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Could global warming be caused by natural cycles?

Posted on 11 January 2011 by climatesight

"What if global warming is just a natural cycle?" This argument is, perhaps, one of the most common raised by the average person, rather than someone who makes a career out of denying climate change. Cyclical variations in climate are well-known to the public; we all studied the ice ages in school. However, climate isn't inherently cyclical.

A common misunderstanding of the climate system characterizes it like a pendulum. The planet will warm up to "cancel out" a previous period of cooling, spurred by some internal equilibrium. This view of the climate is incorrect. Internal variability will move energy between the ocean and the atmosphere, causing short-term warming and cooling of the surface in events such as El Nino and La Nina, and longer-term changes when similar cycles operate on decadal scales. However, internal forces do not cause climate change. Appreciable changes in climate are the result of changes in the energy balance of the Earth, which requires "external" forcings, such as changes in solar output, albedo, and atmospheric greenhouse gases. These forcings can be cyclical, as they are in the ice ages, but they can come in different shapes entirely.

For this reason, "it's just a natural cycle" is a bit of a cop-out argument. The Earth doesn't warm up because it feels like it. It warms up because something forces it to. Scientists keep track of natural forcings, but the observed warming of the planet over the second half of the 20th century can only be explained by adding in anthropogenic radiative forcings, namely increases in greenhouse gases such as carbon dioxide. 

Of course, it's always possible that some natural cycle exists, unknown to scientists and their instruments, that is currently causing the planet to warm. There's always a chance that we could be totally wrong. This omnipresent fact of science is called irreducible uncertainty, because it can never be entirely eliminated. However, it's very unlikely that such a cycle exists.

Firstly, the hypothetical natural cycle would have to explain the observed "fingerprints" of greenhouse gas-induced warming. Even if, for the sake of argument, we were to discount the direct measurements showing an increased greenhouse effect, other lines of evidence point to anthropogenic causes. For example, the troposphere (the lowest part of the atmosphere) is warming, but the levels above, from the stratosphere up, are cooling, as less radiation is escaping out to space. This rules out cycles related to the Sun, as solar influences would warm the entire atmosphere in a uniform fashion. The only explanation that makes sense is greenhouse gases.

What about an internal cycle, perhaps from volcanoes or the ocean, that releases massive amounts of greenhouse gases? This wouldn't make sense either, not only because scientists keep track of volcanic and oceanic emissions of CO2 and know that they are small compared to anthropogenic emissions, but also because CO2 from fossil fuels has its own fingerprints. Its isotopic signature is depleted in the carbon-13 isotope, which explains why the atmospheric ratio of carbon-12 to carbon-13 has been going down as anthropogenic carbon dioxide goes up. Additionally, atmospheric oxygen (O2) is decreasing at the same rate that CO2 is increasing, because oxygen is consumed when fossil fuels combust.

A natural cycle that fits all these fingerprints is nearly unfathomable. However, that's not all the cycle would have to explain. It would also have to tell us why anthropogenic greenhouse gases are not having an effect. Either a century of basic physics and chemistry studying the radiative properties of greenhouse gases would have to be proven wrong, or the natural cycle would have to be unbelievably complex to prevent such dramatic anthropogenic emissions from warming the planet.

It is indeed possible that multidecadal climate variabilityespecially cycles originating in the Atlantic, could be contributing to recent warming, particularly in the Arctic. However, the amplitude of the cycles simply can't explain the observed temperature change. Internal variability has always been superimposed on top of global surface temperature trends, but the magnitude - as well as the fingerprints - of current warming clearly indicates that anthropogenic greenhouse gases are the dominant factor.

Despite all these lines of evidence, many known climatic cycles are often trumpeted to be the real cause, on the Internet and in the media. Many of these cycles have been debunked on Skeptical Science, and all of them either aren't in the warming phases, don't fit the fingerprints, or both.

For example, we are warming far too fast to be coming out of the last ice age, and the Milankovitch cycles that drive glaciation show that we should be, in fact, very slowly going into a new ice age (but anthropogenic warming is virtually certain to offset that influence).

The "1500-year cycle" that S. Fred Singer attributes warming to is, in fact, a change in distribution of thermal energy between the poles, not a net increase in global temperature, which is what we observe now.

