A Few Things Ill Considered

Warming Stopped in 1998

Posted by coby on April 25, 2006
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This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.

Objection:

Global temperatures have been trending down since 1998. Global Warming is over.

Answer:

At the time, 1998 was a record high year in both the CRU and the NASA GISS analysis.  In fact, it was not just a record year, it blew away the previous record by .2oC. (That previous record went all the way back to 1997, by the way!) According to NASA, it was elevated far above the trend line because 1998 was the year of the strongest El Nino of the century. Choosing that year as a starting point is a classic cherry pick and demonstrates why it is necessary to remove the very chaotic year to year variability that exists (aka: weather) by smoothing out the data. Looking at the CRU’s graph below, you can see the result of that smoothing in black.

Clearly 1998 is an anomaly and the trend has not reversed.  (Even the apparent levelling at the end is not the real smoothing.  The smoothed trend in 2005 depends on all of its surrounding years, including a few years still in the future.)  By the way, choosing the CRU analysis is also a cherry pick because NASA has 2005 breaking the 1998 record, though by very little.

Now this is an excusable mistake for average folks who do not need the rigors of statistical analysis in their day jobs, but any scientist in pretty much any field knows that you can not extract any meaningful information about trends in noisy data from single-year end points. This is why it is hard to hear a scientist make this argument and still believe that they are a voice of integrity in this debate, rather it appears more to be an abuse of the trust people would like to place in them as scientists.  Bob Carter is such a voice and was the first to trot out this argument in an article in the Daily Telegraph.  Since then it has echoed far and wide and has been used by Richard Lindzen as well as a host of sceptic websites.  

Interestingly, Bob Carter seems to know what he is doing as he tries to pre-empt objections in his article by basically insinuating that any choice of starting point, (such as 1978), will just be a cherry pick with the opposite motive! But cherry picking is about choosing data for the sole purpose of supporting a pre-conceived conclusion, it is not the simple act of choosing at all, as one must choose some starting point. In the case of his example year, 1978, this is often chosen simply because it is the first year that satellite records of tropospheric temperatures were available.

So what choices are there, what are the reasons for those choices and what are the conclusions we can draw from them?

  1. As just mentioned above, one could chose to examine the last 30 years because that is the period of time where both surface and tropospheric readings were available. We have been experiencing warming of approximately .2oC/decade during this time.  It would take a couple of decades trending down before we could say the recent warming did in fact end in 1998.
  2. You could choose 1970 in the NASA GISS analysis as this was the start of the late 20th century warming and as such it is a significant feature of the temperature record. The surface temperature over this period shows .6oC warming.
  3. You could choose 1965 in the CRU analysis as this is when the recent warming started in their record. This record shows around .5oC warming of the smoothed trend line.
  4. You could choose 1880 in the NASA record. This shows .8oC warming.
  5. You could choose 1855 in the CRU record. This shows .8oC warming.  Again, with this trend and the above we can not say it is over without many decades more data all indicating cooling.
  6. You could choose to look at the last 500 years in the bore hole record analysis because that is its entire length. This puts today about 1oC above the temperatures in the first 3 centuries of that record.  The record of today’s trend in that kind of analysis will be hidden from view for many more decades.
  7. You could choose to look at the last one thousand years, because that is as far back as the dendrochronology studies reliably go. Then the conclusion is:
    Although each of the temperature reconstructions are different (due to differing calibration methods and data used), they all show some similar patterns of temperature change over the last several centuries. Most striking is the fact that each record reveals that the 20th century is the warmest of the entire record, and that warming was most dramatic after 1920.

  8. You could choose to look at the entire period of time since the end of the last ice age, around 10kyrs ago. Then the conclusion is that GHG warming has reversed a very long and stable period with a very slight downward trend and we are now at a global temperature not experienced in the history of human civilisation, the entire Holocene.  Such a long view applied to today will take many centuries to clear up.  The situation is a bit more urgent than that!

I think that about covers any periods of time relevant to today’s society. Clearly, "it has stopped warming" is only supported by taking a single specific year out of context and using a 7 year window to look at multi-decadal trends in climate. That is a classic cherry pick.

This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.

“Warming Stopped in 1998″ was first published here, where you can still find the original comment thread. This updated version is also posted on the Grist website, where additional comments can be found, though the author, Coby Beck, does not monitor or respond there.

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Comments

  1. #1 Tim Wells
    August 19, 2008

    No,”stopped warming” means just that.2001 or 2002 is when it stopped warming and 2007 and 2008 in particular show a strong fall.We are now back to the same temperature as around 1980.AGW predicts that as the co2 level rises temperature will rise.This has not happened since 2002,which suggests that co2 is not a primary driver of climate.

  2. #2 coby
    August 19, 2008

    Hi Tim,

    How about some kind of data to back up your wild claims? Please provide a temperature record showing 2007 or 2008 at the same level as 1980.

    Thanks.

  3. #3 Chris,Baildon
    August 21, 2008

    Coby

    Here is a copy of the UAH (University of Alabama, Huntsville) Microwave Sounder Unit (MSU) – it ends in July (can’t find the August one sorry)

    http://wattsupwiththat.files.wordpress.com/2008/08/uah_july_08.png

    This shows that the anomaly for 1980 is higher than the current 2008. Would this count as evidence for Tims wild claims?

  4. #4 coby
    August 21, 2008

    Hi Chris,

    Thanks for presenting something concrete. I guess I should have been more precise and specified seasonally averaged global temperatures, monthly fluctuations are too chaotic. But just eyeballing your graph (I’m sure I could google it, and am not doubting its veracity, but it is always nice to have the source handy for detail and explanation) it is clear that 2007 is not below 1980 and 2008 is not over yet. So strictly speaking Tim’s claim is still incorrect even if we ignore all of the other temperature records available.

    But let me ask you this: what would it mean if a single year did drop below 1980? There is very large inter-annual variability even in globally and seasonally averaged temperatures, these changes are really part of weather. Climate trends require a lot of time to determine. This is why the IPCC took until the late nineties to finally say “yes, the climate is warming” when looking back on the CRU graph above one might be tempted to say it was obvious in the early 80′s.

    I remember very well and not too long ago, sceptical voices saying it was too soon to say the climate was really warming even after the IPCC decided it was clear. Now these same voices are all too happy to seize on a mere 8 years to decide we are cooling! I have great difficulty believing the sincerity of such arguments. That said, I have no idea where you are coming from in all this and do not wish this digression to reflect on you personally!

    Thanks for the comment.

  5. #5 Tim Wells
    August 22, 2008

    The point of the discussion Coby was that warming stopped around 2002,and that 2007 and 2008 have seen a sharp fall in temperatures.According AGW theory the 5% increase in CO2 over the last decade should have resulted in more warming-it has not!What it does show is another example of the LACK of correlation between CO2 and temperature.Please present some clear evidence that CO2 has caused the current warm period.

    [Tim, there is no point conversing with you if you simply ignore everything put in front of you, it is in the article above: a 10 year trend is more influenced by weather than climate change. There are other guide entries about the strength of the correlation over this century. Please remember there are other influences, no one claims CO2 is the only factor. Look at the CRU graph, the trend has leveled off recently but there has been long term cessation or reversal yet.]

