Dealing with climate change deniers

In the last few days I’ve made the mistake of engaging, online, with climate change deniers. It’s incredibly frustrating and I know that I really shouldn’t. Sometimes, though, I just can’t help myself. The problem is that those who deny that climate change is influenced by man are adamant that they’re correct. They make strong, absolute statements: “complete nonsense”, “absolute rubbish”, “the evidence has proven the climate models are wrong”. This is no way to engage in a discussion and makes it impossible to engage in any sensible way.

What makes it difficult is that many seem to have a basic knowledge and understanding of science and use this to back up their statements. They know that CO2 is a weak greenhouse gas and claim this means it can’t be influencing the climate in the way the models indicate. They ignore that, at the moment, CO2 is increasing so fast that it is likely the dominant gas as far as global warming is concerned. They take the surface temperature data for the last 15 years and claim that since there hasn’t been a statistically significant increase, that it proves warming has ended and that the models are wrong. They ignore that 15 years is too short a timescale to make statistically significant measurements and that it could well have risen, we just can’t say that definitively.

The real problem seems to be how they twist the scientific method. The scientific method, in a simple sense, requires that models and/or theory need to be confirmed by observations and/or experiments. If the models don’t match the observations it does mean that there are problems with the models. It doesn’t mean that there is only one alternative. It’s not simply between man-made climate change and non-man-made climate change. It’s clear that humans have released a large amount of CO2 into the atmosphere in the last century. This is a greenhouse gas and must be having an effect on our climate. The question is how big is this effect, not whether it exists or not. The other, related, question is how big can this effect get if we continue as we are.

Another issue is that the typical criticism is that the models predict larger surface temperatures than are currently observed. I suspect that this mis-represents what the models actually do. I suspect that the models actually work with energy, not temperature. We receive a very well known amount of energy from the Sun. Some is reflected (albedo) and some is absorbed. The Earth then re-radiates this energy (at a longer wavelength). This is then transferred through the atmosphere and eventually out into space. The Earth is in equilibrium if the amount of energy received matches the amount that is reflected and radiated back into space. If the Earth receives more than it radiates/reflects it heats up. If it reflects/radiates more than it receives it will cool down.

One way these models could work is to consider the composition of the atmosphere, the Earth’s albedo and then use the incoming radiation to calculate what surface temperature is required for the Earth to be in equilibrium. This, however, is time-independent and doesn’t tell you how long it will take to reach this equilibrium temperature. It also doesn’t tell you how this change in temperature influences atmospheric composition (i.e., it ignores feedback). The alternative (and what I suspect is done) is to consider time-dependent calculations. This, however, is extremely complicated. If we’re not in equilibrium then the excess energy can be used to heat the oceans, heat the surface and atmosphere, and/or melt the polar ice caps. This can take time as the amount of energy required to change the temperature of the oceans or melt the polar ice caps is substantial and differs significantly from that required to heat the atmosphere or the surface. Getting this slightly wrong could significantly change the time evolution of the surface temperature. This could also change weather patterns, like the jet stream or the gulf stream. These changes could also influence how the polar caps melt or how the energy is transferred through the oceans. Running such time-dependent models is extremely difficult and that they don’t exactly match observations is not that surprising.

In a sense what is more important is the energy budget. Are the changes to the composition of our atmosphere requiring that the surface temperature of the Earth rise in order to re-establish equilibrium. There are, in fact, measurements suggesting that currently we aren’t actually in equilibrium and that we receive more energy than we lose. This is shown in the figure below (Murphy et al., 2009, JGR, 114, D17107) which suggests that this has been the case since 1970. If this is correct, then the surface temperature has to rise. There is really no alternative. We just don’t necessarily know how long this will take.

Energy-Flow

Figure taken from Skeptical Science.

This energy imbalance is also consistent with the current situation in which the CO2 levels have been rising without a related rise in surface temperature. If there was no energy imbalance and the CO2 levels had risen without a corresponding surface temperature rise, it would suggest that CO2 was not an important greenhouse gas. That there is an imbalance tells us that the increased CO2 is indeed trapping more energy. This energy must be going somewhere and it appears to be going into heating the oceans and melting the ice caps.

