What do we know about climate change?


This excellent video gives a nice overview of what we know about climate change:

It’s part of Peter Sinclair’s (a.k.a. Greenman3610) “climate crocks” series.

(Script, graphs and links to some of the relevant papers here)

My short version:

– Globe is warming

– It’s due to us

– It’s bad news

– Uncertainty + Inertia = Danger

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78 Responses to “What do we know about climate change?”

  1. RickA Says:


    It seems that based on the last three interglacials, that the peak Antarctic interglacial temperature was at least 6 degrees C above the present day temperature.

    I am basing this off this letter to Nature:

    Nature 462, 342-345 (19 November 2009) | doi:10.1038/nature08564; Received 9 October 2008; Accepted 5 October 2009
    Evidence for warmer interglacials in East Antarctic ice cores – which indicates: “that the available evidence is consistent with a peak Antarctic interglacial temperature that was at least 6 K higher than that of the present day — approximately double the widely quoted 3 +- 1.5 K.”

    We are currently in an interglacial.

    What if it is normal to warm up to 6 degrees C above our present temperature during an interglacial?

    Might we be fighting a losing battle to slow down the temperature increase?

    If that was the case – what a waste of money.

    Why should this interglacial be different than the last 3?

    What are your thoughts on this?

  2. dhogaza Says:

    They’re speaking of three particularly warm interglacials, the most reacent, the Eemian, being about 125,000 years ago.

    As a result, sea levels were 4 to 6 meters higher then than now.

    There are more people living in places like Miami and Bangladesh (to mention two) now than 125,000 years ago, that’s the difference.

    Remember, the concern here is on the impact of warming, due to both indirect and direct effects, on humans.

  3. Bart Says:


    They refer to Antarctic temps; global is lower. Numbers I’ve seen for global avg temp during the last interglacial is 1-2 degrees higher than now (but also polar amplification). Plus, as dhogaza said, sea levels were 6 m higher than today. Not very comforting, with such a relatively small temp increase.

  4. Tom Fuller Says:

    If there are forcings that have operated during previous interglacials that brought temperatures up so dramatically, how would they be countered? (I’m obviously not including CO2 or other known factors, such as Milankovitch cycles, etc.)
    [Reply: Why are you obviously not including those? I’d think that the answer to your question is precisely in them: The Milankovitch forcing gradually reverses into causing gradual cooling, which is amplified by feedbacks, notably from CO2 and ice sheets. BV]

  5. SiP Says:

    Uncertainty seems to be the new buzz word. The science is uncertain but we must presume certainty/calamity and act accordingly. Have I summarised you correctly?

    I watched Chris Fields debate with Roger Piekle Jr on Newsnight on the BBC. Fields was evasive and defensive when he needn’t have been. As Pielke pointed out the science in question (no increase in hurricanes with global warming) was clear and undisputed by everyone so why did Chris Fields not simply agree?

    That week there was a ‘debate’ (more discussion as they all agreed) at the Royal Institution with Roger Pielke Jr, Bob Ward and Robert Muir-Wood on the same subject and all concurred: no increase in hurricanes with global warming, the wrong graph used in the IPCC report.

    Zero uncertainty.

    I know this is only one issue. I know it does not ‘disprove’ anything else but if you lump all the climate science together as you have implied here you will just get quizzical comments from trolls like myself.

    Some of the science is certain, some is uncertain: the physics is certain, but the knowledge of how the climate system works, feedbacks, etc is less certain. We thought past temperature data was certain but now it looks uncertain. UHI is also uncertain. Climate models are very uncertain. Some of the statistics also looks a little uncertain tho’ this blog has produced the best discussion on the subject – that is for certain.

    Decarbonisation is certainly a good thing tho’ the economics of how and especially when are less certain.

    More definition and honesty of what is uncertain and what is not would help greatly. But to try and wash the whole subject with ‘uncertainty’ and then pretend it passes a credibility test will not do.

    [Reply: No, you have summarized my position entirely wrong. “Risk” is the new buzz word (or it ought to be). Uncertainty (in the face of a credible threat) leads to a greater risk. In a snowstorm it is advisable to reduce speed. Unless you’re very confident that the threat is very small.
    You seem to declare “certainty” when you like the result, and declare “uncertainty” (wrongly taken to mean knowing nothing at all) when you dislike the result. Have I summarized you correctly? BV

  6. SiP Says:

    Thanks, for your correction, and you have summarised my position as incorrectly as I did yours ;-)

    I am basically puzzled rather than assertive so if I got the uncertain parts of the science wrong then I apologise, do put me right.

    Your video,from what I understood, said global warming has produced more bad weather events/precipitation/disasters and my understanding (from a real scientist) was that this was not true that disasters etc had not increased.

    In your preferred terminology the risk of disasters is low. I am not cherry picking here – this seems to be ‘settled science’ from what I can tell. So snowstorm, rain or hail, it wont be due to global warming it will be just the weather.

    So again can you define the risks and be honest about what the actual problems are? (Btw I was not at all convinced by the video – seemed like they were trying to sell life insurance -sorry)


  7. SiP Says:

    The mystery graph


  8. sailrick Says:

    ” As Pielke pointed out the science in question (no increase in hurricanes with global warming) was clear and undisputed by everyone so why did Chris Fields not simply agree?”

