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It's the sun
Climate's changed before
There is no consensus
It's cooling
Models are unreliable
Surface temp is unreliable
Ice age predicted in the 70s
We're heading into an ice age
It hasn't warmed since 1998
Antarctica is cooling/gaining ice
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Global warming and natural climate change in the past

The skeptic argument...

Earth's climate has changed long before we were pouring CO2 into the atmosphere. Europe was far warmer in the Middle Ages. During the 17th and 18th century, it was much colder, prompting the ‘The Little Ice Age’, when the Thames was frozen over months at a time. Further back, there were times when the Earth was several degrees hotter than current temperatures. Warming of several degrees often took only centuries or decades.

What the science says...

The usual drivers of natural climate change have shown little to no warming trend since the 70's.

It's a well established fact that climate changes naturally and sometimes dramatically. The pertinent question isn't "has climate changed in the past?" (of course it has) but "what is causing global warming now?" To begin to answer that, it's helpful to look at the major causes of natural climate change in the past.

Solar activity

Solar variations have been the major driver of climate change over the past 10,000 years. When sunspot activity was low during the Maunder Minimum in the 1600's or the Dalton Minimum in the 1800's, the earth went through 'Little Ice Ages'. Similarly, solar activity was higher during the Medieval Warm Period.

However, the correlation between solar activity and global temperatures ended around 1975. At that point, temperatures started rising while solar activity stayed level. This led a team of scientists from Finland and Germany to conclude "during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source." More on the sun & global warming...

Milankovitch cycles

Earth's climate undergoes 120,000 year cycles of ice ages broken by short warm periods called interglacials. The cycle is driven by Milankovitch cycles. Long term changes in the Earth's orbit trigger an initial warming which warms the oceans and melts ice sheets - this releases CO2. The extra CO2 in the atmosphere causes further warming leading to interglacials ending the ice ages.

For the past 12,000 years, we've been in an interglacial. The current trend of the Milankovitch cycle is a gradual cooling down towards an ice age.


Volcanic eruptions spew sulfate aerosols into the atmosphere which has a cooling effect on global temperatures. These aerosols reflect incoming sunlight, causing a 'global dimming' effect. Usually, the cooling effect lasts several years until the aerosols are washed out of the atmosphere. In the case of large eruptions or a succession of eruptions such as in the early 1800's, the cooling effect can last several decades. Strong volcanic activity exacerbated the Little Ice Age in the 1800's.


The usual suspects in natural climate change - solar variations, volcanoes, Milankovitch cycles - are all conspicuous in their absence over the past 3 decades of warming. This doesn't mean by itself that CO2 is the main cause of current global warming - you don't prove anthropogenic warming by eliminating all other options. But the primary causes of commonly cited climate change in the past have played little  part in the current warming trend.

As for CO2, empirical observations show that CO2 has a warming effect as a greenhouse gas, CO2 is increasing in the atmosphere and the expected warming you would get from greenhouse gases is occuring. Any alternative theory that found a different cause of global warming would also need to explain why the expected (and observed) warming from CO2 has not eventuated.

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Comments 1 to 50 out of 121:

  1. Again it is not correct to provide graphs like this without error bars, doesn't make sound science!
    [ Response: A response to this is posted here. ]
  2. Thanks for trying to answer science with science. Most sites on the subject are propaganda vs science or propaganda vs propaganda.
  3. Here is some more
  4. You might also enjoy this guy as a skeptic, at least he is also in the comics business. He draws too much attention to every noise he observes non-stop in the climate system, but some of the things we had in his book do seems to have credible logic attached to them, although as a non professional some of his arguments are not so justified:
    [ Response: Actually, I use as the example of the skeptic argument on We're heading into an Ice Age. But I've been contemplating replacing it with an excerpt from a more reasonable source - the website is so extreme, it's not a very good example of the skeptic argument. ]
  5. From the above site I found the following paper by Australian Prof, there it described the data quality/error bar issue.
  6. Will Nitschke ( at 11:25 AM on 22 December, 2007
    Your graph shows that all previous Milankovitch cycles were warmer or at least as warm as the current cycle. It also shows that when temperatures rise, CO2 increases.

    "The extra CO2 in the atmosphere causes further warming"

    Maybe, although the best science we have at the moment suggests the opposite: the atmosphere warms, then CO2 levels increase. This is not disputed, so you should correct the mistake here in your article.

    The open question is whether the CO2 release then creates a feedback loop that *then* causes further warming. That's possible, but many would argue not proven.
  7. "Strong volcanic activity exacerbated the Little Ice Age in the 1800's...."

    The usual suspects in natural climate change - ..., volcanoes, ...conspicuous in their absence over the past 3 decades of warming. "

    That's not a well worded argument on your part.- A. McIntire
  8. "It's a well established fact that climate changes naturally and sometimes dramatically. The pertinent question isn't "has climate changed in the past?" (of course it has) but "what is causing global warming now?"

    Thats not the pertinent question. The pertinent question is "Is their any evidence that industrial-CO2-release is BAD for the environment"

    The answer is that there isn't. All extant evidence testifies to the very great benefits of industrial-CO2-release. So not a single dollar of cost imposition ought to be contemplated.

    This is the biggest case of wrong-way-Corriganism that stupid humans have ever attempted to foist on their fellow man.