If this energy imbalance is correct, at some point the surface temperature will have to rise. It may be difficult to determine exactly when. It may also be difficult to determine exactly the consequences. Will the melting in the polar regions release methane which is a much more effective greenhouse gas than CO2. Claiming, however, that because the models don’t exactly match observations does not then imply that global warming is not being influenced by man.

This post has got slightly longer than I intended. I was really just wanting to express how frustrating it is to engage with those who claim that our releasing large amounts of CO2 into the atmosphere is not having an impact on the climate. Maybe the models will end up being wrong, but it’s not going to be because climate scientists are making the silly mistakes that climate change deniers claim that they are.

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48 thoughts on “Dealing with climate change deniers

    • Methane is rising though, isn’t it. It’s also a very effective greenhouse gas. Per mass it is something like 25 times as effective as CO2.

      Your latter comment suggests that even if climate change is being driven by man it might not matter. We will equilibrate at some new, higher temperature and maybe we’ll adapt. Maybe, but maybe not. I think this is a very dangerous assumption. There is nothing about the Earth that suggests that it will always equilibrate at a temperature where we can survive (or at least survive as we do today).

  1. Nice post. Yes, frustrating. I often wonder how much ignorance of the science is willful or simply a reflection of poor science education. The energy budget/balance is a good way to look at it. Essentially what Arrhenius started to do way back in 1898 when he first identified CO2 rise as a potential climate changer.

    • Thanks. It’s nice to get at least one positive comment. I’ve never had as many comments in such a short time. I should have guessed that a post like this would generate interest. I may regret that in time.

  2. You sound in this piece like about 90% of the so-called skeptics – your comments and observations (at least in the first half) are congruent with what they say and write.

    • As I mention in another comment, I used the terms deniers specifically. I don’t really have an issue with skeptics. Discussing and debating the science behind climate change and being skeptical is good. Absolutely denying that it is influenced by man is what frustrates me.

      I do think, however, that the skeptics do have to be a little careful. There is an enormous consensus in the scientific community that climate change is being driven by man and we should act to reduce CO2 levels. It’s not absolute: I’ve read that climate scientists are about 90% sure about this.

      I think it’s fine to be skeptical, but I do think it it highly unlikely that some well-educated lay people have noticed an issue with climate science that the climate scientists themselves have been ignoring or haven’t noticed. It’s possible, but very unlikely.

  3. Hi. I’m a first time visitor here. Followed a link from tomnelson.blogspot.com. Every day he puts up links to various relatively new items related to climate. Good site to keep up with what is being said.

    I have no formal science education past high school some 50 years ago, although I have picked up a modicum of knowledge since then. Just consider me one of those people who has learned through experience to apply what knowledge I can muster when someone wishes me to invest in their idea.

    When you say climate change deniers I suspect you don’t really think some significant portion of humanity thinks climate never changes. What I suspect you mean is they don’t consider co2 the main driving force behind temperature change and you do. It is rather poor form to call them deniers, but using that definition I must consider myself a denier.

    You complain people use the fact that there hasn’t been any statistically significant change in temperature in 15 years and view it as meaning nothing because 15 years is too short a time to achieve statistical significance. What you fail to understand is it isn’t the length of time which determines the significance it is the magnitude of change over time. As such they are quite right in saying the temperature change is so small that it cannot be differentiated from no change at all. It is statistically insignificant. If the temperature rose 0.1C per year for even just 10 years, you would be shouting and worrying about it and you would have a reason to do so because it would be a statistically significant change even though the time period is shorter than the 15 years you currently wish to ignore.

    Given that there hasn’t been any significant temperature change in the last 15 years, I am starting to feel rather confident that co2 is only a minor player in temperature rise and that many of the spokes-persons have been over-egging the pudding so to speak. Frankly, I’m not willing to spend any portion of my children’s or grand-children’s inheritance on some co2 mitigation scheme that hasn’t been shown to be either necessary or effective. A warmer world extends both crop growing range and season length and more co2 both improves the growth of most crops and enables many of them to be more drought hardy.

    PS.
    It would have been nice to know the source URL of your graph above. The highest point in that graph seems to be in the mid-1950s when co2 was about 315 ppm. Since then co2 has risen 25% yet the 1950s value hasn’t been exceeded. Also, that jump in the mid-1970s coincides with the PDO shifting from its cool phase to its warm phase. I fail to see how that graph helps any argument concerning the effect of co2.