    All that statement does is confirm that deniers distort the science and the words of the IPCC scientitsts. Maybe you are not doing this intentionally, but your source certainly did.
    The IPCC doesn’t claim there will be more hurricanes, but that more of them will be intense.

  9. ScP Says:

    Bart you should read The Hockey stick Illusion by Andrew Montford – reviewed here – a very enjoyable read.


    Sailrick -I think the point that Pielke was making is that the IPCC got it wrong – do look at the posts linked above and let me know what you think he is saying.

    Here is the clip from the interview with Chris Fields on Newsnight – it is quite short.


    [Reply: Thanks, but I’d rather get my scientific info from scientific articles and books. Perhaps you should too. This book is both an enjoyable read and stays close to the scientific facts. No speculation or conspirational thinking. BV]

  10. ScP Says:

    I will let Roger know you dont think he is a scientist ;-)

    Andrew is a chemist and science editor so should be scientific enough for you – it is not a polemic or op-ed.

    I dont think you can get a much better place than the Royal Institution for promoting science and at the discussion I referenced there no dispute among the speakers about AGW.

    I asked a question above about risk – is there an answer?

    I am checking the Spencer Weart site in case you have hidden your answer there!

    I agree no speculation, no conspiracy, just science (and no insults)

    [Reply: My comment was directed at the illusion book. You can find my take on Roger’s position here. BV]

  11. ScP Says:

    Bart, re Risks of climate change.

    I am guessing this would be your answer – the list towards the bottom of the page


    Yes? Can you now comment on Pielke’s position?

  12. Marco Says:

    @ScP: knowing Montford’s writings and his polemic ‘evidence’ provided to the public inquiry in the UK, his many FoI requests in the UK (and not just to UEA), I’m afraid *I* will not trust Montford’s book NOT to be filled with polemic. I hope Bart is wise enough not to spend money on the book you recommend.

  13. Paul_K Says:

    Hi Bart,

    The video is a very slick puff-piece, but leaves me unimpressed, as does any propaganda piece which uses the term “Denier” to denigrate any challenge, including reasoned scientific challenge.

    Breaking down the time elements in the movie:
    On the question of estimation of climate sensitivity, probably the primary issue for serious skeptics: Zero time
    On the question of attribution, another critical question: 42 secs of mostly unsupported assertion.
    On the question of whether there is evidence that the globe has been warming in recent decades: nearly all of the rest of the time.

    The only (briefly imaged) empirical evidence of attribution (I’m sorry I really can’t take a picture of a tuned GCM model match very seriously)was the Harries et al series of papers between 2001 and 2003. In my view, they do provide direct empirical evidence that increased CO2 leads to a net reduction in OLR within the main emission bands of CO2. Incidentally, if my recollection is correct, the same Harries data also show an increase in total OLR over the same selected time interval; this is compatible with the downloadable averaged OLR data available from the NASA site, and is less easily explained by AGW, but I see a moderator’s flag raised as I head OT….

    My overall feeling about the video is “Thank you for that message from our sponsors. And now we return to considering the scientific basis for how much, if any, of the warming over the last 150 years can sensibly be attributed to CO2 increase?”

  14. ScP Says:

    Hi Marco
    have you got a link to the Montford ‘polemic evidence” . I watched the whole of the UK gov select committee hearing so I would be interested to compare/contrast.

  15. Marco Says:


  16. ScP Says:

    Thanks Marco – am scanning for the ‘polemics’ and have not found it. Reads more like the Institute of Physics submission.


  17. Al Tekhasski Says:

    I agree with Paul_K. I think you summary is overblown and is more of a wish. This piece is a classic AGW propaganda.

    Yes, all signs of warming are consistent … with warming. What a surprise! However, the link with greenhouse effect is unsubstantiated. The reference to laboratory experiments and prehistoric calculations are irrelevant.

    Processing of satellite data by Harries et al is not convincing either. First, the 1970 instrument had inadequate resolution and excessive noise exactly in the area of interest. Second, they have to discard 99.3 % of spectra to get their baseline for 1970. This selection of 1 out of 100 does not sound convincing. Third, they have to subtract “water vapor” and “correct for temperatures”, which is another dubious and subjective operation. As result, it may be true that the OLR spectrum has some rearrangements, and emissions are slightly less from CO2 absorption bands. However, some areas seem to be more intense, and the illustration of deformation in initially normalized spectrum is misleading. So, the inference from the movie that overall “less energy is coming out” is not supported (as Paul_K pointed out).

    Other “supporting” works are of the same dubious scientific quality, but you probably do not want do discuss it.

  18. Scott Mandia Says:


    Why do you think hundreds of experts are all wrong?

    If you are going to be the next Galileo, you will need to do more than point your finger.

  19. Al Tekhasski Says:

    Let please not to generalize too much. I was talking not about hundreds, but about these few particular experts in interpretation on satellite data. If you have to say something in the defense of this particular work, say it, with substance please.