  6. #6 Chris,Baildon
    August 22, 2008

    Hi Coby – I’m happy to have reasonable arguments on any topic ;-)

    I agree with you that 8 years is not long enough for a long term climate trends – although it is intriguing. In the same argument is the 20 odd years of warming since the late 1970′s long enough? – when I believe CO2 was supposed to overcome the natural variability in the worlds climate.

    [Even 20 years is not long enough to be unequivocal. We do have, however, a 100 year long record to analyse.]

    I’m happy to admit the world has warmed slightly in the last 100 years. Increased CO2 in the atmosphere may well have something to do with it. Were I tend to start getting very sceptical is the “tipping point”, “we’ve got 10 years to save the world”, etc type scenarios. There always seems to be a “10 years to save the world” disaster about to happen.

    [I can't disagree that 10 years to act is a little arbitrary. I would say to be safe we should move as quickly as possible.]

    I’m happy to try and improve the environment and use more efficient things (its saves me money after all). What I’m not too keen on is destroying the world economy because some computer models foretell disaster – which would happen if we went back to the under 300 ppm on C02 – as Dr Hansen wants.

    [I think "destroy the world economy" is a tad alarmist, no? : )]

    I do not see how blaming the worlds climate woes on one politically amenable constituent (i.e. CO2) when the climate has thousands of variables (many unknown), is chaotic and does seem to have changed rather alot over the past centuries, will really make the world a better place.

    [But this is not at all a fair characterization of the scientific reality of our situation. Plus CO2 is hardly a politically convenient target, we all produce it in almost every economic activity and the biggest corporate and political powers are very heavily involved in the oil industry. No one decided first to target CO2 and second to build a fraudulent case against it.]

    Happy to be put right on any points – I’m just an interested layman.

    By the way if the Jevons paradox stays true — this drive for energy efficiency may have unforeseen consequences.

    [Maybe it will make us a happier and cleaner society ;-) ]

  7. #7 Tim Wells
    August 24, 2008

    Coby,you start off by sayin g that there is no use conversing with me because of…….
    Well,if you could show me the evidence that CO2 has caused our recent warming,I would be happy.I will repeat;there is no meaningful correlation between CO2 and temperature over any significant timescale.Please present your evidence!By the way,by admitting that “weather” or “aerosol pollution” can override the effect of CO2 you are simply confirming the fact that CO2 does indeed have a negligible effect on climate.Do you realise that?It is another way of saying that CO2 is NOT the primary driver of climate.

  8. #8 Tim Wells
    August 25, 2008

    Tim Wells wrote:”Please present some clear evidence that CO2 has caused the current warm period,”
    Coby replied:”Tim,there is no point conversing with you if you ignore everything put in front of you,it is in the article above.”
    Is it?Are you sure? Not only is there not any evidence about CO2 in that article,CO2 is not even mentioned ONCE!!

  9. #9 coby
    August 25, 2008

    Tim,

    It is a little confusing that you are making cross thread references in your comments. Please read the IPCC AR4, at least the summary for policy makers, all the evidence is there. If you don’t trust that summary, follow up with the references in there in the primary literature. I also highly recomment Spencer Weart’s “History of Global Warming”.

    by admitting that “weather” or “aerosol pollution” can override the effect of CO2 you are simply confirming the fact that CO2 does indeed have a negligible effect on climate.

    No, it only means there are other factors that can dominate on short timescales. Volcanic erruptions are another. CO2 clearly dominates on multi-decadal timescales this last 100 years or so. It is not an either-or, all or nothing proposition at all, but rather a complex interaction of many factors, CO2 being just one, albeit a very important one.

  10. #10 TimWells
    August 27, 2008

    Well I keep on asking but it is obvious that you can’t present any evidence.AR4 does not have it either,and I challenge you to post it here from the SPM.
    “CO2 clearly dominates on multi-decada timescales..”
    No it does not!We had global COOLING from 1940 to 1976 during the greatest period of economic expansion in history.That is almost FOUR decades,and CO2 did NOT drive up temperatures.And just to pre-empt you…..if you are thinking of saying that this cooling was caused by aerosols,then that simmply demonstrates that CO2 does not have a strong temperature signature,and it’s effect is negiligble.[which is what the science says!]In any case the aerosol theory is wrong.If the aerosols caused cooling then it should have had more effect[ie more cooling]in the northern hemisphere.It did not,as there was more cooling in the SOUTHERN hemisphere.Once again real world observations just dont match the theory!

  11. #11 botogol
    August 28, 2008

    the odd thing is – if you disregard all the text and just look at the top graph is *does* seem to look like warming has stopped, doesn’t it?

  12. #12 Douglas Barnes
    August 30, 2008

    Funny, now that you mention it, botogol, no, it doesn’t look like that at all.

  13. #13 coby
    September 5, 2008

    Tim,

    It did cool more in the NH than the SH mid 20th century. So by your own admission this is good evidence that the aerosol theory is correct.
    http://data.giss.nasa.gov/gistemp/graphs/Fig.B.lrg.gif

    And I just have to point out that aerosols temporarily dominating CO2 forcing does not imply CO2 forcing is insignificant, just that there are other factors and they need to all be assessed. They have been and over the last 100 years CO2 is the largest single factor.
    http://www.grida.no/climate/ipcc_tar/wg1/figspm-3.htm

  14. #14 tim wells
    September 19, 2008

    Coby once again these graphs are from James Hanson and have been shown by McIntyre to be doctored.There is a full expose about it on Climate Audit.

  15. #15 Brian D
    September 19, 2008

    Tim, the graph is from the Hadley center, which is unaffiliated with Hansen. He had nothing to do with that graph.

    If you can’t tell the difference between Hadley and GISS, how can you claim to be informed here?

  16. #16 coby
    September 19, 2008

    Brian, he’s talking about the links I provide just above. Not that it makes a difference to the argument, but here then is the same comparison from CRU:
    http://www.cru.uea.ac.uk/cru/data/temperature/nhshgl.gif

    For the 50′s, 60′s and 70′s the NH trend was down, while the SH trend was up. This is consistent with the explanation that NH air pollution caused cooling until 70′s pollution controls came into effect.

    ClimateAudit has shown no such thing about Hansen, though they did helpfully uncover an error that changed nothing fundamental about the record.

  17. #17 shoegazer
    November 2, 2008

    Tim Wells: No Tim, your argument is a strawman type argument and as Coby asserts a classic cherry picking of data. Indeed, while I haven’t done the analysis, I’m fairly certain given the yearly variation present in the climate record that the past 8 years would not represent a deviation in a statistically meaningful sense from the preceding warming.

    Moreover your argument is irrelevant because you point to global temperature anomalies since 1998 remaining constant or falling slightly, point to C02 rising and then suggest it somehow refutes the theory. It does no such thing.

    the theory for AGW does NOT assert that climate is ONLY driven by GHGs, it asserts that GHGs are having an impact on climate and is resulting is warming. That doesn’t mean that the numerous other variables that are part of the climate play no part, they do, yet you focus on only ONE variable, infer some sort of linear relationship between the two, instead of a complex one with feedbacks, and then erroneously claim this refutes AGW. It’s absurd and shows a profound ignorance of climate science and modeling.

