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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 101 to 150 out of 204:

  1. #100: "follow the scientific method..." I wonder if you would care to apply your own practice and examine your statement in #67, 'Of course its natural.' Particularly in the context of this post: --it's always possible that some natural cycle exists, unknown to scientists and their instruments, that is currently causing the planet to warm. --the hypothetical natural cycle would have to explain the observed "fingerprints" of greenhouse gas-induced warming, along with the arguments against 'natural cycles' in the following paragraphs.
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  2. @ 100 Pirate, Seriously, i would think it should be the other way around. High school teachers should consider their 'beliefs' when they realize the leading scientists of the world have thoroughly examined and tested all possibilities and have determined CO2 is the cause of rising temperatures.
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  3. Pirate: I'm worried that you're misrepresenting AGW to your students because you don't understand the theory. How do you present the radiative physics of CO2 and CH4 to your students? What other sides are they shown? I wasn't aware that there was an "other side"--a comprehensive alternative theory to AGW that explains the instrumental and proxy data.
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  4. apirate: The fact that there are science educated, experienced teachers (college and high school) who do not believe in the AGW theory, should cause you to at least consider their position. We have considered it, and rejected it for very good reasons, as a perusal of the "skeptical arguments" at the upper left will reveal. As this article says, "'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." There are also "science educated, experienced teachers (college and high school)" who argue for young-earth creationism, AIDS denialism, racialist interpretations of IQ data, and God only knows what else. To "consider their position" requires considering their position vis a vis peer-reviewed science and the evidence that supports it. Such consideration leads me naturally to the conclusion that these people are overwhelmingly likely to be cranks. And on at least some of these issues, I would hope that it leads you to that conclusion, as well. One thing "skeptics" need to explain, IMO, is why they tend to hold climate scientists to a completely different standard than other scientists.
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  5. "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)." Regarding the statement above: It cannot be scientifically stated that "we are warming far too fast to be coming out of the last ice age." To say that, one has to have something to compare it to for it be called abnormal. We have historical temperature data that is fairly well accepted by all scientists going back hundreds of thousands of years as presented here . Any graphs generated from this data clearly show a cyclical, sharp rise in temperature followed by a more gradual lessening of temperature. Plus, the Earth is not warming rapidly. The temperature appears to be leveling off, if not dropping as referenced here . Even taking Mann's Hockey Stick Graph at face value, it becomes a matter of choosing timescales to demonstrate any appreciable warming. I could go on, but let me stop here and ask a question. Can you at least understand how intelligent, educated people from around the world can question the theory of human-induced global climate change?
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    Moderator Response: [Daniel Bailey] I'm sorry, but I cannot let you go on. #1, there is no recent leveling off in the rise in global temperatures, as shown here (ENSO and transient volcanic warming removed): #2, as far as ice core records, we clearly understand that the forces in operation during previous ice age cycles are not in play today, as summarized here: Can you at least understand how intelligent, educated people from around the world can question your non-science-based denial of the theory of human-induced global climate change?
  6. apiratelooksat50 - "Can you at least understand how intelligent, educated people from around the world can question the theory of human-induced global climate change?" Yes, I can. However, I would have to qualify that as "Unfortunately, yes, I can". One of my principles is that regardless of whether or not I agree with any particular idea or position, it's important to respect why that person holds that position. Strongly felt opinions are tied to strong personal reasons, for better or worse. But - I'm not pro-AGW (as you asked earlier), I'm pro-reality. I really really really wish AGW was not the case, but all of the evidence appears to point that way. I constantly hope for someone to prove that it's a cycle, or an error in measurement, or whatever - and I'm constantly disappointed. Temperatures are going up, cherry-picking the last 4-10 years notwithstanding. CO2 levels are above any seen in the last half million years! And the change in temperature is faster than anything in the temperature records. If you disagree - provide the evidence.
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  7. Please consider the timescales, historical changes occured over millenia while the current change is occuring over decades. Questioning is the basis of learning. Refusing to acknowledge the multiple, independent lines of empirical evidence on the basis of preconceived notions is not productive (to put it politely). As for "temperatures are leveling off if not dropping", please refer to argument #4.
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  8. Pirate, the paper you referenced is from 2002. That makes it almost a decade old. Can you understand how ludicrous it is to cite it as evidence that "the temperature appears to be leveling off, if not dropping"? You are not helping your credibility.