    To be concrete, do you think that using only 25 out of 3662 spectra is scientifically sufficient to establish the 1970 baseline?

    Click to access paper_4.pdf

    To clarify the question, the cloud cover is assumed at about 60%, so one would expect about 1400 qulified spectra. The come down to 25 for 1970. Why? To caompare, the other data have about 32% and 14% of [allegedly] cloud-free data.

    Could you provide an error bar for 1970 spectral baseline?

    Why the difference between 1997 and 2003 data is bigger than between 1970 and newest data?

    Now, the claim in movie is that decrease in OLR is proven by this work. However, the work is about clear-sky conditions only. What about all-sky OLR?

    Do you agree that the claim of reduction in OLR due to increase in GH gases is short of being supported by this satellite “re-analysis”?

  20. Jack Hughes Says:

    // “In a snowstorm it is advisable to reduce speed. ”

    Let’s look more closely at this analogy. The world has been driving in the snowstorm for the last 100 years with no problems. Why reduce speed now just because someone shouts “wolf ahead” ?

    [Reply: Good question. It’s because it’s a slow motion storm. Ok, the analogy breaks down a bit here. For that part, it’s more like smoking. The effects are cumulative: If you stop smoking when you’re driven to the IC, it’s (too) late. Because of the slowly compounding effects, you have to stop smoking early (long before hitting the IC) to reduce the risk. Plus, there is a lot of intertia in all the parts of the problem-solution, so time works against us on multiple levels. I’m planning a post on that. BV]

  21. Scott Mandia Says:


    I am certainly not an expert on interpreting satellite spectra nor in the required corrections to ferret out the CO2 signal. Having said that, why should I assume that these folks are wrong and you are correct? I cannot find any published work by you on the subject. Do you have any?

    I tend to trust peer-reviewed articles, especially when those articles are referenced by other articles, than unpublished claims on a blog. You asked for substance, well, I think they offered more than you did.

    Pleae correct me if I am wrong.

  22. Al Tekhasski Says:

    Now you admit that you have no expertise in IR spectrum instrumentation, so you cannot have any definite opinion, and you trust expert’s work endorsed by their peers in AGW climatology. Didn’t you know that the appeal to authority is a classic fallacy? That’s where you are wrong.

    Why do you need a peer review to understand that 25 spectra out of 1465 candidates are too few? Why do you need a peer review to request error bars on processed data? Why do you need a peer review to see that 6-year spectral difference is bigger than 27 year difference? Why do you need to “ferret out the CO2 signal” if the basic assertion in the movie is that “Earth is warming” because this article shows an experimental evidence that CO2 causes less OLR and global imbalance? Is there any all-sky imbalance?

    [Reply: Isn’t it an even bigger fallacy to just believe a guy on a blog above the considered opinion of countless experts? Check out this real skeptic: He writes: “It isn’t necessarily fallacious to consider that thousands of climate scientists writing in peer reviewed journals might know more than you do about such a complex subject. What we have here is trust in the scientific method. And we trust it because we have reason to believe it works – just look around you. (You’re reading this on a computer aren’t you?) And on a blog that promotes science and the scientific method, I’d have to be pretty perverse, or have a very good reason, to oppose thousands of peer reviewed scientific papers.” Again, extra-ordinary claims require extra-ordinary evidence. Handwaving is not quite enough. BV]

  23. ditmar Says:

    Back to the snowstorm/driving analogy the snowstorm seems to be a projected event by the met office and others(and as a brit we know how accurate their predictions are, my webber bbq is still in its wrapper). So you seem to advocate slowing down before the snowclouds have even formed. My view is the ipcc overstated the evidence as they knew the pdo shift leading to a cooler few decades meant that copenhagen was the last chance to get global agreement. Broken hockeysticks and climatgate ruined that. Folks who for years were told the science was settled now know it is not and trust in the science is lost. Climate scientists may never regain that trust. I have no doubt that agw proponents are praying for a huge disaster to befell some poor community as we speak, perhaps el nino will provide it. So excuse me while I stick to the speed limit I want to get home in case the weather changes. Cheers.

  24. ScP Says:

    Slow motion snowstorm – nice image, kind of ironic tho’ ;-)

    Smoking is not such a good metaphor. CO2 is not a pollutant, it is the stuff of life.

    Also CO2 has been in much higher concentrations in the past and the logarithmic effect is likely to mean that any increase of CO2 will not, in the next few decades be too devastating.

    However, moving to less carbon based fuel economy is a good thing. The big question is how do we get there? Bill Gates has the right idea I think.


    But while I believe we should focus on innovation, look at what the Enron inspired Carbon Trading scam has come up with – the WWF buying large areas of the Amazon rain forest so that they can earn $billion carbon credits – guess what the effect of this will be? Zero reduction in CO2 emissions. Appalling.


    To quote Bart – I’d love to be wrong.

  25. RickA Says:


    Thank you for your reply.

    If it was 6 degrees warmer in the last three interglacials and seas were 4-6 meters higher – why wouldn’t we expect the same during this interglacial.

    My question is why do we assume the next six degrees will be caused by humans – and not simply natural variation (like the last three interglacials).