  18. #18 timwells
    November 3, 2008

    Shoegazer,I did not suggest that the AGW theory is ‘refuted’ by that last 8 years of stasis/falling temps.I said it suggests that CO2 is not a primary driver of climate.If AGW theory is right and CO2 is responsible for ‘most’ of the temperature rise,then what has caused the stasis/falling in temperatures since 2001,while CO2 has continued to go up??This observational evidence is not consistent with the theory.Something has apparently turned off the CO2 ‘warming driver’.If you have an explanation I am all ears.
    “you focus on only ONE variable…” NO,rather I focus on ONE CLAIM!!That claim is that CO2 has produced most of the warming,and so far the evidence supporting that claim is both sparse and inconsistent.

  19. #19 timwells
    November 3, 2008

    Coby thank-you for providing the temp graphs from CRU.Even the breifest of glances confirms my original assertion-that is that there should have been more cooling in the northern hemisphere,and there was not.Temps dropped faster AND farther in the Southern Hemisphere from 1940.The aerosol theory is supposed to produce the opposite!!If the aerosols were to produce cooling,then why didn’t the greater[and more rapid]cooling happen in the Northern Hemisphere?This also strongly suggests that the cooling was not produced by the aerosols which,by your own admission,were mainly a NH phenomenom.As such,I fail to see how these graphs support the aerosol theory as you state it.

  20. #20 paul
    November 3, 2008

    So shoegazer, if I understand correctly, when the temps go up between late 1970s and late 1990s, it is just as clear as day, and not even worth discussion, that this was due to human CO2. But when they level off not for an insignificant amount of time but for half the length of the “preceding warming”, something unlikely given the model predictions, suddenly things are very complicated and to even request an explanation of this behaviour is to be ignorant of science and modelling.

  21. #21 shoegazer
    November 8, 2008

    Tim Wells: Tim NO ONE has suggested GHGs were the ONLy driver or even the primary driver of warming.In fact I would venture if you asked any climate scientist the PRIMARY driver of climate is the SUN.

    The AGW theory is that GHGs are causing warming that would not have occurred due to natural factors alone and that that contribution is resulting in warming, which poses a danger to the planet as it exists today.

    Thus Tim since there are numerous variables that impact climate, it is entirely consistent with the theory and modeling to have GHGs increase but temperatures not increase and the reason is that changes in the other variables have likely occured. Now IF GHGs increase ceritus paribus – all other variables remain the same – then this could suggest some dynamic or variables not being accounted for, which warrants further investigation.

    There are variables, such as many of the aerosol forcings that exist, which act in a cooling manner on climate. It’s entirely possible that there factors are contributing more.

    Actually Tim the evidence isn’t sparse at all. The current state of the art models of climate demonstrate quite clearly that the warming observed during the 20th century can only be explained by the inclusion of GHGs. That doesn’t mean GHGs are the primary driver of climate, it means they are contributing to excess warming.

  22. #22 shoegazer
    November 8, 2008

    Paul: If you take the models and hold all other variables constant, other than allowing changes due to feedback effects and then allow the models to predict for warming driven by GHGs, you can ‘isolate’ the effect of GHGs on climate, especially the contributions due to human activity.

    To test the impact of changes in the variables on climate you need to run multiple scenarios. There are a number of studies that show that given a variety of climate models which all make slightly different assumptions, all show that warming of the 20th century can only/principally explained by GHGs.

    Regarding the cooling observed during the 20th century from 1945-1975, there are a couple explanations, which likely account for the pause in warming during that period. One there is an article in New Scientist which discusses some errors in the measurement of ocean temperatures during this period in the post WWII years. See the following link

    http://environment.newscientist.com/article/dn14006-buckets-to-blame-for-wartime-temperature-blip.html

    There is also a general consensus that aerosol cooling contributed to the pause in warming observed during this time. A greater degree of cooling was observed in the Southern Hemisphere than in the Northern which I beleive was a question Tim posed to Coby. Here are two possible explanations that might explain the observations:

    1. The following article refers to an increase in aerosol forcings during the 20th century and refers specifically to aerosol forcings climbing in the Souther Hemisphere. The others talk about aerosol forcings in general.

    http://www.pnas.org/content/104/14/5743.abstract

    http://www.sciencemag.org/cgi/content/summary/300/5622/1103?siteid=sci&ijkey=qJ.H5wzwcBWT.&keytype=ref

    http://www.nature.com/nature/journal/v435/n7046/full/nature03671.html

    2. The impact of desertification, which has been increasing in the Southern hemisphere, specifically South America. Deserts exhibit a much higher albedo than most other forms of land surface and the change to them has a much higher impact in the southern hemisphere due to the more direct incidence of solar radiation.

  23. #23 timwells
    November 10, 2008

    Lots of wonderful sounding theory Shoegazer,but not a lot of facts to back it up.
    Firstly,you are incorrect about the claims of CO2 being the primary driver.The IPCC says that “the majority of warming is very likely due to human activities”.In other words,CO2 is the primary driver of the recent warming.
    You actually state the same thing in your second paragraph above,so I fail to see what you are arguing about.
    The rest of your post is just about theory and modeling as opposed to real evidence.If temperatures dont rise when there is an increase in CO2,then it is because of “other variables”,not because the theory is flawed.So as such,what “other variable” has caused the stasis/cooling since 2001?Let me guess-you dont know!Infact you have written it with your own words.Here they are.
    “…have likely occured.”
    “…this could suggest..”
    “Its entirely possible..”
    In science Shoegazer,you have to do better than that.
    Also you seem to have the same problem that some other people have on this site in regards to what constitutes “evidence”.”The current state of the art models…” are NOT evidence my friend-they are just more theory!Evidence is real world data-try to understand that.
    Now you finish by claiming that “GHG’s….they are contributing to excess warming.” So exactly how much is this “excess warming” that you speak of?

  24. #24 shoegazer
    November 19, 2008

    Tim Wells: Well thank you Tim, now have you not only demonstrated your lack of understanding of the science, you’ve brought into question your ability at reading comprehension.

    I said that the primary driver of climate is the sun. Anyone who disagrees with that statement is either woefully ignorant or an idiot and I say that with about as much due respect as any such person would deserve.

    The AGW theory does not say that C02 is the primary driver of climate, nor the only driver, which is why there are numerous variables that (are included in) affect the climate (models) including but not limited to: insolation, water vapour, clouds, volcanic activity, earth’s axial tilt, precession, obliquity, aerosol compounds such as dust, sulphates, soot, etc. all contribute to global climate as does the earth’s albedo.

    CO2 is seen as the primary driver of recent warming above what one might expect from the natural parameters driving climate, not of climate overall. This has been demonstrated through models of climate where excess C02 buildup beyond the natural C02 cycle is included or excluded. Again only a facile level of understanding of the theory could allow one to conclude as you have that it implies C02 is the primary driver of climate. AGW theory says that ceritus paribus, manmade C02 increases are warming the planet on average over time. That doesn’t mean the average temperature has to respond as a smooth linear response variable to C02.