    The ludicrousness of worrying about some tiny amount of human-induced warming during a brutal and pulverising ice age is baffling to say the least. It can only really be explained in terms of political factors like the collapse of the Soviet Union and the never-ending exploitive pull of the tax-eating classes.
  9. Some remarks from someone who has been thinking about the CO2-issue since 1975 (when West-German Chanceler Helmut Schmidt advocated a shift to plutonium-breading nuclear reactors as a means to reduce CO2-output).

    All sources of fossile carbon are of biological origine. Coal, peat, oil and gas were once part of living organisms and originally in the form of CO2 in the atmosphere or in the oceans. When this carbon became fossilised, it was removed from the life-cycle and lost. By burning fossile fuels we put this carbon back into the atmosphere and restore part of the CO2 that was lost (lots of carbon is in the form of limestone, which is another issue).

    Its fruitless to argument if man causes climate change or not, what will happen is that we use up all fossile fuels during the next 200 years. Nothing can stop us. To stop this process we would need a global stop on the production of coal, oil and gas. But all I see is an intensification of production.
    All actions so far (Kioto-protocol, wind and solar energy etc.) do not address the primary production of fossile energy. Nobody even has proposed a control of this production in order to reduce it to a sustainable level.
  10. Wondering Aloud at 08:58 AM on 4 January, 2008
    Still Herr Schmidt's proposal could cut CO2 production from human sources by about 50% in North America, it would save a lot of money, greatly reduce land fill and other pollution problems. In short a better solution to the problem than Kyoto and any possible successor could possibly be.

    So why aren't we discussing it?
  11. Wondering Aloud at 09:07 AM on 4 January, 2008
    "But the causes of the commonly cited climate changes in the past are understood"

    Ok now that statement I disagree with very strongly. Because we have a working hypothesis on what may have caused the ice age cycle does not mean that we understand the climate changes in the past. You should just remove that sentance it damages your entire argument.
  12. "It's a well established fact that climate changes naturally and sometimes dramatically. The pertinent question isn't `has climate changed in the past?' (of course it has) but `what is causing global warming now?'"

    "Thats not the pertinent question. The pertinent question is `Is their any evidence that industrial-CO2-release is BAD for the environment'"

    Yeah, yeah. To the denialist, every question is pertinent except when it's not. If the question of "what is causing global warming _now_" isn't pertinent, then I wonder where we got all the "it's the sun" or "it's methane" or "it's ozone" or "it's China and India" talking points in the first place?

    This whole "that's not the pertinant question" bullcrap is just a handy tactic for denialists to dodge questions when confronted with the facts -- it's been described as the "Gish Gallop":

    -- bi,
  13. frankbi

    Excellent article. However it has nothing to do with AGW. Creationists and Environmental fanatics come from the same source. One worships the bible the other worships the earth, neither is credible. Fanaticism closes the mind.

    Science requires an open mind. It requires that you question everything and everyone. We all know that climate change is a reality. We all know that there is AGW. What nobody seems to be able to pin down is exactly what combination is causing the current warming. Hiding your head in the sand and shouting it's CO2 over and over does not prove anything any more than saying god did it proves anything. Cite a paper that does not play with "best fit" or uses real unaltered numbers to prove your case and it will be fact. Until then, all we have is a hypothesis. Thus far I have not seen a case either for or against CO2 as the prime AGW factor that has not manipulated the numbers in one direction or the other.
  14. The planet has been getting warmer for about 400 years according to the Vostok ice core data. There are many credible sources that show that human activity (AGW) has no significant influence on average global temperature. The temperature change that has been directly measured needs to be put in context with the proxy estimates of paleo climate. NOAA and other data show that the current climate is not unusual. Graphs of this (all referenced) are shown at
  15. Dan Pangburn
    If your scientific claims in: -
    are really so compelling and scientifically sound, we can look-forward to them being published in a respectable scientific journal, such as Nature or the proceedings of the National Academies of Science. Of course, this isn't going to happen, because your analysis is a flawed, pseudo-scientific diatribe relying upon repeated cherry-picked data to achieve a politically predetermined conclusion, unsupported by the evidence.

    Your political bias is revealed by such phrases as "de facto censorship by Climate Scientists", "group-think ‘consensus science’" and “These actions put freedom and prosperity at risk.” What is your evidence for each of these claims?

    Like many politically motivated denialists, you have deliberately relied-upon conflating weather and climate to draw conclusions that are unsupported by a competent analysis of the data. The chaotic weather fluctuations mask the underlying warming from increasing CO2, just as waves on the sea mask rising sea levels.

    You are using straw man arguments to prove your point – climate scientists are not claiming that CO2 is the only driver of the climate. The climate is driven by numerous feedbacks and forcings and your failure to find vastly over-simplistic correlations only proves your lack of ability, but does nothing to prove your case.

    If you really want to be taken seriously, don't cherry pick, or use fallacious arguments, just stick to the science and ditch the politics.
  16. ScaredAmoeba

    The data is all from NOAA and other credible sources. It is revealing to see it graphed. All of the data sources are referenced so the data can be checked. None of it is ‘cherry-picked’. Only global average temperatures are used which avoids ‘chaotic weather fluctuations’. The graphs facilitate the observation of trends. The recent (last 120 years) of NOAA data are very consistent with Hadley (They use different base temperatures. NOAA uses the average for the 20th century and Hadley uses the 1961 to 1990 average which is about 0.1C warmer). My observations are not based on the last ten years but include (from proxies) thousands, even millions of years. The recent data (last 120 years) plotted on the same graph as the Vostok data back to 1000 years ago shows that the current temperature and rate-of-change are not unusual.