    According to this graph, whatever worry one wishes to invest might better be directed toward worrying about cooling rather than warming.

    Have a healthy and happy new year.

    • I did wonder about using the term deniers, rather than skeptic. I do mean deniers. I mean those who absolutely deny that climate change is being influenced by man. I was being slightly provocative in using it, but I was trying to distinguish between absolute deniers and skeptics (who may well engage in a sensible scientific debate). I should probably have made that clearer but it did become a slightly longer post than I had intended.

      As far as the 15 year time period is concerned, the change is something like 0.084 +- 0.15 degrees per decade. The trend is therefore positive and is indeed almost 0.1 degrees per decade. It’s not statistically significant because the 1 sigma error suggests that there is a chance that it could be negative. However, interpreting this probably depends on where the error comes from. If it is natural variations and the measurements are accurate, then the trend probably correctly reflects the warming. If the error is a measurement error, then we don’t know if the correct trend is bigger or smaller than the mean.

      The figure is from Skeptical science. I wouldn’t take the 1950s data that seriously given that it has large error bars and was presumably the beginning of the data set. It’s an 8-year running average, so you need about 8-years of data before you can really start trusting the values (or at least before the values become consistent with each other).

      I don’t really understand your last comment and the relevance of the link

      Happy New Year to you too.

  4. You state: “It’s clear that humans have released a large amount of CO2 into the atmosphere in the last century.”
    Excuse me…4% of atmospheric CO2 is attributable to anthropogenic sources. As CO2 comprises 0.038% of the Earth’s atmosphere I hardly think this amounts to “a large amount.” This absurd statement reveals your inherent, unscientific political bias.
    You’d be better off discussing climate sensitivity to this amount of CO2 and the established fact that temperature leads (not lags) atmospheric concentration of CO2. The fact that global temperatures have shown no significant rise in the last 16 years, in the face of rising [CO2] flies irretrievably in the face of ALL IPCC model projections and invalidates the hypothesis of catastrophic anthropogenic forcing. There is of course a theoretical rise in temperature associated with increasing [CO2]. Of the 0.7C seen in the last century, I understand 0.5C occurred before 1940, when anthropogenic sources are associated with rise. The models also fail to account for the glaring fact that the Antarctic Ice has expanded to an all time record (at least since records began).
    The fiddling of temperature data by adjustment, sometimes undisclosed, renders such small global temperatures changes impossible to take seriously, particularly when it is established that previous warm periods have occurred without so called anthropogenic forcing – Roman, Mayan, Medieval Warm periods. The absurd cost of deluding ourselves that we can actually influence the temperature is the most recent manifestation of a particularly toxic version of political arrogance.
    And then there is a certain loss of credibility associated with UEA Climategate emails, the ridiculous and debunked Hockey Schtick, difficulty in obtaining data and understanding ‘adjustments’ from researchers.
    Face it. The meme is full of holes. Climate science is definitely not ‘settled’. The associated political agendas grow daily ever more obvious.

    • You’re partly illustrating my point. Your comment isn’t really open for debate. You’re very certain and use terms like “ridiculous”, “debunked” and “toxic version of political arrogance”. I can find plenty of discussion that argues that the Hockey Stick graph has not been debunked. If fact, I have looked at the literature and it has been replicated using numerous different methods.

      I’m also confused by your claim that 4% of atmospheric CO2 is attributable to anthropogenic sources. For the last 500000 years the atmospheric CO2 level has not exceeded 290 ppm. Today it is 380 ppm with about 50ppm being added in the last 50 years. My understanding is that this is all regarded as from anthropogenic sources. This would indicate that something like 30% is from anthropogenic sources. Also, where does the temperature leading the CO2 statement come from. From the data I’ve looked at the CO2 levels started increasing just before 1800 and the temperature started rising just before 1900. That seems the opposite to what you suggest.

      In a sense my post was more about the manner in which we undertake this discussion than the discussion itself. I clearly think that the climate is being influenced by man and that we should act to reduce CO2 levels. This is based on reading about the subject, looking at data, and through my own involvement in a complicated science area that makes me realise that simple analyses are often not good enough to understand what is happening. I’m happy to be convinced otherwise, but that’s not going to happen simply because someone tells me I’m wrong.