    Tim I have 4 degrees in science and engineering the highest being a doctorate. I’m also extremely well versed in the history and philosophy of science from Aristotle to Hume and onto Popper, so please don’t tell me how science works.

    All of science, every field is built on models. Einstein’s theory of relativity is a model, as are quantum mechanics, as are fluid mechanics, electromagnetism represented by Maxwells equations, etc.

    No Tim, I said that YOU make the error by assuming that if CO2 increases but global average temperature does not then the AGW theory has been refute. It does NO SUCH THING, such a belief represents an incredibly facile understanding of the science. NO ONE is claiming that global average temperature is positively linearly proportional to C02 and ONLY C02 which is the only way your assertion could be correct. There are numerous other variables. I used the words “could” because I haven’t looked at every single other data set to see if there are other input factors that could explain the “cooling”, but then neither have you since you discount them entirely.

    Data is JUST data Tim. It can suggest a model of nature which develops into a theory or it can falsify a theory if the predictions made by the theory don’t materialise. The latter has not occurred here. But it is the model, the theory that describes how nature works or how we believe it to work. Data is fine Tim but science relies on models of nature in virtual every field of scientific endeavour and engineers rely on them as well to design processes and products using our understanding of the theory/model of how nature operates.

  25. #25 paul
    November 20, 2008

    Shoegazer you said

    “I said that the primary driver of climate is the sun. Anyone who disagrees with that statement is either woefully ignorant or an idiot”

    “CO2 is seen as the primary driver of recent warming”

    “Again only a facile level of understanding of the theory could allow one to conclude as you have that it implies C02 is the primary driver of climate.”

    So, you seem to be either admitting that you are an idiot (though of course anyone with 4 degrees, who knows the highly relevant works of Aristotle and who uses phrases like ceritus paribus could not possibly be so) or saying that there is a difference between “recent warming” and “climate”. Could you explain what this is with clear English and numbers/timescales? That is, what is climate? When does the recent warming refer to? And how could something be driving “climate” but not be responsible for the recent warming, and vice versa?

    You also say about data that It can suggest a model of nature which develops into a theory or it can falsify a theory if the predictions made by the theory don’t materialise. The latter has not occurred here. and you also say NO ONE is claiming that global average temperature is positively linearly proportional to C02.

    In order to falsify a model with observational data, it has to make some predictions. As you are clear that AGW theory does not predict that temperatures will rise linearly as CO2 does, what exactly does it predict and how could it be falsified by observations?

  26. #26 Sergey
    December 2, 2008

    To Paul: Climate is not Global Warming or Climate Change. Check in Wikipedia.

    From Shoegazer’s message I understood that the primary driver of climate is the sun, and the primary driver of recent warming is CO2. Check in Wikipedia ‘Attribution of recent climate change’.

    ‘Recent climate change’, as I understand, is “instrumental temperature record of the last 150 years”. Check in Wikipedia ‘Instrumental temperature record’.

  27. #27 paul
    December 3, 2008

    Sergey ‘ I’m sorry, I tried to reply constructively but can’t, as the lack of clarity I pointed out in the last post simply continues.

    As for saying “it must be true, Wikipedia says it”, I’ll just politely ignore that. And could you point out where I said Climate is Global warming or Climate Change please?

    You are saying that Climate is not the same as two things I never said it was the same as, but have completely avoided the question I asked. You simply restated almost the same thing – “primary driver of climate is the sun, and the primary driver of recent warming is CO2″. Yet you STILL didn’t answer my question ie. ‘what is ‘climate’? When does the ‘recent warming’ refer to? And how could something be driving “climate” but not be responsible for the recent warming, and vice versa?”.

    You did say

    “‘Recent climate change’, as I understand, is “instrumental temperature record of the last 150 years”.

    Now, I never used the phrase ‘Recent climate change’, so maybe you meant to say ‘recent warming’. In passing I would say that that doesn’t make any sense anyway – how can a theory based on an interpretation of the data and the record of the data be the same thing? But do you mean the human contribution only or all of the change? If you are lumping the temperature rise of last 150 years together as climate change, then I think this is a confusing misuse of language, to be charitable – then we need another word/phrase for the ‘recent’ alleged human induced warming.

    And, taking your definition, I’m even more in the dark as to the difference between climate and recent warming ‘ how on earth could something be responsible for the warming of the last 150 years and not be considered to be driving the climate?

    Can people here who want to debate please raise their game and speak precisely. And this is not semantics ‘ in my opinion, the inability to state the position you are trying to maintain in clear english is a direct result of the fact that it makes no sense. But feel free to prove me wrong.

  28. #28 kristof
    February 19, 2009

    It strikes me that paul does not want to understand some things he certainly would understand if he is any intelligent. Since I will assume that he is (being an engineer and stuff), I have to assume he is just being malicious. How can one otherwise truely say something like
    ‘And how could something be driving “climate” but not be responsible for the recent warming, and vice versa?’

    Note that this semantics discussion has no real value in this debate, despite the fact that you claim other wise. It is just nitpicking.

    So, about drivers which you don’t seem to understand.
    There are many drivers for the climate. The sun, Methane, CO2, ocean currents, nuclear wars, volcano eruptions,… The word ‘driver’ is actually not such a good choice. They all have the ability to drive the climate but most of the time they have balanced each other in some steady state regime. Of course this regime has and does change in time but when looking with the time scale of a human life they are mostly in balance. Let’s call them inputs for the climate. They drive all the time, but when in balance this driving does not change the climate. Driving however has the connotation of change in it, which in the case of such equilibrium is not the case.

    Now since the balance of CO2 has been upset, it apparently drives the climate towards a some new equilibrium. So all the inputs are still there and they all still influence the climate. Of course they will interact and play. Higher temperatures could(or will eventually) lead towards the releasing of methane from the melting permafrost. This could then act as another driver (although it is also a greenhouse gas and it drives the same way as CO2). If an input that influences the climate changes, then the climate moves to a new equilibrium (in this case it seems to be heading for a warmer equilibrium). Since CO2 changed, we easily speak of THE driver for the recent warming, but of course it is still only one of the many inputs for the climate. The sun is still another input/driver.

    If hope I reduced some of your word uncertainty, though I won’t keep my hopes up.

  29. #29 Peter Doidge
    February 20, 2009

    My attention was very recently drawn to the following.
    Tim Wells: “If the aerosols caused cooling then it should have had more effect[ie more cooling]in the northern hemisphere.[ ]It did not,[ ]as there was more cooling in the SOUTHERN hemisphere.”
    Surely this is incorrect.
    If Tim were to look at the IPCC’s Fourth Assessment Report, Chapter 3, Figs. 3.4 & 3.6, he would see SST and land-surface air temp. anomalies for the Northern and Southern Hemispheres for the period 1850 to 2005. In the NH, the anomaly peaks around 1940, falls within 10 years, and levels out till the mid-1970s, then begins its ascent. In the SH, there is also a peak around 1940, but the drop afterwards lasts much less- only a few years- and the line begins its upwards ascent by 1950.
    What in these data entitles Tim to claim that “…there was more cooling in the SOUTHERN hemisphere”?