    I started researching this subject more than a year ago because available information was conflicting and I wanted to find the truth. I started out with the perception that, given the handbook data that carbon dioxide absorbed infra-red radiation, more of it in the atmosphere would be expected to cause global warming. The credible data, however, showed that this perception was wrong. Extensive search failed to reveal any data that showed that added greenhouse gas caused global warming. The prediction of warming as a result of carbon dioxide increase comes only from Global Climate Models which are admitted to account poorly for clouds and fail to include other known factors.

    The very popular perception of a greenhouse gas blanket trapping heat and causing the planet to heat up is totally wrong. Anyone who perceives that greenhouse gas increase causes global warming has been mislead by a misunderstanding or ignorance of the physics of radiation heat transfer in a greenhouse gas. This is readily understood by anyone with even modest experience in optical spectroscopy but apparently is unknown to many climate scientists.

    The reason why increased greenhouse gas level has no influence on average global temerature is proven at and is summarized as follows:

    A gas is called a greenhouse gas because it has spectral absorption lines that cause it to absorb infra-red radiation at these specific spectral frequencies from objects at earth temperature. What is usually unknown to scientists who are not knowledgeable in the field of optical spectroscopy (e. g. many climate scientists) is that the absorption at the spectral frequencies by atoms (the gas is transparent at non-spectral frequencies) is nearly all within about five meters of the radiating surface and is very nearly all immediately transferred to nearby atoms by thermal conduction (the atoms bump into each other). Beyond a few meters from the surface, the greenhouse gas acts much the same as a non-greenhouse gas and the absorbed heat is carried up by convection currents. More greenhouse gas means only that the absorption takes place even closer to the ground. The convection process is unaffected. The end result is that climate is unaffected by increase in the amount of greenhouse gas.

    Although the average global temperature has been trending down for the last ten years or so it could still go higher again like it has four other times during the Holocene. The atmospheric carbon dioxide level is certain to continue to increase. It just won’t have any influence on the average global temperature.
  17. Dan Pangburn
    Your argument sounds reasonable but I am not great at math (my strenght has always been logic, I program the math into my computer). I read a paper by Gerhard Gerlich that I thought was strange and was told by another poster here was bad math. Now I am confused. Are you saying that he is correct?
  18. Quietman
    This has more to do with knowledge on which argument and logic can be based. Possibly the disconnect has occurred because most climate scientists are not educated in the science of optical spectroscopy. Yes, Dr. Nicol is correct.
  19. John
    An update on climate history from Harvard-Smithsonian Center for Astrophysics press release indicates that the little ice age and the MWP were global phenomena.
  20. Warm Penguin Eggs at 21:37 PM on 3 June, 2008
    It's interesting to note the style of attack used by frankbi and scaredamoeba.

    Rather than debating the scientific points, I see the same phrases coming up again and again: deniers, denialists, political bias, and some vague attempt to discredit the sources, such as "cherry picking" or "it isn't in these particular journals therefore it isn't valid".

    "Insubstantiated points"? I think you'll have to do better than that. What do you think will happen if a massive raft of new taxation is imposed everywhere to modify behaviour away from CO2 producing activity? We won't know for certain unless it's done and observed over a period of years so that economically anomalous periods can be averaged out. The idea of trying to enforce very costly modification to lifestyle is such a serious one that you had better be certain that the science is sound. The precautionary principle really isn't enough, especially when it seems that there are simply so many voices shouting this supposed 'consensus' at us who specifically seem to sidestep the real points of debate. I'm no scientist but I can see when posts have scientific substance, and are argued on the basis of logic and reason.

    When it comes to political bias, I would love to see an analysis of general political persuasion, comparing the "deniers" with the environmentalists. I would be interested to see whether the latter to be largely comprised of those who make a general opposition to capitalism and globalisation.
  21. Warm Penguin Eggs
    Re: "general opposition to capitalism and globalisation"
    Are not these concepts at odds with each other?
  22. A change or two in climate history has recently been revealed indicating change happens faster than thought:

    Fossils Found In Tibet Revise History Of Elevation, Climate
    ScienceDaily (June 12, 2008) — About 15,000 feet up on Tibet's desolate Himalayan-Tibetan Plateau, an international research team led by Florida State University geologist Yang Wang was surprised to find thick layers of ancient lake sediment filled with plant, fish and animal fossils typical of far lower elevations and warmer, wetter climates.

    Greenland Ice Core Analysis Shows Drastic Climate Change Near End Of Last Ice Age
    ScienceDaily (June 19, 2008) — Information gleaned from a Greenland ice core by an international science team shows that two huge Northern Hemisphere temperature spikes prior to the close of the last ice age some 11,500 years ago were tied to fundamental shifts in atmospheric circulation.
  23. John
    There is another, rather scary, factor that I have been discussing at the ABC news forum. The reply from a college professor that I have been debating AGW with is below (the question regards pole shift and magnetic field reversals):

    "why do you feel that this will be a reversal?"