      • I disagree. My comment is entirely open to debate as you have illustrated with your kind response. Nevertheless, your use of the word ‘large’ does illustrate a qualitative bias.
        No doubt you’ve seen the recent IPCC draft AR5 Figure 1.4 of the temperature anomaly 1990 – 2015. Nice graph isn’t it? It shows modeled projections against empirical observations and not only the uncoupled relationship between models and reality, but between escalating temperature and proportional increases in CO2 – a truly miniscule proportion of atmospheric composition – at around 0.03%.

        http://wattsupwiththat.com/2012/12/14/the-real-ipcc-ar5-draft-bombshell-plus-a-poll/

        Do please check the Vostock/CO2 data for yourself to ascertain the lead/lag argument – widely published on the net.

        I understand that it will soon be possible to empirically establish climate sensitivity, the suggestion being that it is anticipated to reside well below inflated IPCC estimates, thus relieving you of the burden of trying to prove the CAGW hypothesis. In the meantime, the climate / weather preoccupation has conveniently expanded into anthropogenic influenced climate / weather change. As for the first term, it is a non-specific all encompassing qualitative statement better suited to politics than to science. The second term is axiomatic – global temperatures and sea levels have wandered all over the axis over the last hundreds of millions of years. Presently, both are far below previously seen elevated levels – the obvious adage – the more it changes, the more it remains the same – springs to mind.

        I’m interested. You state: “I clearly think that the climate is being influenced by man and that we should act to reduce CO2 levels.”
        I’d be really pleased to learn of that seminal moment you had, the pivotal, the key empirical article that you discovered, which demonstrated the relationship to your satisfaction? Then the subsequent key research that you found, which convinced you by how much CO2 levels should be reduced, and how this should be achieved, the considered time frame to arbitrarily ‘fix’ global temperatures – by how much? for how long? and to decide what is ‘normal’.

        In any event, half a million years of stable CO2 levels is but the briefest of time in the geological record. The argument that the last sixteen years is insufficient time to reveal a true trend in temperature is no less valid for your half a million years of stable CO2 levels, when one looks at CO2 levels over hundreds of millions of years, and yet you accept changing CO2 levels in the short term as meaningful in the face of unrelated temperature change (flat line in the last sixteen against rising CO2 levels), and up and down in the last century, against rising CO2 levels. I don’t dispute a theoretical rise in temp attributable to anthropogenic causes, but it is minute, irrelevant and inconsequential in my view and in that of millions of others, including thousands of bona fide scientists – as indeed I’m quite sure you know.

        As I stated previously, the climate science is definitely not ‘settled’. And because of this, the associated political agendas grow daily ever more obvious and ‘toxic’ – depending upon one’s perspective, naturally.

      • Manfred, I can’t tell from the beginning of your comment if you’re being ironic or not :-)

        The Figure you refer to in the IPCC draft does indeed seem to show that the estimated surface temperature from the models is higher than what is currently being measured. What I was trying to indicate in my post was that the real issue is whether or not there is an energy imbalance. There appears to be one and this could explain this difference. If there was no energy imbalance and the rising CO2 was not associated with a rising surface temperature, then this criticism of AGW would have more merit. It may be that the models are underestimating the timescale, but it’s not yet clear that they’re underestimating the magnitude.

        As far as the temperature leading the CO2, I assume you’re referring to the long-timescale data that is obtained from ice core samples. As far as I’m aware this is not relevant. As I mention in another comment, these are driven by Milankovitch cycles (variations in the Earth’s orbit, axis tilt and axis precession). This changes how much energy is deposited on the Earth and where it is deposited. This heats the oceans and melts the ice caps releasing CO2 which then amplifies the warming (as the orbital variation itself is far too small to explain the measured variations). It would be surprising if the temperature did not lead the rise in CO2 as the reverse would imply that rising CO2 in our atmosphere somehow influenced our orbit.

        As far as my comment about CO2 is concerned, I used the words “clearly think” on purpose. I was making my opinion clear. It is based on my readings around the subject, my understanding of science and a sense that continually increasing CO2 levels is unlikely to be a good thing to do. As I’ve mentioned elsewhere, it’s unclear to me why it wouldn’t be a good thing to start investing in developing new technologies for providing energy. We’ll almost certainly need them at some stage in the future and being ahead of the game will almost certainly be good for our economy (compared to those who choose to ignore this).