    My concern is not on the impact of warming – but on the cause of the warming. I would like to make sure that we have the cause right before we make public policy.


    Thanks for your reply.

    If Antarctic was 6 degrees warmer – than the tropics were higher in absolute terms. The increase from ambient (in the tropics) might not have been six degrees – but it had to be warmer in the tropics than at antarctica.

    I still don’t understand why natural climate variation is not still on the table – given that it appears to be common to have temperatures higher than today and seas higher than today, during interglacials.

    Why is today different than 125,000 years ago?

    Science has said that they cannot explain the current warming – absent AGW – but I don’t see that – given the last three interglacials.

    Just wondering.

    [Reply: The same process that caused warming after an ice age (Milankowitch forcing aided by positive feedbacks from the carbon cycle and ice sheet albedo a.o.) is definitely not responsible for the current warming, since it operates on timescales some two orders of magnitude larger. The strong response of sea level to only a relatively small change in temp (globally 1-2 deg warmer) however (again, after long timescales) is not comforting however. BV]

  26. Marco Says:


    Could you please provide evidence that it was six degrees warmer during the last three interglacials? The last one, yes, but you may also notice that the current interglacial has a completely different profile:

    Moreover, climate scientists can quite reasonably model the various temperature increases based on the Milankovitch cycles. And according to those, we should be going down…

  27. RickA Says:


    See the first comment to this thread – in which I say that I rely on this letter:

    I am basing this off this letter to Nature:

    Nature 462, 342-345 (19 November 2009) | doi:10.1038/nature08564; Received 9 October 2008; Accepted 5 October 2009
    Evidence for warmer interglacials in East Antarctic ice cores – which indicates: “that the available evidence is consistent with a peak Antarctic interglacial temperature that was at least 6 K higher than that of the present day — approximately double the widely quoted 3 +- 1.5 K.”

    This letter refers to three different interglacials having a temperature at least 6 K high than today in the antarctic.

  28. Marco Says:

    OK, you are taking one paper as evidence. Doesn’t change the fact that we’ve long passed the normal peak of an interglacial (see the graph I linked to).

  29. RickA Says:


    The point of the letter to Nature is that the conventional wisdom (shown in your graph) of 3 degrees K +- 1.5K is wrong and it actually got to 6 K warmer than present.

    So “normal” interglacial peak turns out to be twice as high as shown in your graph.

    Which is my point – how do we know that the current warming isn’t natural?

    If we have warmed to 6 degrees warmer at least three times before – why is this interglacial any different than the last three?

    Occam’s Razor indicates that the simplist explanation is most often correct. It seems to me that the simplist explanation to explain the current warming is natural variability. It complicates things to rely primarily on CO2.

    The warming started prior to the increase in CO2 from 280 ppm to 385 ppm.

    CO2 levels have been shown to follow temperature increase, with a lag of 500 – 800 hundred years – not the other way around.

    I am sure that humans are contributing to warming – but have no idea how much of the current warming is natural and how much is caused by human activity. I don’t think our current science has yet nailed this down either.

    Until we can nail that down better scientifically – it seems to me that we should not make public policy – especially based on climate models which are not validated.

    [Reply: gotta love this quote from Deltoid in answer to the CO2 lag argument: See also my forthcoming paper: “Chickens do not lay eggs, because they have been observed to hatch from them”. BV]

  30. Scott Mandia Says:


    You need to visit Skeptical Science or my shorter list of false claims.

  31. RickA Says:


    Thank you Scott. I looked at your shorter list – and in particular your blurb on CO2 lags temperature.

    I understand your belief that everything changed after the industrial revolution.

    However, how do you explain the fact that temperatures started up after the little ice age – before CO2 started rising. This is consistent with the last 650,000 years.

    So you have still not addressed my question of why the current interglacial is different than the last 3.

    Even if there were no people – one would expect the temperature to rise another 6 degrees C – just as in the last 3 interglacials.

    I don’t understand why everybody is so certain the temperature rise is 100% certainly caused by humans – and there is no possibility that it is natural.

  32. Scott Mandia Says:


    I do appreciate that you view links when suggested. The LIA was more regional, BTW, with much smaller cool anomalies globally than in Europe. The thinking goes that this period was influenced by a weaker solar forcing and an increase in volcanic activity. After the LIA, these cool forcings abated.

    See this link from Skeptical Science:


    I think the issue might be the time scales that you are discussing vs. the time scales that are critical for AGW forcing. Milankovitch cycles are on the order of 41,000 and 100,000 years while AGW forcing is decadal.



    Of greater concern is that humans may be trumping the Milankovitch cycles and we may never see the next ice age at the rate we are going.


    Click to access TargetCO2_20080407.pdf



  33. Marco Says:


    It’s one place on earth that the +6 is reported. Think about it.

    Also, climate scientists can do calculations based on the Milankovitch cycles, giving quite reasonable agreement in the timing of heating and cooling. We don’t expect any further heating based on that.