    Because the SAA is strengthening and all models to date show a core mixing flip. The geological record shows a pattern of magnetic pole reversals and that the earth is due (has been for awhile) for another. Other magnetic anomalies will begin to pop up here and there over the next few hundred years then a long period of multiple magnetic poles until there is a pole flip. The timeline is on the order of a couple of thousand years then a few hundred thousand years of the north magnetic pole being in the southern hemisphere.

    Birds that navigate by magnetic lines may have a bit of a problem navigating multiple poles and may need to reverse their breeding habits. At any rate those that can adjust their breeding habits will survive. We may have a rough time too as the magnetic field zeros out. The aurora may be all over the sky at some point then stop for a long period of time. Without a magnetic field in place, the solar wind will blow on the surface of the earth for awhile. I really don't know if human life is in for trouble or if we will adjust, as usual. We may be able to shield ourselves somehow. (I wold not highly recommend a political or religious bad attitude toward science right now) (I certainly don't expect J.Z. Knight, Zantha, and friends to believe us out of this future)

    I certainly can't say one way or another when or where or why but this is the results of some geophysics research . The magnetic pole wandering and discontinuities have been continuous for as long as geo-magnetic records have been kept. The discontinuities are correlated with major earthquakes and the daily wandering may be correlated with microseisms (the continuous seismometer noise).
  24. I realize that this has not been discussed here but if pole reversals can affect climate it would appear relavent to this thread. I can not find any information on the web in this regard except for a few articles that indicate a recent pole shift towards Siberia.
  25. John

    Re: "Volcanic eruptions spew sulfate aerosols into the atmosphere which has a cooling effect on global temperatures."

    While true of continental volcanos or volcanic islands, those that do not break above the surface of the oceans have different consequences entirely. What would normally be aerosols are contained within the ocean. The outgassing, heat and particulates and ACIDS from these have a direct effect on the water.
  26. Dan Pangburn's post raises an interesting point that 'appears' to answer a current anomaly.
    If the major problem is CO2 (or any GG) then we should see warming at middle altitudes, but the present satellite data seems to present a case for no.increase/slight cooling.
    So we should only see warming at surface levels...which looks to be the case.
    So if GG's act more like a buffer zone within 5m of ground zero or any large radiating structure,then by plotting data at 10 m above selected weather stations should enable us to see if such variations exist...or am I missing something?
  27. Re; Quietman's comments regarding magnetic field shifts.

    If you check this site: you will find a bar chart of MF reversals which (for me anyway) has big red warning sign. There were NO reversals during the cretacious period and it was during this period that life 'exploded' into a multitude of forms and habitat. There are many possibilites here, one of which is that the earths' MF has a (unquantified) effect on the stability of climate by it's moderation of solar radiation; in other words we have another factor in the model.
    A generalised discussion can be found at;
  28. Sorry, missed this one out:

    For an astrological site it actually does contain some interesting information and references when you filter out the rubbish.
  29. #23:Been looking at MRI scans which indicate a causal connection between nano-deposits of magnetite in human brain tissue and degenerative brain diseases. Why is yet unknown and so is its role. What is known is that whales,certain birds, bees, butterflies (ie: migratory species) also have magnetite in CNS tissue. One postulation is that this assists them to navigate using the earth's magnetic field. Experimants on homing pidgeons show they are unable to navigate with a small magnet around their necks.
    So a MF fluctuation or worse, reversal, could be a big problem to migratory species who use it and other life forms that depend on flowering plants.
    The current strength of the field is circa 0.5 gauss
    (cretaceous 2.5 gauss) and any diminution will allow more high energy particles to reach the surface with consequent damage to all living tissue exposed to it.
    Movement of, or variation in the strength of the field will definitely disrupt electronic communication systems.
    Maybe there will be little direct effect on our climate, but there could be other serious consequencies for life as we currently see it.
  30. Mizimi
    Interesting links. The lack of reversals during the Mesozoic is very interesting in itself. Thanks.
  31. Mizimi
    There was a piece done at Scientific Blogging about how solar activity can cause large changes in the speed and intensity of the solar wind. I can't remember if it was sunspots or flares or both but the South Atlantic Magnetic Anomaly allows the solar wind in general to have more effect and therefore would allow increased solar activity to have a greater effect when the shield is reduced or down completely.
  32. QM: look here for an overview...

    Note: without a magnetosphere, we would have virtually no atmosphere as it would be stripped away by the solar wind. So changes to the strength of the earth's magnetic field and it's orientation are very important!
    The number of charged particles entering the upper atmosphere, and their subsequent effects is a function of field density and orientation.
    Any ionising radiation entering the atmosphere has the potential to cause condensation of water vapour
    (dependant on other physical factors) and initiate cloud formation; so we have another example of fairly weak forces giving rise to very substantial effects.
  33. Mizimi
    Yes I have read those pages before. On the discussion page someone asked if there is a relationship with temps and was answered in the negetive. I disagree. In an article at scientific blogging I read that recent discoveries demonstrate that eruptions on the sun both increase the velocity and temperature of the solar wind. If temp is increased within the solar wind then it must also have an effect upon the earth (2+2 is usually 4). :)
  34. QM:
    I don't see an increase in solar wind temp would have any substantive effect on TSI here....given the time to transit sun/earth and the fact that the temp. of space is around 4K, I would expect most heat related energy to disappear before it got to us.
    Velocity is another matter. Transit time would be reduced and the total energy would increase allowing more particles to enter our atmosphere instead of being deflected by our Mag. field. Faster particles = more energy = higher levels of interaction = greater heat input.
  35. Mizimi
    That is exactly what I saw.
  36. Very interesting read here...haven't heard anything about water vapour feedback yet. Enlighten me if what i say is wrong but are the IPCC models flawed in that their water vapour feedback element is missing out on a rather unavoidable factor in gravity. Douglas Hoyt discusses here about how overestimated the water vapour feedback is in the IPCC models. I take the side of the devil's advocate and say that it seems the IPCC has jumped on a bandwagon and is trying to make it work their way...but it isn't.
  37. Re #36 Adamski,

    That's a very odd notion. Odd in two respects. First the enhanced atmospheric water vapour that follows enhanced greenhouse atmospheric warming has been directly measured [*] and some of the consequences with respect to surface humidity and precipitation patterns are already identified in the real world [**].

