to be rare events and are not good evidence of trends. To connect, say cyclones in the South Atlantic, with global warming we need explanations connecting the two events. One might conceivably be able to come up with alternative explanations of the events that you are looking for. Yes I think that climate scientists can come up with dramatic changes that are a result of global warming. Attributing them to global warming is more difficult.

    The evidence for trends in global average temperatures comes from thousands of temperature measurements taken at many locations around the world. This is very noisy data and one has to do a lot of work to extract the signal from it. But now we have very strong evidence of increasing trends in surface temperatures, in Tropospheric temperatures and in ocean temperatures. These are incontrovertible proof of global warming. They are the best available kind of proof since they are direct measurements of the temperature itself. Unfortunately they aren’t simple or dramatic or easy to interpret. This is the nature of the beast. They are measurements of trends where there is great natural variability both from region to region or from year to year. But they are actually better proof of global warming than the things that you are asking for.

    If you are looking for proof that anthropogenic increases in atmospheric CO2 have driven global warming then the incontrovertible proof that you want is not possible. This is because we cannot do experiments. We only have data from observations on conditions that we cannot control. All we can do is create the simplest explanations that we can which are compatible with what we know of the physical processes involved and with the observed data. We then make predictions from these models and look for observations that can be used to test these predictions. The current models while hardly simple are compatible with the physics and the observations and take account of all the likely forcing variables. There is no need to introduce unknown processes to explain the observations. Greenhouse skeptics now have to come up with detailed alternative models to be credible. No such models have been created.

    The temperature record was not unequivocal until August last year with the reinterpretation of the Tropospheric temperature data. I did not have a lot of confidence in the climate models until they took natural forcing variables such as Solar variation and volcanism into account.

    Unfortunately global warming is a messy problem. The proofs of global warming are similarly messy. I have to agree with Dano (161) on this one.

  36. 186
    Maurizio says:

    William (183): Thank you for those links. I don’t think a question like “How can I distinguish human-made from natural global warming” is really a way to argue using one’s “ignorance”

    Dano (182): I am sorry that you don’t want to read my messages in full. Far from pooh-poohing any evidence, I have even written that “I could get along with the statement that the preponderance of evidence is that a major part and probably most of recent global warming is due to anthropogenic increass in greenhouse gases“.

    If you and all others agree that there is NO incontrovertible evidence (as yet) for Human-made Global Warming, well, what’s wrong with me saying “I am all for free speech and free thinking, so go ahead, and campaign to sequestrate CO2 and reduce the use of coal as fuel. But please don’t dress it up (yet) as ‘hard science’” ???

  37. 187
    Dano says:

    Re 186:

    If you and all others agree that there is NO incontrovertible evidence (as yet) for Human-made Global Warming, well, what’s wrong with me saying…

    If you want to believe that hard science – which is probabilistic – can make your world incontrovertable, then there’s nothing I can do for you. Sadly, I am unable to reduce my argument to monosyllaby as an aid to clarity and understanding – I simply lack those skills. You may want to read Lloyd’s 4th para in 185 a few times, as it succinctly bounds the issue. William, though, hits upon the ‘economy of phrase’ prize in the first sentence of his response to you in 182; it is the heart of the matter and the reason why I will now wish you well, Maurizio, in your quest for knowledge.



  38. 188
    Coby says:

    Maurizio, I think you would be hard pressed to find any scientist who would say that there is incontrovertible evidence for Antropogenic Global Warming. But the fact that you are still stuck on this only means you have not yet understood that there can never be incontrovertible evidence. If statistical correlations, sophisticated models and internally consistent theories that explain all of the available evidence is not enough for you, then you will, by your own choice of metrics, you will never be convinced. It does not matter how hot it gets, or how many weather patterns change, the proof you seem to ask for does not and can not exist in earth sciences.

    Thus, a person holding out for such proof is not a sceptic in any respectable sense, this is just denialism.

    I asked you before what was special about monsoons and the sahara dessert such that a change there is incontrovertible yet the rapid retreat of glaciers world-wide is not, and I do not recall seeing you address this. The sahara has not always been a dessert, so if it is one day again not a dessert, how will you know that is the result of AGW?

    I know you took exception to this comment before, though I am not satisfied you were right to, but I repeat: faced with the dangers that the best science warns of, based on very voluminous and consistent evidence, it is utterly unacceptable to say “prove it” and tacitly or explicitly endorse a “damn the torpedos, full speed ahead” social policy.

    That’s one hell of a gamble with something unique, priceless and not ours to damage.

  39. 189
    joel Hammer says:

    I notice that people have “moved on” or away from the great human induced drought in the Sahel.

    This simply proves my point. If something is inconvenient, in this climate debate people just ignore it. Going back to my favorite professor, a great quote from him was:
    “Facts are always friendly.”
    Not in this debate.

    A quote from Mark Twain:

    There is something fascinating about science.
    One gets such wholesale returns of conjecture
    out of such a trifling investment of fact.

    And to think, he noticed this before the advent of computer models.

  40. 190
    Hank Roberts says:

    Joel, in your Sahel posting, for me, the latter two links required a login, that you didn’t provide; the first led only to an abstract — membership needed to read the actual article. Hard to comment given only that much.

    Did you mean to illustrate aspects of skepticism? You didn’t say what you thought the links stood for.

    I’m skeptical (wry grin) that people’s lack of response to your Sahel posting in this thread supports your conclusion that people won’t discuss “inconvenient facts” about climate.