    You also seem to suggest that the current increase in CO2 is due to warming. This does not fit with the facts. We’ve seen about 100 ppm increases in CO2 upon many degrees of warming (at least 6) during the interglacials. We’ve already passed the 100 ppm with at best 1 degree of warming over the last century and no discernable large temperature increase in the last two centuries. Moreover, the isotope ratios show that the increase in the atmosphere is due to fossil fuel burning (also corroborated by a concomitant fall in oxygen concentrations). Finally, the observed increase actually means 50% of what we add by fossil fuel burning isn’t going into the atmosphere. This can hardly be due to massive extra uptake by plants (there’s no evidence of that), and thus most likely go into the ocean (which fits with observed ocean acidification).

    Oh, and please define “validated” for us. GCMs are checked against the whole last century, known short-duration events like volcanoes, and also against interglacials. Sounds like validation to me…

  34. RickA Says:

    Scott Mandia:

    Once the cooling forces abated – I assume some of the temperature rise from that point forward was “natural” in the sense that the temperature would naturally rise, once the cooling force was removed.

    That is what I mean when I say that some of the warming we are experiencing is “natural” and some is no doubt caused by humans.

    I don’t know the proportion of human versus natural warming.

    I am not sure science has a good handle on this yet either.

    I do agree that interglacial’s occur over a much greater time scale (thousands of years – even tens of thousands of years) than AGW warming.

    However, how can one tell the difference scientifically?

    Are we outside the range of normal interglacial temperature ranges?

    It doesn’t seem like we are.

    Therefore, isn’t it possible that the natural warming component could be greater than the portion caused by humans (increased CO2, carbon black, land-use, etc.).

    Of course, it is also possible that the natural warming component could be much smaller than the portion caused by humans.

    But what does science tell us about this proportion – it seems we have a great deal of uncertainty – which is caused by the fact that most of the warming has occured in the last 35 years.

    It seems to me that we need more data.


    Yes – the 6 degrees was only found in one place.

    However, that is because that is where the ice cores are.

    It would be great if we had 800,000 years of ice core data from the equator – but we don’t.

    It seems reasonable to assume that if the temperature rose to 6 degrees warmer at Antarctica, than the present – that it was also warmer at the equator (perhaps not 6 degrees but warmer than at present).

    Statistically validated means comparing the prediction of a model with actual observed data (future data not used to tune the model).

    See for example, Testing ecological models: the meaning of validation by Edward J. Rykiel, Jr. Here is a link to the abstract (the article is behind a paywall):


    There are a ton of literature references to statistically validating any computer model.

    Now I will be the first to admit that I am not a statistician. But it is my understanding that the only climate model we have currently which has been statistically validated (meaning it shows “skill”) is the hurricane prediction model.

    Not a single global climate model demonstrates “skill”.

    Perhaps they will in the future – but they do not currently.

    Therefore they are not statistically validated.

    How then can we rely on them to make public policy?

    [Reply: “However, how can one tell the difference scientifically?” You give part of the answer yourself: Different timescales. Different forcings. The extent of Pinatubo’s cooling was predicted before it was observed; Hansen’s 1988 projections were in the correct ballpark; tuning only gets you so far, since models are constrained by the physics and applied to simulate mutliple events. BV]

  35. Marco Says:

    If you would read the paper you yourself point to (it’s already in the abstract), “skill” essentially depends on what you *define* as the desired skill. Regardless, validation *is* performed on climate models and they show skill. They may perform poorly on some aspects, in particular wind speeds and precipitation. There are thus some areas that will be difficult to predict (apart from the difficulty to predict the future per se).

    But pointing to poor skill as a reason to NOT make policy is a rather dangerous proceeding. The less we know for sure, the more dangerous it actually becomes. In such cases you’d have to take the highest possible estimate as your starting point, since it is ‘as likely’ as the lowest possible estimate.

  36. Scott A. Mandia Says:

    I think this is where physics comes in and modeling helps to explain what has happened and what is likely to happen. Radiative physics is pretty well understood and the increases in CO2 will have warming outcomes and these are consistent with predicted values.






  37. RickA Says:

    Marco and Scott:

    Thank you for replying to my posts.

    Marco – I don’t believe that any global climate models have been shown to have “statistical skill”, as that term of art is used. So I think you and I are using different definitions of “skill”.

    What we need are testable predictions from climate models. Then wait 5, 10, 15, 20 or so years and then see if they are correct using actual observations. Then we will be able to validate climate models.

    I don’t believe the climate models from the 80’s or 90’s made testable predictions which are born out by actual observations – at least nothing that I have read in Nature or Science yet.

    Don’t get me wrong – I think it is possible that someday we will understand all of the inputs and their interactions to the point that we will be able to model the climate successfully – but I don’t think we are there yet.

    The next 25 or 30 years should make or break the current climate models – and I await the results eagerly.

  38. RickA Says:

    This is an example of bad logic:

    Action on climate is justified, not because the science is certain, but precisely because it is not

    Link: http://www.economist.com/displayStory.cfm?story_id=15720419

    One shouldn’t take action until a proper cost-benefit analysis has been done. Science needs to weigh in on both the costs and the benefits.

    We need more data.