        As far as whether or not the science is settled, that may be strictly correct. There is, however, a very strong consensus amongst active climate scientists. They are, largely, publicly funded and are obliged, in my view, to indicate if their research suggests that we may be heading for a problem if we don’t address (for example) CO2 levels in the atmosphere. We (our governments) can choose to ignore this, but we shouldn’t claim that such a consensus does not exist (although I’m not suggesting that you’re making such a claim). We also shouldn’t – again in my view – claim that simply because it isn’t absolutely settled that we don’t need to be concerned about the implications of AGW.

  5. “They ignore that 15 years is too short a timescale to make statistically significant measurements…”

    Be careful here. Santer et al have a recent study in JGR where they conclude: “Our results show that temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature.” http://www.agu.org/pubs/crossref/2011/2011JD016263.shtml

    As well, NOAA in a recent climate statement noted the following about temperature observations vs climate models: ““Near-zero and even negative trends are common for intervals of a decade or less in the simulations, due to the model’s internal climate variability. The simulations rule out (at the 95% level) zero trends for intervals of 15 yr or more, suggesting that an observed absence of warming of this duration is needed to create a discrepancy with the expected present-day warming rate.”

    And Phil Jones stated in a Climategate email: “‘Bottom line: the ‘no upward trend’ has to continue for a total of 15 years before we get worried.’”

    To say 15 years is too short a time scale is a subjective statement. It’s not like math where there’s a proof. And it looks like 2012 will be something like the 9th warmest so the recent lack of warming is continuing.

    What is you own personal opinion where a lack of warming vs climate model predictions would be significant?

    • Thanks for the comment although I am a little confused. It seems marginally consistent with what I was saying, although maybe my statement was a little stronger than what you’re saying here. It does seem like 15 years is right on the boundary of being able to make statistically significant statements.

      What I don’t know (and would be interested to know) is the source of the error in the 15 years measurements to which people seem to be referring. The value I have heard is 0.084 +- 0.152 degrees per decade. If these measurements are accurate and the error indicates natural variations in the global surface temperature, then the trend presumably is a real reflection of the warming and indicates that, on average, the surface temperature (over the last 15 years) is increasing at about 0.1 degree per decade. If the errors are measurements errors, then the warming could be negative or it could be as high as 0.3 degrees per decade and we’d need more data to make get a better sense of the trend. It presumably is some combination of the two.

      It seems, to me at least, that the required timescale then depends on which of the above is dominant. If the natural variations are comparable to the temperature change per decade, then presumably you would need at least two decades to extract a statistically significant signal from the noise. If the dominant error is measurement error, maybe you need even longer. Or maybe I’ve misunderstood this. It does seem, however, that claiming that man-made climate change is now debunked because of a discrepancy between the models and the measurements over the last 15 years is not a statement that can yet be made.

      • Claiming that AGW is debunked based on our conversation is in my mind an unsupported conclusion. 15 years can certainly be due to natural decadal variation (forgetting about measurement error for a moment).

        Having said that, I would be much less skeptical if the warming which started in 70s had continued and even increased. However, regardless of significance, the fact that the trend from say 1980-1995 was strongly positive but has since tapered off certainly indicates something else is at play when looking at the increase in CO2 over the entire period.

        I’m loath the come to any definite conclusion about what is going on. I’ve read that Chinese aerosols from increased coal burning may have a global cooling effect. That’s pretty speculative. In the end, the possibility that climate sensitivity of a best guess of 3C has been overestimated is still in play. That’s really what the skeptic discussion about the recent pause in warming is about.

      • MikeC, I agree that 3 degrees this century may be an overestimate. We can’t say for certain. That man is influencing the climate seems less questionable. What always confuses me is why so many object to the suggestion that we should be reducing the amount of CO2 we’re pumping into the atmosphere. I can’t see any reason why ever increasing levels of CO2 would be a good thing.

        If we can find alternative ways to provide energy, why is that such a bad thing? In the process of developing this technology, all sorts of other unexpected benefits will probably be found. It seems to me that being ahead of the game would be a real positive and that we should be investing in this type of research now so as not to be left behind. Presumably we’ll need it at some point anyway.

  6. So, how does “the scientific method” square with the fact that CO2 lags temperature in the climate record ? It’s rather difficult to claim that fluctuations in CO2 caused shifts in temperatures when the shifts in temperatures predate the fluctuations in CO2.