The Little Ice Age following the Medieval Warm Period ended due to a slight increase in solar output (changes in both thermohaline circulation and volcanic activity also contributed), but that increase has since reversed, and global temperature and solar activity are now going in opposite directions. This also explains why the 11-year solar cycle could not be causing global warming.

ENSO (El Nino Southern Oscillation) and PDO (Pacific Decadal Oscillation) help to explain short-term variations, but have no long-term trend, warming or otherwise. Additionally, these cycles simply move thermal energy between the ocean and the atmosphere, and do not change the energy balance of the Earth.

As we can see, "it's just a natural cycle" isn't just a cop-out argument - it's something that scientists have considered, studied, and ruled out long before you and I even knew what global warming was.

Note: this is a guest post by Kate from Climate Sight, is also the Intermediate Rebuttal of the "It's a natural cycle" argument and happens to be our 140th rebuttal (it's actually ranked 84th by popularity but is the 140th to be added).

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Comments 1 to 50 out of 204:

  1. Great Job Kate!
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  2. "it's just a natural cycle" that happens to coincide precisely in timing and rate with the massive outpouring of CO2 over the last 150 years, and especially the last 30. The odds of the two things coinciding are astronomical (so to speak).
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  3. Perfect timing - see the same-day denier misinformation from here! (ideally now those ramblings should be debunked in a slightly more specific way).
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  4. Kate,

    "What if global warming is just a natural cycle?"

    To turn this question around I think the "average person" also struggle with the idea that it's just CO2.

    What are you talking about here? The last 150, 50 or 30 years?

    There is always the option that it isn't just anything, rather the combination of many things. Afterall the IPCC wording goes "that most of the warming observed over the last 50 years is attributable to human activities."

    The argument seems to be more nuanced than is it just natural or is it just anthropogenic but to what extent each is contributing to the present trend.
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  5. macwithoutfries

    The timing is great. Dismissing it as ramblings may play well with the gallery but I'm not sure it works well with the mindful "avarage person".
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  6. Excellent piece. The 'natural cycles' argument is the one that is usually inferred, if not directly evoked, every time skeptics mention the Vikings, the Medieval Warm Period etc. Climate changes 'naturally'; so it's nothing to worry about. Makes you want to pull your hair out ...!
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  7. I was quite struck reading Trenberth's 2009 paper, "An imperative for climate change planning: tracking Earth’s global energy".

    For example:

    "It is not a sufficient explanation to say that a cool year is due to natural variability. Similarly, common arguments of skeptics that the late 20th century warming is a recovery from the Little Ice Age or has other natural origins are inadequate as they do not provide the physical mechanisms involved. There must be a physical explanation, whether natural or anthropogenic."

    I recommend people read the whole paper because he points out that currently we can't actually total up the elements of the global heat budget to say why a given year is cooler or hotter.

    That's why this article seems like an over-simplification of the problem.

    As a relevant digression, I've read a lot of papers on the ice ages. There are lots of theories to do with Milankovitch cycles. But many Milankovitch theories cancel out many other Milankovitch theories because they are contradictory. Perhaps one is correct.

    To say we know and understand what causes temperature variations seems like something that needs demonstrating.

    I invite the writer to list the ocean heat changes for each year over the last 10 years and then match up the changes in albedo, OLR, ocean temperature with ocean heat content along with an explanation that links them together.

    Perhaps it is clear - I would really look forward to seeing the article.

    I did write an article some time ago about Trenberth's paper but from a different direction - Is climate more than weather? Is weather just noise?
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  8. It's well worth understanding what Bob Tisdale did in the post you link to macwithoutfries. He took a long time and a lot of figures to identify two small regions on the globe (one north and one south) on either side of the ENSO region, that most neatly encapsulate the progressive warming trend of his two larger regions. Once you subtract the progressive warming trend in both... surprise surprise the warming trend mostly disappears!

    The 'trick' he uses to 'hide the incline' is to pretend that the two smaller regions are oscillating in relation to some part of ENSO when in fact they are progressively warming with superimposed oscillations. He does not tell his reader why these two small regions show the warming trend. No real surprise that the overall anthropogenic warming with superimposed ENSO/La Nina-like oscillations happens to look a lot like the warming of the tropics and mid-latitudes, and so when you subtract one from another you end up with no trend. It is simply a cleverer way of doing the same thing McLean et al were guilty of last year.