  30. #30 Chris Dotson
    February 20, 2009

    You know, if you’re standing at about 1940 you could look at the graph above or from the http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif link and say, “My gosh, temperatures are up almost 0.5C since 1910! We’re all going to roast! There’s no way people will be able to live in 2009!”

    I think it’s clear the earth is warming slightly. I think it’s clear that CO2 can and probably does contribute to that to some extent. That’s not enough to convince me that we ought to spend trillions of dollars and lower our standard of living to ‘fix’ it. For that matter, as someone has already pointed out, does everyone really think that technological process is going to stand still for 100 years while the Earth ends?

    I see AGW as being very similar to Y2K. Just as with Y2K, there are real issues — pollution and wastefulness — and there are definitely some things that should be fixed. And just like Y2K, some people are fixing the things that need to be fixed and most of the people are standing around wringing their hands over non-issues or selling things that have no value.

    Fortunately, Y2K hysteria had an easily defined end date. Unfortunately, AGW doesn’t — no matter how many years go by without the world ending, the End of the World can always be right around the corner.

  31. #31 mikatollah
    February 21, 2009

    Chris,

    The problem with Y2K was the unknown. Everyone knew there was a problem, but people weren’t quite sure how it would play out. That led to the media speculation and the wing nuts coming out to use it for their own purposes. But that didn’t make the problem go away. Responsible people took action to make sure a programming glitch didn’t damage our computer infrastructure. You are trying to make a comparison of the 2000 wing nuts and people who today are following the science. It doesn’t work unless you are in total denial about the science.

    This was written to explain Y2K so that anyone can understand it… maybe it will help: http://www.fema.gov/kids/y2k.htm

    I think smoking is a better analogy than Y2K. In 1940 my grand parents can be forgiven for taking part in a seemingly harmless activity that everyone was doing. There was no health information available to them to suggest they were putting their health at risk by smoking. But the same can’t be said for me in 2009. I have grown up during a scientific consensus that warned me if I start smoking I’m likely to suffer from heart and lung ailments. So I would be a damn fool for picking up the habit. The same is true for AGM… while my grand parents can be forgiven for not recognizing the danger, I would be a dame fool for not seeing it today.

    People fear change… it’s the human condition. But we have to put our fears aside and make decisions about the future based on reality, not on wishful thinking or our world view. You doubt the scientific consensus about AGW, but you are absolutely convinced that mitigation efforts will ruin our economy. You reject the evidence and embrace irrational assumptions. A trait you share with other deniers on this list.

    Embrace the change. It’s coming whether you want it or not… look for ways to make money off of it. Change always creates new opportunities for those who can let go of the old ways.

  32. #32 Informed
    March 11, 2009

    Again and again I see the words ‘cannot be explained without anthropogenic influence.’ This implies that every other influence is very well understood. Is this the case? No. Not even close. We don’t know how many variables there are in the climate, other than that there are ‘a whole bunch.’ We don’t know how many, out of the ones we consider, we correctly account for. It’s nice to put faith in a computer program but please keep in mind that that’s all they are. They’re wrong, to put it bluntly. All computer models are. Are they wrong little enough to still be useful? That’s a matter for debate, but I think the answer is fairly clearly ‘no.’ We don’t even know how many variables there are. We don’t know how they all interact. The ones we do keep track of, there’s no way to know if we’ve got their relationships pinned down just right. Saying that computer models can’t simulate past behavior without humans ‘plugged in’ is pretty meaningless, I hope we all agree. It’s exactly equal to ‘our modelers couldn’t think of any other reason, even knowing that there must be variables not accounted for, and knowing that we may take the known variables in to account incorrectly.’ It’s sophisticated handwaving. Nothing more, nothing less.

    In fact, I’d very much like to see some concrete reasons why it’s permissible in the IPCC reports to use an average of different climate model runs? If it was separate runs of the same model with some values tweaked slightly, that’d be ok. But these are all completely different programs! What does the ‘average’ of them even mean? If you’re thinking ‘nothing meaningful’ you’re exactly right.

  33. #33 Adam
    March 11, 2009

    Saying that computer models can’t simulate past behavior without humans ‘plugged in’ is pretty meaningless, I hope we all agree. It’s exactly equal to ‘our modelers couldn’t think of any other reason, even knowing that there must be variables not accounted for, and knowing that we may take the known variables in to account incorrectly.’ It’s sophisticated handwaving. Nothing more, nothing less.

    That’s pretty delusional thinking. Model results that did not match observed data were adjusted, and the adjustments caused the model results to match observed data. It is, in fact, the exact opposite of hand-waving. Once your results start matching observed data, you can be fairly confident that the model is a good one.

    Please bother to read up on the science of climate modeling before you rant, it gets tiresome hearing the same stuff over and over again.

  34. #34 coby
    March 11, 2009

    In fact, I’d very much like to see some concrete reasons why it’s
    permissible in the IPCC reports to use an average of different climate
    model runs? If it was separate runs of the same model with some values
    tweaked slightly, that’d be ok. But these are all completely different
    programs! What does the ‘average’ of them even mean?

    Ensemble runs are used because of the large natural variability that exists in the system. There will always be an element of randomness. So what averaging does is give us the most likely trajectory the climate will take. As the time frame is extended the natural variability because less and less significant, but for periods of one or two decades it is significant enough to temporarily mask the underlying trend, something we have seen happen over and over during the last centruy. There are many temporary cooling trends, plateaus and accelerated warmings.

    It is is rather like trying to predict the accumation of rools of the dice. A single moddel run might see a couple of snake-eyes, no double sixes and an unusual number of other low rolls. Using that run alone would show an accumulation far below the expected 60 points of 10 rolls for example. If you average many runs of the model, the average 6 per roll becomes clear.

  35. #35 Informed
    March 12, 2009

    Adam:

    The fact that the models had to be tweaked to match the data is a dead giveaway, and is NOT a reason to suppose that your model is good. Say I have a squiggly line I’d like to model with five variables. I’m not sure how many variables there really are in the equation that determines that line, but I can only think of five. So I boot up my model with some initial values and some fairly well established relationships between them. I run my model. It’s off enough that it’s clear I didn’t get it right. So I go back to the code, and mess with the numbers a bit. Maybe I screw with variable A, but leave the rest the same as they were. I run it again. AH! closer! Better! So now I tweak B a little bit too. Dang, it got worse. Now I change D and E, as well as A. Now it looks closer! In fact it’s pretty damn good! Well now! I’ve got a model that’s correct! Do you see the problem with this line of reasoning? Just because you were able, after enough tweaking, to do a fairly good job of reproducing actual results DOES NOT MEAN YOUR MODEL IS EVEN CLOSE TO CORRECT. All it means is that you messed with the numbers enough to get it to sorta fit. This does not mean that your ‘messed with numbers’ are the right ones. With five variables this is glaringly obvious. I don’t know exactly how many variables a climate model uses, but I’ve heard the number 30 thrown around. That one can tweak a bunch of variables and get a manufactured squiggly line to look close to a ‘real’ squiggly line is nothing surprising. It in no way implies that the models are even close to correct.