    • Maybe you can provide a link or some evidence for this. This has been claimed by another commentor, but is not consistent with what I’ve seen in the data. From what I’ve seen, the rise in CO2 started just before 1800 and the increase in temperature started just before 1900.

      If, however, you are correct the the rise in temperature started before the rise in CO2 then I would agree that that would be a problem that would need explaining.

    • Yes, but that’s due to Milankovitch cycles. Variations in the Earth’s orbit and in the inclination and precession of the axis changes the energy that the Earth receives and where it receives this energy. It melts the glaciers and heats the oceans. This releases CO2 which results in feedback and produces variations in temperature of about 10 degrees and CO2 levels that vary from about 180 ppm to about 280 ppm. The cycles last about 100000 years. The initial driver is the Milankovitch cycles with the CO2 amplifying the variations and so it’s not surprising that the CO2 lags the temperature. If it was the other way around it would suggest that somehow releasing CO2 produces variations in the Earth’s orbit, which doesn’t really make sense.

      We’re currently near the peak of a Milankovitch cycle and so would expect CO2 levels of about 280 ppm. Since about 1800 the CO2 levels have increased to about 380 ppm, about 100 ppm more than it has been for the last 500000 years. It is this sudden increase that is worrying and it has preceded any additional warming. There is no evidence that some natural increase in surface temperature has driven the CO2 levels to this historical (at least in the last 500000 years) high.

  7. Plant stomata confirms the lag and also tells us that atmospheric concentrations of CO2 are variable and not nearly as stable as suggested.

    “Mcelwain et al., 2002 found that a “~77 ppm decrease in atmospheric CO2 at the onset of the Younger Dryas stadial… lagged climatic cooling by ~130 yr.” The stomata data clearly support a temperature-driven carbon cycle.”

    “Once dissolved in the deep-ocean, the residence time for carbon atoms can be more than 500 years. So, a 150- to 250-year lag time between the ~1,500-year climate cycle and oceanic CO2 degassing should come as little surprise.”

    http://debunkhouse.wordpress.com/2010/12/25/co2-ice-cores-vs-plant-stomata-wuwt/

    • I’m not disputing the lag. I’m disputing the relevance. The orbital variations (Milankovitch cycles) are unable to produce, by themselves, the measured temperature variations. It’s requires additional forcing from CO2. These cycles therefore show that CO2 can act to produce reasonable amounts of warming, but the temperature presumably has to rise before the CO2 in order for the cycle to start.

      Your link seems to be a link suggesting that the ice core CO2 measurements underestimate the long-term CO2 levels. I don’t know enough about this to comment other than to point you to the following link which suggests that plant stomata are not necessarily a reliable estimator for historical CO2 levels.

      http://www.skepticalscience.com/plant-stomata-co2-levels.htm

  8. Milankovitch cycles are long term and don’t explain the Halocene Maximum, the Roman Optimum nor the Medieval Warming Period.

    • Certainly, but maybe you can elaborate on the relevance of these. There is debate about the overall significance of these warm periods and that they may be simply consistent with natural variations. The problem is that, today, the CO2 levels are not consistent with natural variations and the subsequent warming may be a major problem.

      • Well those warm periods are obviously natural variation. And it is agreed that CO2 levels are very likely higher now than would be naturally due to man’s CO2 emissions.

        However, one of the arguments for CO2 being a significant forcing is that the current warming is not consistent with natural variation. This is augmented by claims that the warming is unprecedented. If it wasn’t, then natural variation could explain all of it.

        This is another strong skeptic argument in that today’s warming has not been proven to be unprecedented. If you think the error margins of current, modern temperature measurement devices are large, think of how hard it is trying to determine an average annual global temperature 500, 1000 or 10,000 years ago. The skepticism is against the confidence in such reconstructions and the subjective (and unfortunately sometimes secretive) manner in how decisions are made in these studies (e.g. the “hockey stick”).

        Using the MWP as an example, there are hundreds of individuals studies from around the globe which support a very warm period. Here is a very good compilation all leading to peer reviewed scientific literature: http://www.co2science.org/data/timemap/mwpmap.html

      • MikeC, I guess it’s not quite clear to me why finding another epoch in the last few thousand years that was as warm as it is today would necessarily be a smoking gun against man-made climate change. There are clearly natural effects that can produce reasonably large variations. Also, as far as I’m aware, the issue today is more the trend than the magnitude. Obviously, if the upward trend continues we would expect it to reach some kind of level that was unprecedented, but I didn’t think any climate scientists were claiming that we were definitively there yet.

