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It's the sun
Climate's changed before
There is no consensus
Surface temp is unreliable
It's cooling
Models are unreliable
Ice age predicted in the 70s
Al Gore got it wrong
We're heading into an ice age
CO2 lags temperature
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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.

Volcanoes

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.

Summary 

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. 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:
    http://www.iceagenow.com/
    [ Response: Actually, I use iceagenow.com 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.

    http://members.iinet.net.au/~glrmc/2007%2005-03%20AusIMM%20corrected.pdf
  6. Will Nitschke (www.capitaloffice.com.au) 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":
    http://www.talkorigins.org/faqs/debating/globetrotters.html

    -- bi, http://zompower.tk/
  13. frankbi
    Re: http://www.talkorigins.org/faqs/debating/globetrotters.html

    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 http://www.middlebury.net:80/op-ed/pangburn.html.
  15. Dan Pangburn
    If your scientific claims in: -
    http://www.middlebury.net:80/op-ed/pangburn.html.
    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 http://www.ruralsoft.com.au/ClimateChange.doc 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: http://www.pbs.org/wgbh/nova/magnetic/timeline.html 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;
    http://www.pureenergysystems.com/news/2005/02/27/6900064_Magnet_Pole_Shift/
  28. Sorry, missed this one out: http://www.halexandria.org/dward761.htm

    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 migrators...eg 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...

    http://en.wikipedia.org/wiki/Solar_wind#Effect_on_the_Solar_System

    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.

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