    The Sahel drought’s been discussed for decades. I recall it being discussed in geology classes I took back before continental drift was accepted — that was in the late 1960s. Explanations have changed quite a few times since then!

  41. 191
    Maurizio says:

    Coby (188): You still seem to think I am on mission to turn the planet into wasteland. I am not.

    This thread is about “how to be skeptical”.

    I have simply explained why and how I can be skeptical within a scientific framework.

    Ironically, it’s now you saying there is “no incontrovertible evidence” for Human-induced Global Warming: I’d just content myself with the list posted @ 182

    Going back to what’s special with a shifting monsoon, etc, it’s that for the FIRST TIME we would witness a CHANGE in a weather pattern THAT IS NOT JUST a change in intensity (a change in intensity being ipso facto hard to de-couple from a freak phenomenon or some long temporal cycle)

    Perhaps there is scientific literature about why no weather patter has been changing so far. Or perhaps there are peer-reviewed articles about which weather patterns have been changing already.

    My esteemed colleagues of thread are very welcome to point me in the right direction!

    Can we all agree that if global warming continues as predicted, there WILL be changes to weather patterns?

    And by the way: if you want an example of scientifically incontrovertible proof, read about Einstein’s theories and Eddington’s (and later) observations of shifted star positions during solar eclypse

    After all, in brain science people publish scientific articles after scanning a handful of people, but in social science nobody can pass the reviewers without a robust sampling of the general population

    And therein may lie the difference between what is, and what is not (as yet) “hard science”

  42. 192
    Maurizio says:

    Lloyd (185): Somehow we agree on the reasoning, but not on the conclusion.

    For me it’s a matter of “messy data” getting demonstrated by something you define “dramatic”. I agree that the reconciliation of the Tropospheric temperature measurement sets is “a step in the right direction”. For you it was enough…my jury is still out!

    (thank you Dano for pointing me to that comment, I had missed it earlier)

  43. 193
    Dano says:

    RE 189:

    joel, perhaps your argument lacks cogency.

    For example: what are you inferring? Your words are arranged and expressed such that it appears you want to say because someone was wrong once everyone is always wrong. That is what I get from your words, and why I ignored your comment. Perhaps you can restate your argument for clarity.

    Perhaps you wish to say that tree rings as proxy data are not OK as evidence, even as used in a paper way back in 1978, presumably before CO2 fert issues in the record. Perhaps you wish to state the NVDI record is too short to use for evidence, hence more study is needed. Or perhaps you are pointing out that human activities on marginal lands lead to desertification, which exacerbates natural cycles. Or that CO2 doesn’t cause desertification [and this, somehow, relates to some other unstated assertion].

    You may be saying all of the above, or none, or some. No one knows. You want to dismiss this comment thread as ignoring “inconvenient facts” when in all likelihood your “facts” weren’t compelling due to lack of clarity. Here is an opportunity to clarify them to assuage your concerns.



  44. 194
    Pat Neuman says:

    re 191 … “Can we all agree that if global warming continues as predicted, there WILL be changes to weather patterns?” …

    Weather patterns have already changed.
    See figures and tables at:

  45. 195
    Maurizio says:

    Pat (191): Most of your links are way too generic to be used. And nobody will seriously argue that a change in snow melting in one area can be considered an incontrovertible proof of anything?

  46. 196
    Lloyd Flack says:

    re 192

    Showing that there has been a temperature trend and proving that it is due to human activity are separate problems.

    The reconciliation of the Tropospheric temperature data was the final proof that the temperature is increasing. It says nothing about the cause of the increase.

    The best evidence of a temperature increase is the temperature measurements, not climate pattern changes which are consequences of the temperature increase. True one has to do a lot of work to combine them into meaningful global averages. I’m quite happy with proofs which depend on lots of pieces of data none of which are conclusive by themselves but which it strains credibility to disbelieve in total. Hey, I’m a statistician. It’s what I do.

    If you want the qualitative changes in weather patterns then other commenters on this blog would know better than me what they might be. But they are not proof of temperature trends. The measurements are.

    Where I believe you cannot have inconrovertible proof is in the attribution of temperature trends to human activity. Or rather the attribiution of a major part of the trend. The physics of the situation tells us that increasing greenhouse gases will raise global temperatures. The question is how much.

  47. 197
  48. 198
    Pat Neuman says:

    In 191. Maurizio wrote: “Can we all agree that if global warming continues as predicted, there WILL be changes to weather patterns?” …

    In 194. I replied that … Weather patterns have already changed.
    See figures and tables at: …

    In 195. Maurizio wrote: “Most of your links are way too generic to be used. And nobody will seriously argue that a change in snow melting in one area can be considered an incontrovertible proof of anything”?

    A change in the timing of snowmelt by 4-5 weeks earlier, as shown by a 10 year moving average trend on streamflow runoff, means there has already been “a change in weather patterns”. Winters are warmer recently than decades ago. The polar jet rarely makes an appearance anymore. When the Arctic air does arrive, it’s not as severe or long lasting as years ago (based on 186 years of record at Minneapolis, 100 years of streamflow runoff, and 110 years of temperature measurements at NOAA NWS climate stations in eight Upper Midwest states (sd nd mn wi mi ia il in).

    Links at 194.

  49. 199
    Dano says:

    110 years of temperature measurements at NOAA NWS climate stations in eight Upper Midwest states…

    More ice-free days on the Great Lakes [leading to lower levels due to increased evap.], earlier snowmelt and later ice-up in the NE…



  50. 200