      • I never said it was a smoking gun to overturn AGW. However, if we cannot conclude that recent warming is unprecedented, that would take away one of the pillars of support. And believe it or not, that pillar is leaned on quite heavily.

        Although, if you have noticed it is not so much the recent temperature trend that is discussed, it is now all about extreme weather. And again, the theme is unprecedented or a new term which appears snatched out of mid-air: the “new normal”.

        I predict that unless global average temperatures go up again or we hit a new annual record, the focus will be on every weather event which goes sour for man. To me, that’s the “new normal” (for the PR end anyways).

        I like to stick to the science and I feel I’m being lured to the political so I’ll sign off for now.

      • Apologies if you thought I was implying that you were indicating that they would be smoking guns. It was just a general comment about whether or not even some earlier epochs being warmer would be that significant in terms of disproving AGW.

        I tend to agree with you about the extreme weather events. There was a period not very long ago when if anyone said “climate change must be wrong because we’ve had an incredibly cold winter” the response would be “climate and weather are different”. That we’re now suggesting that these extreme weather events are related to AGW is a little worrying in that we clearly cannot make that claim. It could be consistent, but I can’t believe that it’s yet proven.

        I also agree that if we don’t see increases in surface temperature sometime in the near future, it will make it difficult to continue to claim that AGW is real. I can’t claim to know when that should be, but if we see flat or decreasing temperatures for the next 10 years, that would be difficult to explain. I’d be surprised if we don’t see the rise continuing but, at the end of the day, we should rely on the science and not our opinions.

        Thanks, anyway, for the comments. I’ve found them very instructive.

      • Just one last note. I have been called a “denier” many times. So please consider our exchange as some sort of empirical evidence seeing as the title of your post is “Dealing with climate change deniers”.

        I’m not saying there aren’t nutbars who think AGW is some sort of New World Order to implement socialism. But most people who question the more severe effects and are thus skeptical of AGW are like me. I agree that CO2 is a greenhouse gas, that it has been warming for at least the past 150 years, that man has contributed to warming and that it may be a problem.

        When I ask those who call me a denier what I am denying I can’t get a straight answer. I just look at the science and try to figure out when something is being distorted. And I’m fully aware that it happens on both sides. It’s just that simple.

        By the way, as an ironic note, my political leaning is left of center.

  9. Is it any wonder you got frustrated? You spent days “dealing with” imaginary people. “Climate change deniers” don’t exist. Everyone you wasted time evangelising was well aware that the climate changes.

    If you systematically mislabel and infantilise people, do you seriously expect them to then give your opinions a sympathetic hearing?

    • Thanks for the comment. Reasonably unpleasant, so kind of what I was getting at in my post. Also, can’t quite tell if you’re trivialising man-made climate change or not. As I mentioned in an earlier comment, I really was referring to people who do totally deny that climate change is being driven by man and who clearly exist (despite what you may or may not think). I also made that fairly clear in the post itself. I have no issue with those who are skeptical and engage in a sensible, balanced and pleasant manner.

      • “Thanks for the comment. Reasonably”

        You’re welcome! Always interact reasonably, is my philosophy!

        Upthread, you seem to be in a sustained and amicable dialogue with an AGW skeptic. Presumably you consider it an improvement over the ones you were having previously? What do you think made the difference? I’ve noticed that location matters a lot. There are some climate sites where people seem to be looking for a fight (and won’t change their minds no matter what). I think we’ve all wasted a couple of days in a quagmire like that. You know you’re not going to achieve anything—but it’s morbidly irresistible anyway.

        You still seem a bit confused as to what to call my “side.”

        The problem with “climate change deniers” is that it’s simply false. The falsehood is not in the verb “deny”, which is simply an antonym of “accept” (though it has a tone that’s pretty much guaranteed to antagonise a lot of your readers). The error lies in what you’re claiming we deny. We do not deny climate change! We don’t even doubt it.

        What we deny (or doubt) is (catastrophic) anthropogenic climate change. (Some of us think the manmade temperature signal is undetectably weak; others accept that it’s significant, but see nothing alarming about it.)