    Secondly, because the "gravity" notion raised in the dodgy website you linked to is a nonsense. Water vapor that partitions in the atmosphere does so according to atmospheric pressure and temperature. As the temperature of the atmosphere rises so does the water vapour concentration. Is this effect countered by gravity? Not to any significant degree. Atmospheric water exists in the atmosphere in the form of individual water molecules. The gravitational force acting on these molecules is extremely small and is opposed by the kinetic energy of the water molecules provided by the ambient thermal energy.

    It's only if the atmosphere cools a bit and the water vapour concentration rises above the saturation point, that gravity takes a significant macroscopic hold. Then water molecules "aggregate", the water vapour condenses, and gravity then has an effect (it rains!).

    So not only is the website trying to sell a ludicrous notion, but it's premise is contradicted by real world measurements (see [*] and [**] below.

    [*] e.g.:

    Soden BJ et al. (2005) "The radiative signature of upper tropospheric moistening" Science 310, 841-844.

    Abstract: "Climate models predict that the concentration of water vapor in the upper troposphere could double by the end of the century as a result of increases in greenhouse gases. Such moistening plays a key role in amplifying the rate at which the climate warms in response to anthropogenic activities, but has been difficult to detect because of deficiencies in conventional observing systems. We use satellite measurements to highlight a distinct radiative signature of upper tropospheric moistening over the period 1982 to 2004. The observed moistening is accurately captured by climate model simulations and lends further credence to model projections of future global warming."

    Santer BD et al (2007) "Identification of human-induced changes in atmospheric moisture content" Proc. Natl. Acad. Sci. USA 104 15248-15253.

    Abstract: "Data from the satellite-based Special Sensor Microwave Imager (SSM/I) show that the total atmospheric moisture content over oceans has increased by 0.41 kg/m(2) per decade since 1988. Results from current climate models indicate that water vapor increases of this magnitude cannot be explained by climate noise alone. In a formal detection and attribution analysis using the pooled results from 22 different climate models, the simulated "fingerprint" pattern of anthropogenically caused changes in water vapor is identifiable with high statistical confidence in the SSM/I data. Experiments in which forcing factors are varied individually suggest that this fingerprint "match" is primarily due to human caused increases in greenhouse gases and not to solar forcing or recovery from the eruption of Mount Pinatubo. Our findings provide preliminary evidence of an emerging anthropogenic signal in the moisture content of earth's atmosphere."

    Rind D et al (1991) "Positive Water-Vapor Feedback In Climate Models Confirmed By Satellite Data" Nature 349, 500-503.

    Abstract: "Chief among the mechanisms thought to amplify the global climate response to increased concentrations of trace gases is the atmospheric water vapour feedback. As the oceans and atmosphere warm, there is increased evaporation, and it has been generally thought that the additional moisture then adds to the greenhouse effect by trapping more infrared radiation. Recently, it has been suggested that general circulation models used for evaluating climate change overestimate this response, and that increased convection in a warmer climate would actually dry the middle and upper troposphere by means of associated compensatory subsidence1. We use some new satellite-generated water vapour data to investigate this question. From a comparison of summer and winter moisture values in regions of the middle and upper troposphere that have previously been difficult to observe with confidence, we find that, as the hemispheres warm, increased convection leads to increased water vapour above 500 mbar in approximate quantitative agreement with the results from current climate models. The same conclusion is reached by comparing the tropical western and eastern Pacific regions. Thus, we conclude that the water vapour feedback is not overestimated in models and should amplify the climate response to increased trace-gas concentrations."

    [**] e.g.:

    Zhang XB (2007) "Detection of human influence on twentieth-century precipitation trends" Nature 448, 461-465.

    Abstract: "Human influence on climate has been detected in surface air temperature(1-5), sea level pressure(6), free atmospheric temperature(7), tropopause height(8) and ocean heat content(9). Human-induced changes have not, however, previously been detected in precipitation at the global scale(10-12), partly because changes in precipitation in different regions cancel each other out and thereby reduce the strength of the global average signal(13-19). Models suggest that anthropogenic forcing should have caused a small increase in global mean precipitation and a latitudinal redistribution of precipitation, increasing precipitation at high latitudes, decreasing precipitation at sub-tropical latitudes(15,18,19), and possibly changing the distribution of precipitation within the tropics by shifting the position of the Intertropical Convergence Zone(20). Here we compare observed changes in land precipitation during the twentieth century averaged over latitudinal bands with changes simulated by fourteen climate models. We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel."

    Allan, R P & Soden, B J (2008) Atmospheric warming and the amplification of precipitation extremes" Science 321, 1481-1484.