    Coby:

    I understand exactly what you’ve said, and I agree. However, your dice analogy and the ‘getting rid of noise’ argument are only fine if you run the SAME MODEL a bunch of times. Or, if you like, throw the same set of dice a bunch of times. What the IPCC does is different. They compute an average of different climate models. Or, keeping with the dice analogy, the average of the ‘average’ value for sets of dice loaded differently. The fact that the average value of the average value for ten sets of dice loaded differently is 6.251 tells us absolutely nothing important. Running one model a bunch and reporting an average is sound. Throwing a bunch of different models (that take different processes in to account differently) together in to an average is meaningless.

    Also: Wouldn’t the eventual average come out closer to seven for the dice? Seven is the most likely number on any given roll… Haha something a bit more light hearted to ponder!

    [coby: D'oh! You got me on that one....]

  36. #36 Adam
    March 12, 2009

    Informed –

    So if comparing your model results to observed data is not the correct way to determine modeling accuracy, what is?

    To continue on the dice analogy:
    If you model a physical die in different ways (elasticity, center of mass, dimensions, etc. etc), then, yes, it makes sense to run the different models and compare them to each other. That’s the kind of thing we’re talking about. No one is suggesting that we compare models of a d6 to a d12.

  37. #37 coby
    March 12, 2009

    Adam, I think if you had phrased it to be clear that the models are adjusted, rather than the results are adjusted Informed would not be able to jump on that sentence (I know it should be obvious).

    Absolutely that is the only way you arrive at a useful model. Feed it empirical observations of forcing factors as inputs, compare model outputs with empirical observations of climate properties and behaviours, investigate and learn from the differences, improve your model and repeat.

    The state of the art models do a very good job of hindcasting the 20th century, predicting the temperatures of other planetary bodies, reproducing the major features of the glacial inter-glacial cycles and are continually being improved. The very general projection of 3oC warming in a doubled CO2 atmosphere is extremely well established by now.

  38. #38 Adam
    March 12, 2009

    Coby –

    Yeah, re-reading my post, I can see how I phrased it very poorly. That’s what I get for writing it quickly during lunch.

  39. #39 Adam
    March 12, 2009

    Informed –

    A longer analogy of why your concerns over the model are misplaced:
    http://www.scholarsandrogues.com/2007/07/23/anti-global-heating-claims-a-reasonably-thorough-debunking/#m19

  40. #40 Crakar14
    March 12, 2009

    Hi Coby,

    Hows it going.

    In regards to your previous post you said

    “Adam, I think if you had phrased it to be clear that the models are adjusted, rather than the results are adjusted Informed would not be able to jump on that sentence (I know it should be obvious).”

    Well we both know that is not correct, satellite and radiosonde both showed no hot spot and yet an error was found with the sat data that not only showed the atmosphere to be warmer but that it warmed over a period of time to match the models.

    Radiosonde thermometer data shows no warming but this data is ignored and instead the wind shear data is used to calculate the temp which coincedentilly now matches what the models predicted.

    The ocean buoy systems have shown the oceans are cooling not warming as the models predict, one scientist was quoted as saying “we are looking at the data because we suspect there is an error, once this error is found we are confident the data will match what the models predicted” And no i do not have a link to this quote but am looking if i find it i will post it for sure.

    Cheers

    Crakar

  41. #41 Crakar14
    March 12, 2009

    Found it (well not the original quote) but this tells you how the error in the buoys was found.

    http://earthobservatory.nasa.gov/Features/OceanCooling/page1.php

    To sum up the Argo buoys were measuring too cold so he compared it to really old data from “disposable buoys” and he found they were measuring too warm and then somehow came up with a fix that proved the GW models were right after all.

    The beauty of this fix is that not only did it solve the puzzle for Dr Willis who said “If you aren’t measuring heat content in the upper ocean, you aren’t measuring global warming.” but it also solved the problems faced by a few other scientists.

    So now rather than having multiple studies around the world struggling to find data to prove GW is real we now have all the proof we need. Mind you the way the error is explained is nothing more than “slight of hand”.

    One thing i do find disturbing however is that essentially for the whole time the Argo’s have been in use the sea levels have slowed or stopped rising

    http://sealevel.colorado.edu/

    which would indicate that the oceans have in fact cooled. Is’nt that why the oceans are acidifying? But hey lets not get the facts in the way of a good story shall we.

    So in summary we have sat, radiosonde and Argo buoy data proving the models wrong until “an error is found” an error that is never explained and changes everthing and lets not even begin with Hansen and his fiddle fingers.

    So Coby the data is continuously changed to suit the models. No matter how strong your faith you cannot deny this.

    Cheers

    Crakar

  42. #42 Adam
    March 13, 2009

    Crakar,

    If you’re intent on seeing a conspiracy, nothing I or anyone else says could possibly convince you otherwise.

    You see a global conspiracy; I see scientists refining and updating their methods to continually improve their understanding. Objections were raised, errors found, and the corrections met expectations. I completely fail to see how you can judge that GW is a myth from one article that discusses error-correcting in one specific type of data collection. To use the colloquialism, you’re tossing the baby out with the bathwater. To use another analogy, it’s like saying evolution is a hoax because Darwin was wrong about inheritance.

  43. #43 Paul in MI
    May 10, 2009

    Geez . . .
    based on current global temperatures and those for the last 8 or 10 years, someone must have left out a minus sign in the model somewhere?

  44. #44 Patrick
    May 28, 2009

    Coby, your illustrations are missing. Can you fix this? If you have the time of course.

    Cheers

  45. #45 coby
    June 4, 2009

    Thanks Partick, that’s all fixed up now.

  46. #46 Ken Lambert
    June 4, 2009

    Coby wrote: “The state of the art models do a very good job of hindcasting the 20th century, predicting the temperatures of other planetary bodies, reproducing the major features of the glacial inter-glacial cycles and are continually being improved. The very general projection of 3oC warming in a doubled CO2 atmosphere is extremely well established by now.”

    Hindcasting the 20th century and reproducing the ‘major features’ of the interglacials is not that great is it? I would think that a pretty accurate ‘hindcast’ of the last 8000 years would be required to sort out the CO2 driven component from the background ‘noise’ of all the other climate drivers.

    [coby here:

    I am not sure why you think it would be required. It would certainly be great to have enough data to do this and we would undoubtedly learn a lot, but the central problem is not one of inadequate models, it is inadequate data to feed them. There was no global temperature monitoring, no annually resolved GHG inventories, no satellites watching the sun or measuring the tropospheric temperatures, no careful monitoring of land use changes etc etc.]

    Proving the warmest temperatures in 500 years proves nothing. We were coming out of the little ice age which bottomed in about 1650AD (360 years ago).

    [coby:
    Agreed, it does not prove anything. It is just more evidence consistent with the theory. Please see the LIA article and the no proof article.]

    Ian Plimer reckons that the Medieval Warming was warmer than now, and that the Earth has a history of glaciation existing with CO2 levels far higher that the current 387ppm.

    [coby: Why on earth would you trust Ian Pilmer?]