    What we learn from Bob Tisdale: 1: The tropical oceans show a strong ENSO signature. 2: Subtropical/midlatitude oceans are dominantly progressively warming, with overlain pulses of heating/cooling influenced by heat originating from ENSO. Ah wait.. we knew that already. Do we learn what is causing the progressive warming (and of course the Arctic amplification)? Of course not! Do we learn how this fits in with other fingerprints of warming? Of course not...
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  9. A combination of what things, HumanityRules? I've yet to see any of the contrarians come up with a decent explanation of what-other than CO2-might be causing the last 60 years of warming (the period during which CO2 emissions rose at the fastest rate). Basic Physics tells us that CO2 molecules help to trap Infrared Radiation, & its this radiation that causes an overall warming of the planet. That's basic physics, HR, no matter how much you try & skirt around it.
    Also, if PDO & Incident Solar Radiation have both been trending downwards for the last 30 years, then why is that period of warming more rapid than the period of 1950-1980?
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  10. To those who offer the Singer/Avery "Unstoppable Global Warming: Every 1500 Years" arguments, you might ask whether, every 1500 years, the world's population discovers and exploits vast reserves of petroleum and whether, every 1500 years, that population reaches six billion.
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  11. My explanation of variations in warming is that variable natural factors amplify or delay warming. The warming from increased CO2 is steady but there are two primary natural factors involved: variable storage of heat in the ocean (correlates with ENSO pretty well) and variable amplification of warming (correlates with AO pretty well). The Erl Happ article at WUWT postulates AO levelling off and going negative. Whether it does remains to be seen, but a more negative AO will lead to less amplification and perhaps cooling if it continues.
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  12. @ScienceofDoom at 21:28 PM on 11 January, 2011:
    We know sea level is rising. While some of this comes from groundwater sources being discharged and some from glacial\ ice sheet melt, much\ most of it is from thermal expansion. This indicates to me the ocean is accumulating energy.

    If the oceans were losing energy to the atmosphere they would not be undergoing thermal expansion.

    We cannot answer all the questions yet, but we can put boundries on the uncertainties. Any hypothised mechanism must be within these boundries. If a natural cycle is part of the solution, where is the energy entering the atmosphere coming from?

    "That's why this article seems like an over-simplification of the problem." As it is only the intermediate answer I suspect the simplification is deliberate, though I would leave that answer ultimately to the author.
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  13. Philip64 at 19:58 PM on 11 January, 2011
    "Climate changes 'naturally'; so it's nothing to worry about."
    Forests burn naturaly, yet we still worry about human caused forest fires.
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  14. This 'it's a natural cycle' argument is one of my pet annoyances. Thanks for the post - it's clear and concise and should be obvious to all, but obviously some still have some trouble in understanding the basics.

    Now if someone said the rising temperature trend and other changes (eg ocean acidification etc) are 'a natural response' to all the CO2 waste we're dumping into the atmosphere, that would sit very well with me.

    @ skywatcher #9 - I suspected the Tisdale article was just another variation of McLean's 'I'll just remove the temperature increase to show there is no temperature increase' trick! I wasn't prepared to wade through the tortuous post in detail, but it looked that way when I skimmed it. Thanks for the confirmation.
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  15. Well done, Kate.
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  16. OT but don't know where else to ask. Is John Cook and family okay given the floods?

    My best wishes to all in Queensland. Our thoughts are with you.
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    Response: [John Cook] Thanks for asking. Although low lying parts of the next suburb are being evacuated, we seem to be okay where we are. Our area is a bit higher than surrounding regions which have flooded. So it's hard to imagine us being flooded. But then it's also hard to imagine an inland tsunami picking up houses with people inside them and carrying them across town which happened earlier this week. So we're keeping a careful eye on things.

    Appreciate your thoughts :-)
  17. Kate, excellent job! Thank you for this.

    Would it be possible to add a Figure? For example, below is Fig.3 from Swanson et al. (2009, PNAS). Solid, bold line = Observed GISS 21-year running mean global mean surface temperature; thin solid = quadratic fit to the observed 20th century global mean temperature; dashed line = that temperature cleaned of the internal signal.