  39. Scott A. Mandia Says:

    RickA, I agree that waiting another 30 years will give us more validation but that is comparable to telling a person who we think may have cancer to wait 30 years to see if it kills him. If we are right about AGW, we do not have the luxury of waiting. I wish it were otherwise.

  40. RickA Says:


    I understand your sense of urgency.

    However, the hypocratic oath is to first – do no harm.

    If you do not know if the patient is even sick – does it make sense to operate?

    [Reply: If 97 out of 100 specialists come to the conclusion that your child is slowly getting very sick, you better have very good reasons to put their opinions aside. Perhaps the cost of treatment is such a reason for you? But even then, that’s not a reason to judge those opinions as wrong. BV]

  41. Marco Says:

    If we wait 25-30 years and the climate models are even remotely right, we are 50 years too late. Yes, you read that accurately: 50 years too late. Jim Hansen made predictions in 1988, and we’re running nicely within his lower and upper bound of his predictions. Based on that he demanded action was to be taken. In 1988. Of course, prior to that we already had the Charney report which warned of significant warming. In 1979. Moreover, the IPCC *does* consider the climate models to have skill. Regionally there are problems with predictions, in particular wind speeds and directions and precipitation, which actually means that predicting *adaptation* is where the biggest uncertainty comes in. Not on the mitigation side…

    And if “do no harm” is your starting point, stop emitting CO2. We *know* it does harm.

  42. ScP Says:

    Moved as O/T (fingers crossed it is now on topic)

    Scott/Prof Mandia and Bart

    Not sure what you mean by an ‘acceleration of decrease’ in sea ice.

    Sounds more like ’skepticalscience.com’ which is really ’swallowitwholescience.com’

    My planet. Hope it is yours too ;-)

    And this – actually this might be too horrid to watch :-(


  43. Scott Mandia Says:

    Sea ice area is just one small piece. Sea ice thickness and mass are better indicators of gain or loss and mass is decreasing.

    Why just look at sea ice and not ALL ice? When one looks at the entire cryosphere, the planet is rapidly losing ice.

  44. ScP Says:

    So am I looking at the wrong graph?

    It was widely reported when we had the 2007 data that the sea ice decrease was accelerating (John at Skeptical Science still uses the old graph to make this point) but the latest data suggests that it is not accelerating.

  45. Scott Mandia Says:


    If you look at the entire record, even sea ice extent is rapidly decreasing. If you just look at sea ice in the past two years, then no, in fact extent is increasing.

    However, sea ice thickness and mass are decreasing and continue to do so. Old ice is rapidly diminishing which is why there may be an ice free summer in the Arctic in your lifetime.

  46. ScP Says:

    The graph please not a general homily – I do understand about sea ice mass.

    Either the graph is wrong or misleading or it is correct and the sea ice decrease is not accelerating. If it is not accelerating then why keep saying it is. (And why would arctic being sea ice free in the summer be a problem? It has been before.)

    The record (see the graph) looks reasonably stable – and that kind of data is deeply confusing to those reading alarming tales of how things are getting worse at an accelerating rate. It just does not look like that.

    Phil Jones on ‘no significant warming’ – I realise he is not saying it is not getting warmer -he believes in AGW – but it does look like whatever is happening is slowing.

    To say otherwise makes you look dishonest and as tho’ everything must be terrible/alarming/devastating. You wont win back public confidence and acceptance if you are not painfully honest.

    I have asked here before about the IPCC report and hurricanes and got no answer. The silence is helpful. I still feel you are evading the data on the graph.

  47. ScP Says:

    Sorry, I meant the silence is unhelpful ;-)

  48. Scott A. Mandia Says:

    The graph is not stable when viewed in its entirety. Look at how many years are below zero and how far below zero in the past decade compared to the previous ones. Then look how few are above zero and how far above zero.

    The anomalies are hard to discern because the y-axis is misleading. the range is a bit large to make it easy to view for the average person.

    Sea ice extent IS accelerating since 1979 but not in the past two years.

    I think you are confusing weather and climate. Trends in climate can only be determined over many years and any given subset of those years can yield misleading results.

    An ice-free summmer will have a positive feedback on global warming due to a lower albedo in that region. It is significant.

    One must also keep mind that the 2000s had a record weak sun so it is not suprising that the rate of warming slowed in the short term. 2009 was a very warm year and 2010 is likely to set a new record.

    The latest info regarding hurricanes:

    A recent paper published by some of the top hurricane researchers in the field (Knutson, et al. 2010) concludes:

    …future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6–34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre.

  49. Scott A. Mandia Says:

    Read this:

    Click to access global.sea.ice.area.pdf


    observed N. Hemisphere sea ice area is almost one million sq. km below values seen in late 1979 and S. Hemisphere sea ice area is about 0.5 million sq. km above that seen in late 1979, partly offsetting the N.
    Hemisphere reduction.

    There is a global decrease.

  50. Scott A. Mandia Says:

    Oops. in the 13:29 post I meant sea ice extent decrease is….

  51. ScP Says:

    Thanks Scott, agreed, but sorry to labour this – yes to the decrease, no to the acceleration.

    I cant see it no matter how hard I try! I must be myopic.