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  9. #105: "temperature appears to be leveling off" So much for the scientific method, which requires data to substantiate any hypothesis. Hypothesis: temperatures leveling off Data: the latest announcement of temperatures for 2010. Analysis: Data conflicts with results predicted by hypothesis Conclusion: Hypothesis invalid "it becomes a matter of choosing timescales to demonstrate any appreciable warming." Again, see the graph here. No choice of timescale necessary. What is your hypothesis for what makes the right-hand end of that graph so different from the rest?
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  10. 100, apiratelooksat50,
    ...should cause you to at least consider their position.
    I don't consider anyone's "position." I look at facts and explanations, I study until I thoroughly understand, and then I either arrive at a conclusion (in agreement or at odds with any particular source), or else I "shelve" it in my head and wait for more information. I spent many years as a "true skeptic," in that I did not know what to believe, and so I researched each and every argument I saw, taking them each at face value. After many years of this, I began to become more and more comfortable with almost all of the information and arguments, from paleoclimate to physical and atmospheric chemistry to statistics to feedbacks and ice ages and so on. It's been enlightening, and fun, and a valuable experience. But at the very end of that long road, I found that 99.999% of the arguments against AGW are in fact smoke and mirrors. I began to be embarrassed at some of my own past doubts, and I began to look very, very carefully at any and every new magic nail that skeptics tried to hammer into the AGW coffin. Now, I barely flinch when I see the latest paper by Lindzen and Choi, or Miskolczi (lol), or the latest proclamation from anywhere. I'll eagerly read it, if I can, just for fun, just as a test to see if I can see the inevitable glaring faults. And if I fail, I just wait for those who are more experienced (and have more time) to do it. But it always, always turns out that way. But at the end of the day, my own "position" is entirely one of understanding, and I have no doubts whatsoever about almost all of the issues. This is what concerns me, because in this thread and others, you seem to present the same long (almost unending) laundry list of ill-founded doubts that float around the Internet that I now smile at (condescendingly). If your own doubts were limited to just a few of these, that would be one thing. That you repeat so many clearly fallacious arguments, and will not alter your position when presented with clear and concise discussions of facts, is concerning. I'm not putting you down. On the contrary, I'm merely trying to point out that you have come across as a closed minded individual, who is easily swayed by close-but-not-quite scientific arguments. If you are a science teacher, that is unacceptable. You must hold yourself to a higher standard. You should become a true skeptic. You should treat everyone and everything with sincere doubt, and learn until you feel you truly understand. Your level of understanding now is not adequate for a science teacher.
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  11. apirate I am not sure what you mean that a teachers position on a subject should be considered?? Is science about democracy?? Your story IMO doesn't add up.
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  12. @yooper: "Commenters on "both sides" of debate get moderated on SkS. " I can attest to this. I have often been moderated for being to harsh in my responses to den...er, I mean, "skeptics." @pireate: You are not being singled out because of your opinion. You are being moderated because your comments are found to violate the site's policy. Take it in stride, just like the rest of us. "I believe for the most part most researchers are honest people and most likely gravitate to schools or institutions that support their beliefs and findings." That's utterly ridiculous. Good schools don't "support the beliefs" of scientists, because science isn't about belief or opinion in the first place. That kind of thinking belies your considerable bias on this subject. "The fact that there are science educated, experienced teachers (college and high school) who do not believe in the AGW theory, should cause you to at least consider their position." Not really, because their position is *always* based on the same faulty science we've been debunking for years. Simply put, contrarians have yet to come with a *single* valid argument against AGW. If you're going to go with Argument from Popularity, you should consider that 97% of publishing climate scientists support AGW theory. I'd argue you're basically saying that only 3% of climate scientists are both onest and competent. That's an extraordinary accusation, and one made without evidence. How is that not smearing the good names of thousands of hard-working scientists?
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  13. #112: "science educated, experienced teachers (college and high school) who do not believe in the AGW theory" Perhaps Mr. Pirate could recommend SkS to some of his colleagues. Good educators -- especially in the sciences -- are expected to be 'life-long learners' and there's plenty to learn from right here.
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  14. Re: apiratelooksat50 (105) Please see my in-line response to you in your comment at 105 above. Thank you. The Yooper
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  15. "Stratospheric temperature decreased after each volcanic eruption and then very slowly growing." I'm sorry, but this claim is factually *incorrect*. Volcanic Eruptions actually *warm* the stratosphere-not cool it-as the graph you link to clearly shows. Yet in spite of several major warming spikes, caused by major volcanic eruptions, there is a clear cooling trend in the stratosphere. Indeed, this cooling trend is almost a mirror image of the warming trend in the troposphere. Now what *natural* phenomenon can you think of that can consecutively warm the troposphere & cool the stratosphere? I certainly can't think of any-but I know of one man-made phenomenon which can.