    I'd like to highlight some key points that you make:

    "However, internal forces do not cause climate change. Appreciable changes in climate are the result of changes in the energy balance of the Earth, which requires "external" forcings, such as changes in solar output, albedo, and atmospheric greenhouse gases."

    And

    "However, the amplitude of the cycles simply can't explain the observed temperature change. Internal variability has always been superimposed on top of global surface temperature trends, but the magnitude....of current warming clearly indicates that anthropogenic greenhouse gases are the dominant factor."

    I highly recommend people read Swanson et al. (2009), who used an ensemble of 10 models (with coupled ocean-atmosphere dynamics) to study the long-term natural variability over the duration oft the global surface air temperature (GSAT) record. This is what they found:

    "Variability associated with these latter processes, generally referred to as natural long-term climate variability, arises primarily from changes in oceanic circulation. Here we present a technique that objectively identifies the component of inter-decadal global mean surface temperature attributable to natural long-term climate variability. Removal of that hidden variability from the actual observed global mean surface temperature record delineates the externally forced climate signal, which is monotonic, accelerating warming during the 20th century."

    And

    "The monotonic increase of the cleaned global temperature throughout the 20th century suggests increasing greenhouse gas forcing more-or-less consistently dominating sulfate aerosol forcing, although our technique cannot exclude other mechanisms not contained in the current generation of model forcing."

    So what we most likely have are warming and cooling cycles/oscillations from internal climate modes superimposed on a long-term, monotonically increasing warming from the increasing radiative forcing of GHGs.
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  18. Nice job, and this has the makings for a new entry in the argument list. Allow me to post a few more graphs from the zombie wars here:
    Temp vs. AO:
    AOtemp
    Temp vs. AMO:
    AMOtemp
    Temp vs. SOI:
    tempSOI
    Temp vs. TSI (since 1950):
    TSItemp
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  19. Just to be clear:
    AO = Arctic Oscillation
    AMO = Atlantic Decadal Oscillation
    SOI = Southern Oscillation Index (El Niño)
    TSI = Total Solar Irradiance
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  20. Keith, I don't really agree with your plotting there actually. It doesn't show the magnitude of the cycles. You should standardize them and put them on the same axis or something of the sort. You have to remember that 1 unit in one variable could be equal to 3 in another. Plus if you look closely at your temp/AMO graph you will see something very prominent... i.e. spikes in the AMO and temperature in 1878(eyeballing it) 1998 and 2010 which follow synchronously.

    Standardization can be done in excel with the standardize feature. use x-min/stdev
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  21. 21, Robert Way,

    I'm not sure what you think that "standardizing" (when measuring two different things with different units of measure there is no standard) would do, but based on your comment about AMO and temperature for 1878, 1998 and 2010, you do seem to have missed the point.

    Certainly any of these observations will have oscillations that match the details (shape) of the temperature line, but not the trend. It is very clear that there is an upward trend in temperature, and no such upward trend in any of the other variables. You can mix and match them all you want, and yes, you can come up with variations that match the details but never account for the warming.
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  22. "ENSO (El Nino Southern Oscillation) and PDO (Pacific Decadal Oscillation) help to explain short-term variations, but have no long-term trend, warming or otherwise. Additionally, these cycles simply move thermal energy between the ocean and the atmosphere, and do not change the energy balance of the Earth."

    Of course they don't do it by themselves. Think of the effect they cause though. When the PDO goes negative for a time more ice and snow build over the N hemisphere. What happens then? More energy is reflected away; Less water vapor is in the air. (That forgotten greenhouse gas that we still can't properly quantify worldwide, either presently or historically)

    I still think we are in a warming cycle. Sure Milanovich is important, but there is a heck of a lot of variability in when the ice ages trip into motion within that cycle. When it does it is sudden. In fact Milanovich may just be coincidental rather than causative when it comes to Ice Ages. No one has ever come out and proven Milanovich causes the Ice Age cycle.

    I think it is all about when sea levels rise high enough to really upset the important ocean circulations that allow us to stay warm. Until then, we will probably have basically neutral periods followed by warming periods, unless some big old volcano blows up. Then we could get some major cooling.