  52. ScP Says:

    And this

    “Much of the record breaking loss of ice in the Arctic ocean in recent years is down to the region’s swirling winds and is not a direct result of global warming, a new study reveals.”


    No denial of global warming, here, just a step back from alarmism due to new information.


  53. Scott A. Mandia Says:

    Yes, decrease is probably the best way to state this. Accelerating is certainly not clear. I will try not to use that word when I create a new misinformation page regarding sea ice extent. (I will be countering the claim that sea ice extent globally is flat or increasing.)

    Regarding the Guardian story, I have no problem with it. 1/3 of the extent loss may be due to winds which leaves 2/3 due to AGW perhaps? Again, thickness is likely to be a better indicator of warming.

    Being a meteorologist, I would never claim that weather doesn’t influnce climate. :)

  54. ScP Says:

    Brilliant. Agreed. Many thanks ;-)

  55. RickA Says:

    Another article from Scientific American which indicates that more CO2 is emitted from the soil:


    Again showing rising temperatures, if caused naturally, will also naturally cause a rise in CO2 emissions.

    Correlation is not causation.

  56. Scott Mandia Says:

    This is bad news if another “sink” for CO2 is now getting weaker. As the authors state: “If true, this is an important finding: that a positive feedback to climate change is already occurring at a detectable level in soils.”


    Humans are already causing a net increase of 18.4 Gt CO2 per year and growing.

  57. Scott Mandia Says:

    Climate Progress has a story on this new study.

  58. ScP Says:

    A nice list of predictions here


  59. Scott A. Mandia Says:

    You should put some of these on my Chopping Down the Cherry Tree thread. Lots of blue cherries on the c3headlines page.

  60. RickA Says:

    I found the Scientific American article interesting because it seems to confirm what the data have shown – namely that a rise in temperature causes a rise in CO2 – but with some delay.

    It makes sense that melting permafrost will release more CO2 and I guess I can see why faster growning plants will also increase CO2 (although I would think they would also fix more CO2 in roots and such) – but I guess the net might be an increase in CO2 being released.

    But normally – the temperature goes up and then the CO2 goes up.

    However, now people are saying that CO2 is going up and therefore temperature is going to go up.

    I am not sure that science has yet ruled out that the increase in CO2 is naturally occuring from a rebound from the LIA.

    Of course, I agree that humans are adding further CO2 to the atmosphere, over and above whatever amount is being release naturally.

    [Reply: That can indeed be ruled out. BV]

  61. RickA Says:

    BV: [Reply: That can indeed be ruled out. BV]

    Yes – you are right.

    I misspoke.

    I meant to say:

    I am not sure that science has yet ruled out that the increase in temperature is naturally occuring from a rebound from the LIA.

    [Reply: I guess in 1850 you could say something like that (see eg the number of sunspots over the past 400 years in this figure). To make the same claim in 2010 seems a very far stretch to me. BV]

  62. Peter Wilson Says:

    Scott Mandia says “Old ice is rapidly diminishing which is why there may be an ice free summer in the Arctic in your lifetime.”

    There already has been, Scott. I suspect you’re not, but I am old enough that this photo was taken in my lifetime

    Navy records state “Skate (SSN-578), surfaced at the North Pole, 17 March 1959.”

    We had all better panic, it might happen again!

  63. Peter Wilson Says:

    RickA said:

    I am not sure that science has yet ruled out that the increase in temperature is naturally occuring from a rebound from the LIA.

    [Reply: I guess in 1850 you could say something like that (see eg the number of sunspots over the past 400 years in this figure). To make the same claim in 2010 seems a very far stretch to me. BV]

    Bart, I am unclear how sunspot numbers relate at all to this proposition, nor why it is a stretch to suggest a rebound from the little ice age may still be occurring. After all, temperatures rebounded from a cool period into the middle age warm period over asimilar length of time, so why is it so implausible that the same thing is occurring (naturally) again?

  64. Peter Wilson Says:


    I think I get it now. You are suggesting that the Little Ice Age was caused by the lack of sunspots, and the rebound was therefore caused by the revival of sunspot numbers.

    Please confirm if this is correct, as I have seen many articles on consensus sites arguing that only oil funded deniers could possibly think the sun had anything to do with climate.

    [Reply: Low solar activity was a contributing factor in the LIA indeed; whether it was the only or most important one I don’t know of hand (volcanism as well if I recall correctly). And leave the strawman accusation at the door please. That (changes in) the sun is important for (changes in) climate is self evident and no climate scientist would deny that. (But if the sun doesn’t change, the effect fades away of course) Quite a few RC scientists have looked into solar variability, and I think also inrelation to the LIA (Schmidt and Benestad?). BV]

  65. Eli Rabett Says:

    Peter, there has been a major change in the past decade about our understanding of how sunspot number relate to solar irradiance. I don;t have any links handy, but the relationship is today considered much more indirect.

    Rick, there are attribution studies which show the increase in CO2 in the atmosphere is directly related to burning fossil fuels. Besides changes in C13/C12 ratios, Ralph Keeling has shown anticorrelated changes in oxygen mixing ratios, etc. As far as increased CO2 in the atmosphere, we done it.