    Abstract: "Climate models suggest that extreme precipitation events will become more common in an anthropogenically warmed climate. However, observational limitations have hindered a direct evaluation of model- projected changes in extreme precipitation. We used satellite observations and model simulations to examine the response of tropical precipitation events to naturally driven changes in surface temperature and atmospheric moisture content. These observations reveal a distinct link between rainfall extremes and temperature, with heavy rain events increasing during warm periods and decreasing during cold periods. Furthermore, the observed amplification of rainfall extremes is found to be larger than that predicted by models, implying that projections of future changes in rainfall extremes in response to anthropogenic global warming may be underestimated."
  38. Re #37 Chris, i have the other side to the story. Has any research been done on just how much water vapour can be held in the atmosphere and the warmer temperatures before it reaches saturation point? And also explain to me why Douglas Hoyt's info is so dodgy. He's fairly knowledgeable in the field so why is his contribution so wrong? How do we know what's right or wrong? You can justify comments with 'scientific proof' but how do we know that it is correct? Are you prepared to take anyones word for it? Is there some corruption not only from the climate change skeptics but also from the IPCC and other anthropogenic climate change supporters?

    It's all very interesting but doesn't everyone within this current issue have an agenda?
  39. Re #38 Adamski,

    interesting questions; some are easily answered, some less so:

    [Has any research been done on just how much water vapour can be held in the atmosphere and the warmer temperatures before it reaches saturation point?]

    It depends where you are in the atmosphere since the saturation level varies with temperature and pressure. These data are known quite acurately 'though. You can see the variation of saturation of air with water vapour as a function of temperature here (scroll down the page to find the relevant graph):

    [And also explain to me why Douglas Hoyt's info is so dodgy. He's fairly knowledgeable in the field so why is his contribution so wrong? How do we know what's right or wrong?]

    One can compare Hoyt's assertions with reality. They don't match. Therefore in this instance we know Hoyt is wrong.

    A problem is that Hoyt hasn't published anything on this. he's just asserting stuff on a web site. Since he may well have written it in 2004, perhaps he thought it was correct then but doesn't realize that real world data now contradicts his assertion; perhaps he just hasn't bothered to update his web site. We'd have to ask him...

    Hoyt has made the assertion (on his website) that gravity effects will eliminate 90% of the warming-induced enhancement of water vapour concentrations. The Minschwaner and Dessler paper that Hoyt refers to indicates a possibility of a much smaller reduction in enhanced water vapour. So even in 2004, Hoyt's assertion didn't match reality. Now we have much better measures of atmospheric water vapour, and it's clear that the atmospheric water vapour concentrations rise pretty much as predicted by theory and modelling. As well as the articles whose abstracts are listed in my post above, more recent analyses (see [**] below) of direct tropospheric water vapour demonstrate that the water vapour concentrations are rising in response to warming pretty much as predicted. So Hoyt is demonstrably wrong.

    [You can justify comments with 'scientific proof' but how do we know that it is correct?]

    It's not really about "proof". It's about the evidence. In this case Hoyt is making assertions that are directly contradicted by the evidence. So in this instance Hoyt is demonstrably wrong. A lot of the efforts in dealing with so-called "skeptical" (!) "arguments" is in pointing out their inherent self-contradictions.

    Hoyt is also wrong (it seems to me) on straightforward theoretical/empirical grounds that relate to the competing effects of gravity and thermal kinetic energy on isolated molecules in a vapour as I outlined in my post just above.

    [are you prepared to take someone's word for it?]

    Yes and no. If someone has a habit of dishonesty of course one would be foolish to take their word. Likewise if someone is respected for their honesty and diligence, I'm more likely to take them at face value. I am always skeptical of stuff that is asserted on this or that web site, and if one investigates further and finds that the asserter hasn't published the relevant work (or in this case hasn't published anything for 10 years), makes assertions that are not supported by any evidence, and upon further investigation, finds that the assertions are actually directly contradicted by real world evidence, then it would be foolish not to discount the assertions.

    One should be skeptical about these things!

    [Is there some corruption not only from the climate change skeptics but also from the IPCC and other anthropogenic climate change supporters?]

    Corruption is usually identifiable. Can you identify any IPCC "corruption"? I haven't come across any. That doesn't mean the IPCC are paragons of perfection! If anything the IPCC presentations are somewhat conservative.

    [It's all very interesting but doesn't everyone within this current issue have an agenda?]

    I wouldn't have said so. There's clearly a strong agenda position to misrepresent the science amongst certain quarters (you see quite a lot of it from a cohort of posters on this web site). In my experience the only "agenda" the scientists have is to get to the bottom of whatever topic their researching, preferably making some good discoveries along the way and publishing some well-respected and highly-cited papers.


    Gettelman A and Fu Q (2008) “Observed and simulated upper-tropospheric water vapor feedback” J. Climate 21, 3282-3289.