    JMO, but there are good reasons to think this way.
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    Moderator Response: [Daniel Bailey] See my response to you at comment 25 below.
  23. Sphaerica,

    I certainly understand the point of the post and I am just as much an AGW proponent as the next person. I just didn't think it was the appropriate way to graph those items because it makes clear synchronous behavior not be so apparent. The same can be said of divergences. Putting them on a similar scale which considers their standard deviation is probably the best manner or putting dual axis.

    I acknowledge that cycles are not necessarily causing the trend but I think it is important to acknowledge that some cycles contribute to it at times and hide it at times.
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  24. Re: cruzn246 (23)
    "When the PDO goes negative for a time more ice and snow build over the N hemisphere."
    Apparently you didn't read the post: PDO has NO long-term trend. Strike one.
    "That forgotten greenhouse gas that we still can't properly quantify worldwide, either presently or historically"
    Oh-so wrong. Very well studied, quantified and understood. Strike two.
    "unless some big old volcano blows up. Then we could get some major cooling"
    Anthopogenic-derived CO2 releases amount to 100X that of all of the world's volcanoes combined. Humans breath out 10X as much CO2 as those selfsame volcanoes do (but that human CO2 is part of the closed carbon cycle, unlike fossil fuel CO2). Anyway, volcanic cooling imposed on the globe is transient, unlike the documented effects of CO2. That's strike three, you're out. Next batter...

    (BTW, it's "Milankovitch")

    The Yooper
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  25. Daniel @25,

    Quite remarkably, cruzn246 somehow just managed to get an edge and caught behind, get bowled and then stumped ;) Everyone on the pitch is aghast...
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  26. #22: "variations that match the details but never account for the warming."

    Sphaerica speaks wisely. Anyone who thinks it's just a natural cycle should be asked to explain this graph from an MWP thread:



    There is nothing natural about what happened in the last 100 years. Natural excursions prior to the last century have neither the magnitude nor the rate of change. Those natural cycles are just noise in the presence of the recent trend.

    No amount of skeptical handwaving can make the contrast between recent temperatures and the 'natural cycles' go away.

    Yooper (#25), I believe the expression is 'Well bowled, Sir!' Perhaps Albatross can let us Yanks know how to be so polite.
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  27. My favorite sports broadcaster was Ernie Harwell from the Detroit Tigers. His favorite saying after a strike three call was "the batter just stood there like a house on the side of the road!"

    Skeptics think they have good reasons to believe in anything other than the science, but that leaves them unable to turn on the high fastball up in the zone and unable to hold up on the curveball in the dirt.

    Reminds me of this quote.

    The Yooper
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  28. Keithpickering @ 18... Wow. Is there a way to link to those graphs?
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    Moderator Response: [Daniel Bailey] Rob, if Keith doesn't mind hosting them, you can just right-click on the desired graphic, select "view image" and then the URL of just the graphic will show in the location pane.
  29. RE: Cyclic Climate Changes: What the Russians Say.

    The English translation of "Cyclic Climate Changes and Fish Productivity by L.B. Klyashtorin and A.A. Lyubushin can be downloaded for free thru this link:

    http://alexeylyubushin.narod.ru/Climate_Changes__and_Fish_Productivity.pdf?

    NB: This mongraph is 224 pages.

    By analyzing a number of time series of data related to climate, they found that the earth has global climate cycles of 50-70 years with an average of about 60 years with cool and warm phases of 30 years each. They summerize most of the studies that show how this cycle influences fish catches in the major fisheries.

    The last warm phase began in ca 1970-75 (aka the Great Shift) and ended in ca 2000. The global warming from ca 1975 is due in part to this warm phase. A cool phase has started and they predict it should last about 30 years.

    Several others studies have found this 60 year cycle. During the cool phase La Nina years usually out number El Nino years as was the case from ca 1940-70.

    KP @ #18

    The 60 year cycle can be seen in the middle figure: 1850-1910 and 1910-70. However note that after 1970-75, the temperature did not decrease as it did at about 1940. Presumably this is due to extra heating caused by CO2 whose concentation began to increase at a greater rate than before that time.

    There is one other factor that contributes to global warming: Fine black dust from rubber and asphalt.

    I ask this simple question: Since 1900, where have the many billions (and billions and billions...!) of pounds of rubber and asphlate dust gone?