  66. RickA Says:


    I agree that part of the increase in CO2 is due to humans. However, I also think part is natural, caused by the increase in temperature.

    I am not so convinced that the increase in CO2 is causing all of the temperature increase we have seen since 1850.

    I tend to believe that we overestimate the effect of CO2 (the climate sensitivity number) and therefore I believe at least 1/2 of the temperature increase is due to natural factors, with the other 1/2 due to humans.

  67. Eli Rabett Says:

    Rick, go read Ralph Keeling on the variation of O2 in the atmosphere for a sobering look. Also there is tons of stuff out there on the carbon cycle which shows that human emissions are more than enough to account for the increase in mixing ratio and forcing.

    Eli is rather fond of the bunnies bringing chocolate eggs too.

  68. Marco Says:

    A recent paper put the feedback factor (gamma) at about 7 ppm per degree warming. That would put the natural contribution to the observed increase at less than that value. CO2 has increased by 100 ppm. Conclusion? The most important contributor are human emissions.

    Regarding the observed temperature increase: you may want to read the IPCC report. It tells you something about the attribution of the warming, and you may note that early 20th century warming is related mainly to solar effects. The late 20th century…not so much.

  69. Peter Wilson Says:


    For once I would agree with you. Keelings data is beyond reproach, and there is little reason to suspect we are not the cause of the increase in co2 levels.

    Regarding the relationship between sunspots and climate, I think it it fairly clear that the observed relationship is considerably stronger than can be accounted for by conventional theory, and that some amplifying mechanism must be at work. In this regard the results of the CLOUD experiment being carried out by CERN will be of great interest, as to whether or not the results support the cosmic ray-cloud formation hypoyhesis identified with Svensmark. If it’s not that, it must be something else..

  70. Marco Says:

    @Peter Wilson:
    A paper to enjoy on a lonely evening:

    Click to access 500102001.pdf

  71. Eli Rabett Says:

    wrt CLOUD, the EPA has made an interesting point, CLOUD had a lot of problems with surface effects, maintaining a clean system and stable temperatures, that means that the earlier Svensmark experiments almost certainly were plagued by such effects because they were much less sophisticated. You can toss them

    AGW observer comes up with a study that show the variation in cloudiness in the ISCCP data is MUCH less than previously thought, which means that all of the claimed “correlations” with cosmic ray fluxes can be tossed also.

    Stick a fork in it, the cosmic ray stuff is toast.

  72. Peter Wilson Says:


    Thanks for that. no need to wait for the results of the experiments, thanks to you we know already.

    Science just gets easier and easier..

  73. Eli Rabett Says:

    No Peter, many experiments have already been done, the claimed motivation for the experiment has likely disappeared, and (follow the links links), much of the claimed support for the hypothesis has been falsified.

    However, if you want to continue tossing good money after bad, go ahead.

  74. Peter Wilson Says:


    Yes, a few experiments have been done, and the results have been quite suggestive, although far from conclusive

    CERN have had this strange idea that the best way to get to the bottom of this, rather than arguing about correlations with dodgy data, might be to actually conduct an experiment! Radical idea – these guys obviously are not real climate scientists!

    But of course actually carrying out experiments is a waste of money, as you point out, because we already know the answer. These guys at CERN are so stupid. Much better to spend the money on another conference in Bali>

  75. dhogaza Says:

    Thanks for that. no need to wait for the results of the experiments, thanks to you we know already.

    Science just gets easier and easier.

    You’re rather missing the point, which is that the CERN CLOUD experiments have been preempted by other work, the CLOUD experiments have not gone well (which is why you’re not seeing anything definitive coming from CERN as a result), that the difficulty that CERN’s had controlling cleanliness and sufficient temperature stability make it highly unlikely that Svenmark’s earlier attempts could’ve even matched their efforts to control the environment in which the experiment was taking place, etc.

    If you’d read Eli’s link, perhaps you would’ve gotten the point.

    Instead you’ve trivialized the response of the EPA without bothering to read it.

    Walk like a denialist, quack like a denialist, you just might be a denialist.

  76. dhogaza Says:

    More peter wilson:

    CERN have had this strange idea that the best way to get to the bottom of this, rather than arguing about correlations with dodgy data

    Where are the “correlations with dodgy data” in Solomon et al. (2007), Pierce and Adams (2009) (tee hee!), Erlykin et al. (2009), Carslaw (2009), Pittock (2009).

    Please be precise …

  77. Peter Wilson Says:

    More dhogaza

    Walk like a denialist, quack like a denialist, you just might be a denialist.

    What did you call me? How dare you! Please apologise for this disgraceful slur. I had relatives die in the holocaust, and find this type of pathetic insinuation utterly beyond the pale.

    Especially coming from a climategate denier!

    Why bother doing science, just smear your opponents. I submit that any use of the term “denier” be deemed a breach of Godwins law.

    Bottom feeder1

  78. Harry Says:


    You made a statement about the isotopic pattern. You do not have single iota of understanding of isotopic fingerprinting. Show me the calculations. No blabla, calculations.

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