        May I suggest, therefore, that you try “[C]AGW skeptics.”

        Admittedly that has the side-effect of implying that people who don’t believe in [C]AGW are critical thinkers—which isn’t always the case!—and that people who do accept it are credulous or unscientific—which isn’t the case either.

        So a good alternative would be “[C]AGW doubters” or “disbelievers” or “infidels” or “rejectors.”

        Take care,

        Brad

        PS There’s one trap that a lot of believers seem to be falling into (though I don’t think you’ve done this), without even realising quite how nasty they sound: please don’t ever accuse an intelligent, decent adult of denying *science.* That’s the end of the conversation right there. Put yourself in their place for a minute. “Climate science denier” is a pretty way of saying nigger. Hardly the way to build bridges. If we can somehow lift the bitterly adversarial spell that’s fallen on the whole climate change question, I think you’ll be pleasantly surprised by how much common ground we all have. We deniers are people too.

      • I think you’re making the mistake of assuming that I was aiming this at someone who may be like yourself. I really was meaning “deniers”. I know that I could have used “skeptics” or “doubters”, but I didn’t want to. I mean those who I’ve encountered online who won’t accept any of the evidence that is presented to them. Those who seem to think there is some kind of left-wing conspiracy. Those who think that climate scientists are intentionally fixing their data or their models so as to get results that support AGW. If this isn’t you, then this wasn’t aimed at you. I suspect my post didn’t make this as clear as maybe it could have, but that was the intention.

        As you yourself acknowledge, I seem capable of having a pleasant exchange with those who are skeptical. I think being skeptical is a good thing. I do, however, think that skeptics do have to be slightly careful. There is a very strong consensus in the climate science community that AGW is real (let’s say they are 90% sure). They could be wrong, but it is unlikely that they’re missing or ignoring something that an educated lay-person has noticed and has assumed is somehow significant.

      • Hmmm. It sounds really exasperating—and I’ve encountered things like that myself, only from the other “side”. I’d be very interested to see this from your point of view though—I think empathy is the only way forward at this point—so can you tell me the URLs where this took place?

  10. Pingback: So, that’s how you increase readership! | To the left of centre

  11. Satellite measurements confirm that CO2 is not evenly distributed and that values over the poles are less than those found at other locations in the world. Funny how plant stomata shows the CO2 lag from the Medieval Warming Period yet ice cores don’t. We know that this warming period occurred because of our history is full of examples of the period, ie. the Vikings, so why don’t the ice cores show it unless they have a problem with resolution ?

    ” The problem is that, today, the CO2 levels are not consistent with natural variations and the subsequent warming may be a major problem.”

    This is where the scientific method comes into play. The climate record is conspicuously devoid of CO2 induced climate change, warming or cooling. It can’t be found and instead we always seem to find the ever repeating CO2 lag pattern. So, with the scientific method in mind, why should it be believed that shifts in CO2 induce temperature change ? If anything it’s reasonable to come away from this believing that CO2 is function of temperature and not the other way around.

    • I don’t understand your last paragraph. The Milankovitch cycles show temperatures variations of 10 degrees and CO2 variations of between 180 ppm and 280 ppm. The orbital variations associated with the Milankovitch cycles are insufficient to explain these temperature variations and so the general interpretation is that, at the start of a cycle, the change in energy deposition releases CO2 which then acts as a greenhouse gas and amplifies the warming, releasing more CO2 etc. My understanding was that these cycles were strong evidence for CO2 induced warming.

  12. The study’s conclusion:

    “There exist a clear phase relationship between changes of atmospheric CO2 and the different global temperature records, whether representing sea surface temperature, surface air temperature, or lower troposphere temperature, with changes in the amount of atmospheric CO2 always lagging behind corresponding changes in temperature.”

    The full report may be accessed at the Global and Planetary Change Volume 100, January 2013

    • Interesting, thanks. I haven’t read it in detail but from I can see one should be a little careful in how one interprets this. It seems to be looking at the small variations in CO2 levels that appear on top of a long-term rising trend (Figure 1 for example). It appears to be showing that the small variations are driven by variations in surface temperature. It’s not clear, however, that it can make any claims about the long-term trend of increasing CO2 levels. I shall aim to read it more carefully and will be interested to see other papers that refer back to this.

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