    Perhaps we should talk about Antarctica – the supposedly biggest knob on the Earth’s
    thermostat. Some scientists are finding cooling for 30 years in East Antarctica which is 4 times bigger than West Antarctica where it is supposedly warming. AGW theorists have found warming all over. Climate models all predict warming at both poles. At 90% of the Earth’s ice, Antarctica is the big game in town. Coby, what is going on here?

    [coby:
    The antarctic is isolated by the circumpolar current and is not actually expected to warm as much at this stage. It is also influenced by significant ozone depletion (this loss is a cooling influence). There is no significant discrepancy between (uncertain) observations and model predictions]

  47. #47 coby
    June 5, 2009

    Hi Ken,

    Please see replies inline. Thanks for the comment!

  48. #48 Vernon
    June 5, 2009

    Coby,

    the warming stopped, even the raise in sea level has gone back to the “AGW period” rate.

    Cazenave et al (2008)
    http://sciences.blogs.liberation.fr/home/files/Cazenave_et_al_GPC_2008.pdf
    This can be summarized as follows: since 2003, sea level has continued to rise but with a rate (of 2.5 +/−0.4 mm/yr) somewhat reduced compared to the 1993–2003 decade (3.1+/
    −0.4 mm/yr).

    Ablain et al (2009)
    http://www.ocean-sci-discuss.net/6/31/2009/osd-6-31-2009.html
    These new calculations highlight a reduction in the rate of sea level rise since 2005, by ~2 mm/yr. This represents a 60% reduction compared to the 3.3 mm/yr sea level rise (glacial isostatic adjustment correction applied) measured between 1993 and 2005.

    Cabanes et al (2001)
    http://www.sciencemag.org/cgi/content/abstract/294/5543/840
    The 3.2 ± 0.2 millimeter per year global mean sea level rise observed by the Topex/Poseidon satellite over 1993-98 is fully explained by thermal expansion of the oceans. For the period 1955-96, sea level rise derived from tide gauge data agrees well with thermal expansion computed at the same locations. However, we find that subsampling the thermosteric sea level at usual tide gauge positions leads to a thermosteric sea level rise twice as large as the “true” global mean. As a possible consequence, the 20th century sea level rise estimated from tide gauge records may have been overestimated.

  49. #49 vernon
    June 6, 2009

    Why is it that we are not to accept that warming peaked and we have begun cooling? The AGW period was from 1978 to 1998, so that was really not climate, just weather, right?

    We know that the rate of sea level increase has dropped back to the “average” rate for the 20th century. We know that Argus buoy system shows that the seas are not warming. We know that rate of sea level increase has decreased.

    What is not being talked about is that all the other cooling periods had a reason that could be pointed to, mainly volcanic eruptions, but this cooling period does not. That is real 800 lb gorilla in the AGW room that is not talked about.

  50. #50 SemiChemE
    June 19, 2009

    Back in 2006 when this article was originally written, I would have completely agreed with its precepts. At that point we had 30 years of warming. Sure there was a big spike in 1998 that didn’t really fit the trend, but otherwise there had been a pretty steady rise, so a couple years of flat temperatures couldn’t really be called a trend. However, here we are three years later and the temperatures still have not risen. In fact they appear to be down. So, we have a 5-10 year flat to down cycle, which is starting to be significant compared to the previous 30 year warming cycle. While I’ll concede that it’s too early to declare a definitive end to warming, there has clearly been a shift from the previous 30-year trend.

  51. #51 Richard Simons
    June 20, 2009

    SemiChemE: the temperatures may appear to be down, but I think if you take any recent ten year period of climate data, from any source, and actually calculate the regressions you will find that it has never been negative. The high value for 1998 gives a powerful optical illusion.

  52. #52 Loren
    August 9, 2009

    Can you help me understand why there is a correlation between global temperature and CO2?

    What really confuses me is the long term data that goes back hundreds of millions of years back to the Cambrian Period when CO2 levels peaked at 7,000 PPM to modern day where they are only a few hundred. The CO2 levels have no correlation to global temperatures whatsoever. Temperature and CO2 levels vacillated all over the place, but there is clearly no correlation.
    [p]
    However, during the last few hundred years of Earth’s evolution the claim is that there suddenly is a correlation.

  53. #53 ayoung
    August 9, 2009

    According to a recent opinion survey, man-made global warming is viewed as settled science among the majority of computer software developers in the United States.

  54. #54 Rik C
    November 26, 2009

    15

    Tim, the graph is from the Hadley center, which is unaffiliated with Hansen. He had nothing to do with that graph.

    If you can’t tell the difference between Hadley and GISS, how can you claim to be informed here?

    Posted by: Brian D | September 19, 2008 10:37 AM

    ————————————————-

    Well, we now know that there WAS connection to Hansen, as Hadley-CRU was committing fraud and fudging data, and all kinds of graphic and math tricks to make the data conform to what they PRE-DETERMINED the result should be!

    Are you ready to admit that the Hansen/Hadley-CRU/IPCC connection is what has been driving temps up, and not anthropogenic CO2?

  55. #55 Larry Hamilton
    March 5, 2010

    I sometimes teach statistics, so the recent media/blogosphere misinterpretations of Chris Jones’ remarks about statistically nonsignificant short-term “trends” looked like a teaching opportunity — for my students, if not for less educable pundits.

    Anyway, I wrote a short program to calculate trends in GISTEMP global temperatures over the period 1880-2009, then 1881-2009, 1882-2009, and so forth up to 2007-2009 (a three-year “trend”). The trends (regression slopes) all are positive and statistically significant for starting years up through 1996. They remain positive but nonsignificant through 2001. After 2002 the slopes turn negative but with confidence intervals that go far above zero as well as below.

    Here’s a graph of the whole series, GISTEMP 1880-2009:
    http://img.photobucket.com/albums/v224/Chiloe/LH_climate/global_temperature_3b.png

    Here’s how it looks if you cherry-pick 2002 as your start date:
    http://img.photobucket.com/albums/v224/Chiloe/LH_climate/global_temperature_4b.png

    The “trend” goes slightly positive if we start just one year earlier, in 2001:
    http://img.photobucket.com/albums/v224/Chiloe/LH_climate/global_temperature_5b.png

    And becomes steeply positive if we start in 2000:
    http://img.photobucket.com/albums/v224/Chiloe/LH_climate/global_temperature_6b.png

    But of course short-term trends are missing the point with respect not only to climate, but to statistics as well.

    Here’s a graph showing all the trends (slopes) versus start year:
    http://img.photobucket.com/albums/v224/Chiloe/LH_climate/Temperature_trends_1b.png

    And here’s a similar graph visualizing how confidence bands explode as you shorten the time window:
    http://img.photobucket.com/albums/v224/Chiloe/LH_climate/Temperature_trends_2b.png

  56. #56 Eike
    April 6, 2010

    Loren: Do you know the difference between absolute and relative warming? Good. Now, the period preceding the Cambrian was exceptionally cold. Almost the entire surface of Earth was frozen over. Clearly, other climate factors caused this – there was no higher animal life, there was no terrestrial vegetation. The main suspect is plate tectonics – land warms and cools more rapidly than ocean water, so it’s continental movements to or away from the poles (with their polar night/day) which will cause a switch between warm ages and ice ages.