    The short simple answer is anywhere and everywhere. Synthetic rubber does not degrade upon exposure to sunlight, oxygen or microbes.

    A passenger car tire with an A treadware rating will lose about a pound of rubber over it lifetime. Can you imagine how much rubber 18 wheelers shed on the highways?
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  30. Daniel.... Um... Right click?


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  31. Heehee... Daniel. I actually know the command (option+click). Just wanted to inject some humor. ;-)
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    Moderator Response: [Daniel Bailey] Sorry, Rob. I'm so completely mouse-dependent I could not use my laptop without one.
  32. Re: cruzn246 (23)
    "When the PDO goes negative for a time more ice and snow build over the N hemisphere."
    Apparently you didn't read the post: PDO has NO long-term trend. Strike one.
    "That forgotten greenhouse gas that we still can't properly quantify worldwide, either presently or historically"
    Oh-so wrong. Very well studied, quantified and understood.

    Really? Tell me in PPM, like they do with CO2, how much water vapor is in the earth's atmosphere today. Then tell me how much was in the atmosphere in 1800.

    We just went through a summer with record high lows for most of July and August. We also had record high dewpoints, on average, over that period. H2O plays a huge role in a warming cycle that is very overlooked.

    Strike two.
    "unless some big old volcano blows up. Then we could get some major cooling"
    Anthopogenic-derived CO2 releases amount to 100X that of all of the world's volcanoes combined. Humans breath out 10X as much CO2 as those selfsame volcanoes do (but that human CO2 is part of the closed carbon cycle, unlike fossil fuel CO2). Anyway, volcanic cooling imposed on the globe is transient, unlike the documented effects of CO2. That's strike three, you're out. Next batter...

    (BTW, it's "Milankovitch")

    The Yooper

    Yeah, it is Milankovich. Dan, I'm not talking about your run of the mill explosions of volcanoes. I'm talking about the ones that truly alter climate, like Tambora or Mount Pinatubo.
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    Moderator Response: [Daniel Bailey] Please read this post by Tamino. He proves the transient cooling of volcanoes by removing their effects and that of cyclical stuff (like El Nino) to get this (as you can see, no lasting presence of Pinatubo):
  33. 30, 31, Rob Honeycutt,

    How to right click with a Mac trackpad (without using the dang control key).
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  34. Thanks Sphaerica! I just got this new track pad so I'm still learning it. That's a great tip.

    Sorry for the OT comments.
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  35. Cruzn46,

    "Really? Tell me in PPM, like they do with CO2, how much water vapor is in the earth's atmosphere today. Then tell me how much was in the atmosphere in 1800."

    This is off topic. But how about you do calculations? And absolute WV content is measured in g/kg either as specific humidity or as mixing ratio (r). We know that mean RH is ~70%, and we know that the saturation vapor pressure (es) is determined by temperature alone. Between the equations for r and es and RH, and with knowledge of the mean global SAT (and applying) the assumption for constant global RH of 70% you could probably get an estimate of the mixing ratio circa 1880. It would be an interesting exercise, but completely unrelated to this post.

    Trenberth et al. (2005) found that from 1988 to 2003 the global precipitable water vapour (PWV; vertical integral of r though the atmospheric column) content increased by about 1.3% per decade over the oceans, and that this increase was in turn because of an increase in air temperature, with about a 9% increase in PWV per Kelvin, again over the global oceans.

    Results form that paper also offer a clue as to the value of mean r circa 1880. But again the answer would be off topic.
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    Moderator Response: If anyone insists on pursuing this topic further, they should do so on a thread revealed by typing "water vapor" into the Search field at the top left of the page.
  36. Thanks for the suggestions re: images - I am on the lookout for something to visually break up the page and enhance understanding.
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  37. #20 Robert Way:
    I quite agree, and I'm in the process of redoing all these graphs with explicit y-scales. See my post from a few days ago, "Graphs from the Zombie Wars" for an example.

    #28 Rob Honeycutt
    Please use these any way they might be useful -- if you can get that right-click thing working.