    Abstract: “Satellite measurements from the Atmospheric Infrared Sounder (AIRS) in the upper troposphere over 4.5 yr are used to assess the covariation of upper-tropospheric humidity and temperature with surface temperatures, which can be used to constrain the upper-tropospheric moistening due to the water vapor feedback. Results are compared to simulations from a general circulation model, the NCAR Community Atmosphere Model (CAM), to see if the model can reproduce the variations. Results indicate that the upper troposphere maintains nearly constant relative humidity for observed perturbations to ocean surface temperatures over the observed period, with increases in temperature similar to 1.5 times the changes at the surface, and corresponding increases in water vapor ( specific humidity) of 10% -25% degrees C-1. Increases in water vapor are largest at pressures below 400 hPa, but they have a double peak structure. Simulations reproduce these changes quantitatively and qualitatively. Agreement is best when the model is sorted for satellite sampling thresholds. This indicates that the model reproduces the moistening associated with the observed upper-tropospheric water vapor feedback. The results are not qualitatively sensitive to model resolution or model physics.”

    Brogniez H and Pierrehumbert RT (2007) “Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data” Geophys. Res. Lett. 34, Article Number: L17812

    Abstract: “We make use of microwave measurements of the tropical free tropospheric relative humidity (FTH) to evaluate the extent to which the water vapor distribution in four general circulation models is faithful to reality. The comparison is performed in the tropics by sorting the FTH in dynamical regimes defined upon the 500 hPa vertical velocity. Because microwave radiation penetrates non-rainy and warm clouds, we are able to estimate the FTH over most of the dynamical regimes that characterize the tropics. The comparisons reveal that two models simulate a free troposphere drier than observed (< 10%), while the others agree with the observations. Despite some differences, the level of agreement is good enough to lend confidence in the representation of atmospheric moistening processes. A climate change scenario, tested on two models, shows a tendency to maintain the FTH to an almost fixed value be it an ascending or a subsiding regime” ',
  40. Well Chris, I say the agenda of the IPCC is to present data that the governments want them to present in order to make all their climate change policies work on the sheep we are. All i have seen from the IPCC is proof of the human contribution to climate change...why can't they put their heads together and stop giving everyone such a guilt trip. The IPCC's goal is to take the more attainable option and try and reduce our tiny contribution to global warming. It will make everyone a little bit happier but it sure isn't gonna change all the other contributing factors.
  41. That's a sad state of affairs Adamski. It's unfortunate when individuals are suckered into believing in conspiracy theories that benefit rather dubious agendas.

    Notice that the IPCC don't present proof of anything. The IPCC collates the scientific data on climate change. It presents evidence and assigns rough probabilities for causal relationships and future expectations.

    It would be interesting to known what what you consider "all the other contribution factors" to be. The evidence indicates that neither the sun, nor cosmic rays, nor tectonic activity nor ....well, I'm not sure what other factors there are, other than greenhouse enhancement, that can have contributed to the very marked warming of the last 100 years, especially the last 30-odd years. On the other hand the warming is rather similar to that expected from the massive enhancement of the earth's atmospheric greenhouse gas concentrations.

    It's not anything anyone needs to feel guilty about-it's really about addressing the problem with maturity and a bit of informed understanding. There are people and organizations that have an interest in maintaining a state of confusion about these issues....however it isn't too difficult to stay informed - a bit of skepticism about what one encounters on websites helps!

    It might be worth finding out a bit about the IPCC. The IPCC was set up explicitly to obtain periodic independent and authoritative acounts of current scientific knowledge free of the political factionalising that is especially a feature of the American sociopolitic. So the authors of the IPCC are nominated by national scientific organizations to ensure that that scientists (rather than politicians) assess and present the scientific data and evidence. The draft versions of the reports are posted on public websites so everyone can critique and make comments on the presentations (and the 10's of 1000's of comments are posted on the web, as are the responses to all of the comments by the authors).

    So the IPCC is very much a summary of the essentially uncontroversial science published in the scientific literature. If the IPCC does have a fault, it is that it tends to ignore the more extreme possibilities that result from, for example, dangerous feedbacks (like widescale methane release under strong greenhouse warming or rapid ice sheet disintegration which can't relaiably be modelled yet) which are real possibilities but as yet poorly quantifiable. So the IPCC reports are rather conservative.
  42. Sad but not necessarily untrue. I'm not believing someone else's theory Chris...for the record. That's my opinion. Also you cannot tell me that global warming isn't a conspiracy theory due to these people manipulating dubious facts and conspiring together while doing so...are you not in the same boat by believing this theory. I say 'other contributing factors' because there isn't a model yet produced by any climate change scientist that has predicted extremely accurately the speed at which global warming is occurring. They are always predicting a slower occurrence...that would mean that surely there are other unexplained factors in the issue. Look back in history and see what sort of state the Earth has gotten to and pulled through. During interglacial periods there was far less ice at the northern cap and sea levels were much higher...and not only that but most of the current species of both fauna and flora survived through these periods without mass extinction. In my above statements my goal has not been to slander the IPCC in any way but to try and put the point across that we as citizens are the final ears that receive information. There is an awful lot being done behind our backs.

    I will sum up with the fact that i believe any effort that can be made to suppress our contribution is a good idea. We are living far too luxuriously, using up vast amounts of energy in the manufacture of useless goods. But the reality is our contribution to global warming through the release of fossil fuel gases has a very limited time span. Is there an IPCC calculation on exactly how much carbon will be released when all of our deposits are burnt? They could work that out couldn't they? We are going to run out of stuff to burn and then there will most likely be a net reduction in CO2 in the atmosphere as it is sequestered. I'm studying Forest Science at Melbourne University and am aware of the biggest flaw in the current policies to deal with climate change...carbon counting. The concept is to make everyone in the population pay for their carbon output. What it doesn't consider is the carbon that is stored semi-permanently in sawn timber. The way it is described currently in the policies is that once a tree is cut down its carbon is released to the atmosphere. That's not right. There needs to be a consideration of all the timber that is used to build our houses, furniture not to mention the amount of carbon being sequestered in our gardens. Instead of bailing out those idiots in America they could've invested a huge amount into the development of forests. 700 Billion would've gone most of the way to creating a forest big enough to offset the majority of our emissions.