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  16. Only KR attempted to answer my question. I am going to ask again. Refer to the chart the Moderator inserted at #105. Certainly, CO2 is spiking. Temperature has spiked for this cycle, and depending on the timeframe you analyze is either rising, holding steady or falling. Without debating what is happening now, or in the past 10 years, 30 years, 100 years, or whatever time period with temperature: Given the chart: Can you understand (not agree!) how intelligent, educated people around the world can question the theory of human induced climate change? Forget about anything else I've ever written, hinted at, been disagreed with, or been misunderstood about. And, just answer that question.
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    Moderator Response: [Daniel Bailey] As an educator, surely you can appreciate one of your students trying to over-simplify something which is irreducibly complex. That is what you are doing. The temperature rise of the past 30 years is unparalleled in the paleo record. Over 100 years of hard-won knowledge of atmospheric physics and empirically-measured factors all point to the same explanation: the rise in CO2 (which is anthropogenically derived) is acting as a forcing to temps, driving them upwards (and will continue to do so beyond our lifetimes). Intelligent, educated people around the world (even educators) understand this. How is it you do not? You are failing this test.
  17. Muon @113 I actually have forwarded your website to my colleagues along with other websites. I've even linked to them on my school website and my Facebook page. I stress to my students to examine all sides and make up their own minds. That's why I love science. There is always something to learn!
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  18. apiratelooksat50 "Given the chart: Can you understand (not agree!) how intelligent, educated people around the world can question the theory of human induced climate change?" No, I can't. If you're going to question the theory, then you need to have a firm, scientific basis for doing so-yet you've failed to provide any basis beyond a strongly held belief. Look again at figures A & B at #105. The warming caused by the Milankovitch cycles occurred over *thousands* of years-equating to an average warming rate of less than +0.02 degrees per decade. The warming which has occurred since 1950 has been at a rate of +0.12 degrees per decade-with no sign of it leveling off. Since 1980, the warming rate has been +0.16 degrees per decade-suggesting that the warming trend is *accelerating*. This is in spite of the fact that the PDO has been trending downwards, & Total Solar Irradiance has fallen at a rate of 0.02 Watts/Meter Squared over that same time period. Not only that, but every *natural* source of warming should be warming the *entire* atmosphere fairly equally. Yet what we're seeing is a warming of the troposphere, but a cooling of the stratosphere-consistent with heat being trapped in the lower atmosphere & failing to get out to space. When you can provide a rational, scientific explanation for these phenomena, I'll be more than happy to listen to them, but so far you've failed to provide any. You learning anything yet?
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  19. #117: Thanks, but SkS is not my website; I'm just a passenger on this bus. But I look forward to their questions and/or input. #116: What I cannot understand is how a scientifically or mathematically literate person can look at the GISS graph in #105 and not be struck that something very unusual is happening. Said literate person would then begin researching context (perhaps here), look for consistent explanations (and as I believe many have done), find a wealth of evidence that points to AGW or ACC or whatever we are calling it now. The literate person will weigh the evidence and consider the opinions of those with more experience in the field. In that process, the arguments of the so-called skeptics, particularly their reliance on unknown 'natural cycles' will come up short. You say 'given the chart'; I say the GISS graph is just one link in a long chain that must be followed to its logical conclusion. It's not easy, but it is an interesting and very important puzzle.
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  20. There is always something to learn! The effect of volcanic eruptions on the stratosphere, for instance. And the pointlessness of citing a decade-old opinion piece as "evidence" of cooling.
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  21. apiratelooksat50 - "Can you understand (not agree!) how intelligent, educated people around the world can question the theory of human induced climate change?" Yes, apiratelooksat50, but I cannot agree with them. In one word, "rates". We're warming at 5-6 times the fastest rate ever seen in the historic record, without any of the forcings (orbital inclination, solar variance) that have induced those changes. The only thing that matches current warming is CO2. When I state that I understand why people might not agree, I'm referring to any number of reasons - the feeling that we can't be affecting the globe, anthropocentric "the world was made for us" views, reluctance to change, the "get dem darn revenuers outta my back yard" resistance to large scale social interaction, any number of things. Reasons that I do not consider rational. Strong, yes, rational, no. Given the chart, and an unbiased reading of it, I can only conclude that we've f&%$@^d things up, and we're changing the climate. I don't understand how any other conclusion could be reached unless biased by preconceptions.