    #29 H Pierce
    Yes indeed. One needs to remember that AMO and PDO are temperature indices, i.e., they are detrended subsets of the global temperature dataset. Therefore one expects to see short-term correlations. It's the long-term trend that's the issue.
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  38. #18 keithpickering and #21 Sphaerica, I never figured trend was relevant in those variables (AO, etc). The relationship of those to global average temperature is not linear, and the variables themselves are somewhat cyclical (not linear). However, the AO to amplification link that I talked about doesn't seem to be evident. AMO being oceanic rather than atmospheric looks a little more promising. I am only trying to explain fluctuations in the rate of global temperature increase to help determine the factors that control amplification of warming from CO2 or ocean storage of CO2 warming, both of which fluctuate.
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  39. From a basic systems perspective, a system's response to a perturbation can either be underdamped, in which case the system rapidly changes, overshoots and oscillates to a new equillibrium. Or, it can be overdamped, in which case it more slowly and monotonically drifts to a new equillibrium. Is there any evidence whether climate response to CO2 behaves in either of these fashions?
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  40. #18, h pierce

    Sorry, you are wrong about rubber. It does degrade, though it does take a while. Sunlight is pretty vicious to rubber and plastic, and rubber eventually degrades because of the initiators used in its synthesis.
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  41. 39, BKsea,

    Off the top of my head, from what I observe and understand, the answer is "both." That is, the ocean is a vast heat/CO2 sink, so it is damping both the warming and the growth of CO2 in the atmosphere.

    On the other hand, from what we've seen of past events, such as the termination of interglacial periods and other events, there can be spikes when certain tipping points are reached. These don't need to be the same "tipping points" people think of in relation to runaway warming... just points where "slow-and-steady" abruptly transitions to "oh-shi*".

    But right now I'd say "more slowly and monotonically drifts" is the better description, with the understanding that that same damping will apply to trying to slow things down now that they've started. That is, even if we stopped all CO2 emissions right now, that "slowly and monotonically drifts" would continue for a very, very long while.
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  42. Muoncounters (graph #28 as things are now counted) shows roughly .8C of warming since the zero mark (whatever that is for that graph). It just raised the question in my mind - how many BTUs does it take to raise the temperature of Earth by .1C? This number might be a fun one to help people grasp the magnitude of such a tiny change. Every rock, every house, every leaf, every river, etc. .1C hotter than it was - all at once.
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  43. BKSea,
    I don't know of any researcher willing to go out on that limb. But, I don't know all. It's a pretty thin branch no matter which side you believe.

    However, the same question has come to my mind more than once. Looking at ice core data, there appear to be upper and lower limits to "natural" perturbations. At times, there appear to be plateaus of relative stability at the top and bottom of these limits, with rapid changes between them. However, there is also a PETM event which is outside of these limits, as well as broad expanses of geologic time where the temperature has been outside of the recent glacial band.

    My two cents: We are off the map. There has never been a time like the one we are in the process of creating in terms of layout of the continents, amount of C sequestered in clathrates and permafrost, rate of climate forcing introduced, etc. We can't just can't tell whether the change will be smooth or abrupt. Looking at the forces and feedbacks involved, there's nothing that acts linearly; so, my out-on-a-limb guess is that there will be an abrupt tipping point. Heck, from a geologic time-scale perspective, the recent change in progress would look like some abrupt discontinuity on the graph.

    Actually,
    I think the number would be a) too big to be meaningful, and b) depend a lot on how deep you wanted to go in the ocean and land; atmosphere, not so much. I once did a back-of-the-napkin estimate of just the latent heat difference in the loss of Arctic ice. It was huge, and that is just a fraction of the change in heat content of oceans.
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  44. I am a climatologist by hobby mainly because I study and occasionally chase hurricanes. I can use the most basic aspect of science and demonstrate why earth won't become venus.


    Look at the periodic table. Air is a solution (meaning no molecular bonds) of roughly 3/4 nitrogen and 1/4 oxygen and trace gasses (21%?). When an atom bonds to others to become molecules, the atomic weight combines. When air becomes saturated...when the total atomic weight of water in a given point of the atmosphere grows higher than the total atomic weight of the air that is holding it up, it falls down as rain, snow, dew, etc. Now, Carbon Dioxide has a much heavier atomic weight than air or water vapor. Thus when CO2 gets ejected into the atmosphere, it falls harmlessly to earth where the trees use it for food. To this day, the military uses CO2 as fire suppression on the lower levels of ships (engineering areas) because it naturally sinks in air.