    The Cambrian represents a period of rising CO2 and drastic global warming, *compared to the time preceding it*. Or *relative to the tectonic situation*. How can you say “there is clearly no correlation”?

    Also consider later periods: CO2 was usually above today’s levels, climate was warmer (in the mid-Mesozoic it was drastically warmer), with the usual consequences: Europe was mostly covered by a coral sea, as were the central USA. Suzch is the world in a period of exceptionally high CO2 levels, and even though we did have the usual Milankovic variations – cool and warm periods -, as it was a warm age back then, “cool period” did not mean “ice all over Central Europe” as we had it just 15000 years ago, but merely “a few mountains in Antarctica had glaciers”.

    Nowadays we are in an ice age. Many contrarians are sloppy with their language, and use “ice age” for what is actually a “glacial”, a period of ice advance, no matter whether in an ice age or warm age. We are in an interglacial in the current ice age (which started in earnest a few million years ago). That’s why Scandinavia is not covered in glaciers entirely (as it would be if we would be in a glacial period), but there are some glaciers (there would be none if we were *not* in an ice age).

    Then, there is the known property of CO2 (and other greenhouse gases) of capturing heat radiation. If this radiation is travelling in a specific direction (in our case, it is always travelling away from Earth), the effect of having GHG in the atmosphere is to block part of the surplus heat we receive from the Sun. The consequence is that increasing GHG content of the atmosphere must cause *some* amount of global warming, *relative* to the temperature immediately preceding it. Either that, or the laws of thermodynamics are dead wrong.

    We have been unable to refute the laws of thermodynamics since 150 years (when the first studies by Avogadro, Arrhenius et al found that there were indeed such laws, even though they lacked the maths to correctly express them at that time). We have also seen that temperature rise may cause atmospheric CO2 levels to increase, but that peaks in atmospheric temperature *always* appear to occur immediately following peaks in atmospheric CO2 (this last part is often omitted by contrarians. If you see someone mentioning only the “CO2 follows temperature” part, you know that person is dishonest). Also, extremely high global temperatures are apparently impossible to achieve *without* extremely high GHG levels.

    So there is and always has been a quite pronounced correlation. Plate tectonics is of course the stronger factor and can – as in the Precambrian-Cambrian case – overrule CO2. That’s why one speaks of climate “forcings” – a specific climate factor need not have an *absolute* influence, but it *always* forces the trend in a particular direction. GHG force it up. Having all continents stuck together at the South Pole would force it down, down, down.

    The bottom line is that:
    * the entire history of human civilization has taken place exclusively within a single interglacial in an ice age.
    * you would NOT want a switch from ice age to warm age. It would necessitate more people dying than anyone could stomach, because sea levels would rise so grossly as to flood much of the interior of all continents: the Solnhofen archipelago, the Turgai Strait, the Oceans of Kansdas, the Erromanga Sea; you might want to look these up to see what it’s like in a warm age.

    From a purely “humans-first” perspective, we would want the present interglacial to continue indefinitely, with a very, *very* slight warming trend (to increase global precipitation and temperatures).

    Problem is: the extra CO2 we added is – purely based on thermodynamic considerations – already good for about half the difference between a glacial and an interglacial. At least. This does not mean that we will see exactly this effect – other forcings also come into play – but it means that CO2′s effect on climate is probably more pronounced today than it ever was since the early Permian.

    As an evolutionary biologist, one cannot help but be disgusted by people like Lomborg with their “global warming is GOOD” stance. Their ignorance of good science permeates everything they say – but many of these people, including Lomborg, are economists, and as such they couldn’t foresee the global recession we’re in now. That is not science; a proper scientist should be able to make predictions about the future that are well-reasoned and turn out to be accurate. In any case, humans are not reptiles. Meaning that we cannot be expected to thrive in a warm age. Indeed, it was only the turn from the Mesozoic-Paleogene warm age to the current ice age that brought about the mammal-dominated world of today; had this not happened, we would probably have a civilization of intelligent birds by now (birds are better able to cope with very high temperatures than mammals).

    So, you do not want pronounced global warming – in the short run, you do not want it for your real estate property values, in the long run, you do not want it for your species. We thrive best in an interglacial within an ice age, and our ability to adapt to anything else has not yet been tested but given the extinction rates every time such climate shifts happen, it is not necessarily high even with all our inventiveness. At the least, we won’t be able to cope without forced resettling of many 100s of millions of people. I for one do not want this.

    (I have noted that most of the inability of many people to grasp the problem is a problem of size. The amounts of energy pertinent to the issue are mind-bogglingly large, and though air weighs next to nothing, so is the total mass of the atmosphere.

    What does help is to grab
    * a good record of atmospheric CO2 levels
    * a good record of atmospheric temperature
    * a Google Earth paleomap overlay, such as http://bbs.keyhole.com/ubb/ubbthreads.php?ubb=showflat&Number=624709&page=1

    and compare them. If one accounts for plate tectonics, the correlation between atmospheric CO2 and global temperature/habitable landmass should be strikingly obvious.

  57. #57 Bill
    November 12, 2011

    Isn’t it increase like 1% ever 50 years or so. Is this really something to worry about? I dunno enough about the issue to comment heavily but I just feel it’s not the end of the world.

  58. #58 Richard Simons
    November 12, 2011

    Isn’t it increase like 1% ever 50 years or so.

    CO2 or temperature?

    CO2 is currently increasing at over 0.5% per year.
    If you are going to talk about percentage increase in temperature, it only makes (some) sense to use Kelvin, in which case a 1% increase is about 2.9C (more than 5F), not a trivial matter when it comes to global averages.

  59. #59 Wow
    November 14, 2011

    “Why is it that we are not to accept that warming peaked and we have begun cooling?”

    Because it isn’t shown to be cooling?

    That would be a good reason for not accepting warming peaked.

    Ask yourself: why would this be a peak? Temperatures don’t act like a struck jelly, you know.

    “The AGW period was from 1978 to 1998″

    Why? What happened over that period that we did that we’re not doing any more?

    And why, if the “AGW period” ended 1998, have there been at least three and probably five years that have been as warm or warmer?

    Do you know what “peak” means?

  60. #60 Pollywantsa
    November 16, 2011

    I agree with Coby in that no matter what time period you use it can always be construed as a cherry pick. So where does that leave us?

    We can argue about whether warming has stopped or not but neither side can claim victory.

  61. #61 Wow
    November 16, 2011

    You can use statistical analysis to find out what period you need to take data over to display signal more than noise.

    Guess what. WMO did that. They figured 30 years.

    So go ahead and pick a 30 year running mean and calculate the trend for that 30 year period, year by year.

    And a cherry pick isn’t picking a year. A cherry pick is picking a year to get a desired result. You can deduce a cherry pick by picking several nearby numbers and seeing if the result changes significantly. If it does, it was a cherry pick.

  62. #62 mandas
    November 16, 2011

    Prett sure Coby didn’t say that no matter what time period you use it can be ccnstrued as a cherry pick.

    I think polly’s reading skills are right up there with his/her ability to do statistics and science.