    Thank you.
  43. Hi,
    Not sure which 'argument' or thread on this site fits this best, but I wonder if anyone here can help explain away the arguments put forward by geologists like Segalstad (, on the balance between ocean & atmospheric carbon. I further read from same geologist that CO2 can remain in the atmosphere for about 5 to 10 years only, yet IPCC calculations rely on figures of 50-200 years. I'm no scientist but am convinced by weight of expert opinion about AGW, but am yet to find anything to refute the geolists claims, where so many other skeptic arguments are so easily debunked by comparison. Please help me to understand.
  44. Conspicously absent from consideration of what could have caused the warming for the 30 year period is ENSO and PDO. Here is a 58 year ENSO chart.

    Notice that prior to 1977 La Nina dominates the chart. After 1977 El Nino dominates the chart. The dominance of El Nino corresponds with the temperature rise of the last 30 years. Climate scientist Dr. Roy Spencer has calculated that up to 70% of the temperature rise that we have seen could be accounted for by ENSO and PDO patterns. There also seems to have been a flip in the PDO cycle in the last year or so that could well indicate another 20 years of flat or negative temperature trends.

    By the way, you may notice that the El Nino dominance in the chart was greatest from about 1977 to 1998. After that the distribution is a little more even. This corresponds well to the flatening of the temperature trend for the last decade. While that point is also challenged in this blog, I have proven it to be true in the relevant section.
  45. Re #43 Paul,

    I suspect that the "geologist" figure of 5-10 years relate to individual molecules of CO2 which are in continual exchange between the oceans/biosphere and the atmosphere. The relevant timescale when considering the effects of enhanced atmospheric CO2 levels is the timescale for the retention of high atmospheric CO2 levels once these are raised.

    For example, each year a massive amount of atmospheric CO2 is drawn down from the atmosphere into plants, especially during the Northern hemisphere growing season (Spring and early Summer), and then in the late Summer, and Autumn plant decay releases CO2 back into the atmosphere. If one were to be able to observe an individual CO2 molecule it would spend (according to the "geologist") 5 to 10 years in the atmosphere on average before being returned to the biosphere or oceans. However the nett atmospheric CO2 concentration doesn't much change on a yearly basis (during those periods when mankind is not pumping massive nett contributions into the atmosphere), since the exchange between the atmosphere and biosphere/oceans is near equilibrium (anthropogenic contributions aside!).
  46. Now THIS is interesting:
    Did Early Global Warming Divert A New Glacial Age?
    ScienceDaily (Dec. 18, 2008) — The common wisdom is that the invention of the steam engine and the advent of the coal-fueled industrial age marked the beginning of human influence on global climate.
    But gathering physical evidence, backed by powerful simulations on the world's most advanced computer climate models, is reshaping that view and lending strong support to the radical idea that human-induced climate change began not 200 years ago, but thousands of years ago with the onset of large-scale agriculture in Asia and extensive deforestation in Europe. ...
  47. And in follow up:

    "Nevle and Bird admit that volcanic activity and a decrease in the sun's intensity probably both played roles in triggering the Little Ice Age. Still, Bird said, human activity was undeniably important."
  48. saluki
    Dr. Spencer talks about this is a paper he tried to have published. The consensus refused to publish it. But you can find a link to it here in the PDO thread.
  49. Quietman, Saluki...that's exactly the thing that jumped at me before I heard of that paper. Also, even if C02 is contributing, which it may have/be, a lot has been shown that it's 'greenhouse' ability is a logarithmic function, and that it has already contributed as much as it can. Somehow that's left of the 'top 10' list at top/right. And who's the 'denier's when it's obviously a current cooling trend and the PDO has shifted? The fact that so many of the most shrill alarmist are calling for people to be treated like criminals and traitors for disagreeing really caps how outrageous this whole 'movement' has become. Basically, I've come to this conclusion: All previous climate changes are due to natural causes. C02 can't be proved to be the cause here, and natural causes can't be proved not to be, try as they might. Thus, it seems much more likely to be natural. I believed in AGW until I bothered to Google the phrase "scientific consensus". Almost immediately I figured out the debate was definitely not over. Therefore, Gore lied to me.
  50. This is an attempt to answer, for a skeptic (not denialist) friend, his proposition that since climate had changed before there was nothing to either explain or worry about. It is an attempt to distinguish between genuine skepticism and malign, planet-hating, denialism.

    The comment from tommybar "even if C02 is contributing, which it may have/be, a lot has been shown that it's 'greenhouse' ability is a logarithmic function, and that it has already contributed as much as it can" is interesting because it has suddenly started cropping up, in blogs around the world almost simultaneously. Could it be the latest talking point provided for the denialist anti-environment lobby? Funny how they all sing to the same tune (ice caps on Mars, Antarctic ice growing, planet now cooling) at the same time with each new attempt to stack the card deck, shuffle the pea, while distracting the punters.

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