    Because of CO2's heavier atomic weight, barometric pressure (the weight of the atmosphere on the earth) has not increased at all in the last 150 years. If CO2 were building as they say, the barometric pressure would have increased .5mb at sea level in the last century. That has not happened. The cyclical shift In ocean currents and temperatures gradually went from cool to warm in the '30s and again in the early '80's. this cycle starts in Pacific lags a decade or so in the Atlantic (PDO and AMO respectively). When the Pacific warmed, so did the land next to it then the Atlantic followed. The result was honest scientists seeing actual global warming. Now the pacific ocean is back in it's cold phase and scientists are trying to hide the resulting temperature drop. In the next 5 years the Atlantic will go cold too.

    The pacific went cold extremely early this time. The only time this can be archaeologically proven to have happened before was in the 13th century when archaeological evidence shows a likelihood of the Northwest Passage being open briefly at the very end Medieval Warm period which peaked drastically then ended suddenly at the end of the 13th and 1st half of the 14th century. To see what followed, google "little ice age". It seems plausible that the opening of the "Northwest Passage" flooded the Atlantic Ocean with cold dense fresh water blocking the Gulf Stream which moderates temperatures along the Americas, West Indies, Europe and even it even impacts Africa as the cold "Canary Current".

    The sudden drop in temps along the eastern US and Eur-Asia was preceded by a decade or so of slow global cooling and extreme weather in Europe resulting in crop failures, just like the cooling that has been happening since 1998. The last "little ice age" killed half the population of Europe due to starvation and plague. Is it possible that all the crop failures in the news lately are simply history repeating itself? No, and neither are the plunging temperatures, record snows in areas that haven't seen such things since the 1700's which was the peak of the last "little ice age". I have already heard some folks in the weather watching community comparing this winter to the winter Washington and the American Revolutionary Army spent at Valley Forge.
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    Moderator Response: [Daniel Bailey] Welcome to Skeptical Science. First rule to observe here is to abide by the Comments Policy. That means NO accusations of fraud or dishonesty, among other things. Even by intimation. Your comment hangs precariously across that line. Future comments of this nature will be summarily deleted. As to the scientific content of your comment, for someone studying climate science there is so much in error. Please follow the advice and direction JMurphy expressed so well in comment number 47 below. Your compliance is appreciated, as is substantive dialogue. Thanks!
  45. 13MPG, this has to be the most grotesque conflation of nonsense and misinformation I have ever seen. Thanks for the laugh.
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  46. 13MPG
    building new theories from a measured event is a nice intellectual exercize. But before claiming its validity you need to confront it with reality.
    There are several troubling claims in your comment, starting from the sinking of CO2, the flooding (sic) of the Atlantic Ocean, the cooling from 1998 and the halving of the european population in the 17th-18th century during the so-called little ice age. Your theory does not stand even the most trivial sanity check.
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  47. 13MPG, before your first post, you should have read Beginners Start Here, The Big Picture, and Most Used Skeptic Arguments.

    If you had read all that first, your post would have had very little left that hadn't been already looked at, discussed and countered.
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  48. 13MPG, I second the start here recommendation. The only argument of yours that I haven't previously read here was the atmospheric pressure increase. This paper http://dx.doi.org/10.1016/j.energy.2010.07.017 says that "a crepuscular atmosphere having a carbon dioxide content of 683 ppm, ... a pressure of 1.021 bar,..." so that argument is wrong too.
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  49. 13MPG

    Read this document (The Absence of Stratification and Rapidity of Mixing of Carbon Dioxide in Air Samples) from the Journal of Biological Chemistry (1927), about the diffusion of CO2 in air, in particular the summary:

    http://www.jbc.org/content/73/2/379.full.pdf

    The point is that if you were correct about CO2, then we would be detecting stratification of gases in the atmosphere and we would all be CO2 breathing creatures, not air/oxygen breathing creatures.
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  50. #40 Chemware

    Modern synthetic rubber contains anti-oxidants and UV protectants, and it does not degraded to any appreciable extent when exposed to air, sunlight, and microbes.

    I have used tires that are over 20 years old and they haven't changed much at all in physical appearance. And there is no mold or moss growing on them.
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