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  22. Apirate@116 - I can understand why thinking people doubt - until they examine the evidence! I started out "believing" in AGW - after all, scientists who dedicated their careers and lives to this research (for little pay - even now) had come to this conclusion - no upside for them. Then I began to see all the doubt, and I went to sites like The Air Vent and the Blackboard. These are sites were VERY smart people try to pick apart climate theory. I noticed that they focused on one world government, that they thought cap and trade was a bad idea. But when they focused on the science - they tended to support, or find that, using their analysis, warming was misstated by climate scientists by a few percentages (remember the Urban Heat Island issue? they tried to prove that UHI was inflating the data at the Blackboard - they instead found that climate scientists UNDERstated warming by a tenth of a degree or so, because they were too vigilant in correcting urban-influenced sites. So I then began to critically examine the arguments, and I found skeptic arguments, with the possible exception of the missing ocean data, were provably false. So I now know AGW is the correct theory (within the limits of scientific understanding) I have answered your question cheerfully - will you do one favor for me? Express as clearly as you can your strongest reason for doubting climate science (I say climate science because most people don't realize that AGW=climate science - if you understand climate science then you are an "AGW believer"; "pro-AGW" (your term); and you understand AGW.). Once you state it, read the responses you get here (and the explanations provided in the skeptic arguments section, and honor us with either a "I know understand this element and agree with the climate scientists" OR "I still don't agree because X." And then repeat this holistic process with each of your arguments. Most skeptics get to the point of stating their argument, but then they never process it and either state why it explained the matter to their satisfaction, or what information they need to satisfy themselves. It is a complicated issue - but I think anyone (such as myself even) who is not willing to accept what the highly trained professionals tell us at face value is responsible for understanding it on their own. It seems weird to not accept the scientific evidence, but not have nay other theory to support in its stead (I am ruling out denial as a scientific theory...)
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  23. Putting aside whether apirate's interpretation of the graph is defensible, I think his question is somewhat silly. "Intelligent and educated" people routinely believe bizarre things on the basis of little or no evidence. What people need, generally speaking, is a self-reflexive stance that allows them some critical distance from their ego, political assumptions and so forth. Without that stance, and the humility that tends to accompany it, intelligent and educated people are as prone as anyone to make fools of themselves. Maybe more so. An educated and intelligent person might well look at this chart and doubt AGW. But a really intelligent, really educated person would then go on to consider whether it's plausible that thousands of scientists who have drawn the opposite conclusion are misreading the chart. That kind of self-questioning is what tends to be missing from the "skeptical" outlook, in my experience. Particularly when assessing a field that's not your own, the truly intelligent and educated approach is to assume that the experts in that field know a lot more about it than you do. And that if you propose to challenge them on their own turf, you need to start by gaining the same level of knowledge. There are very few "skeptics" on this site I'd describe as stupid or uneducated. Willful ignorance is a different matter entirely, and it's perfectly compatible with intelligence and education. In other words, I really don't understand what apirate is hoping to accomplish with this line of argument.
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  24. Actually thoughtful @122 Working on your request...
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  25. Archiesteel @ 112 "If you're going to go with Argument from Popularity, you should consider that 97% of publishing climate scientists support AGW theory. I'd argue you're basically saying that only 3% of climate scientists are both onest and competent. That's an extraordinary accusation, and one made without evidence. How is that not smearing the good names of thousands of hard-working scientists?" I am going to politely ask you not to put words in my mouth. Your statement reflects your own biases, and emotions. If you read my original statement that you quoted, but apparently failed to digest, it states, "most researchers are honest people." The entire point of my post, and I will try to be extremely direct, is that there are institutions with more liberal leanings and those that are more conservative. For example in the USA, Cal-Berkeley, or Occidental (very liberal) vs. West Point or Texas A&M (very conservative). If all things are considered, and all of the above institutions had equal sized science departments, equal research resources, equal funding, etc..., which would you gravitate toward?
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    Moderator Response: [Daniel Bailey] Please refrain from making ideological statements. Try to adhere to the topic of the post. Thanks!
  26. What is the point of youp point - ideology trumps science? It seems that you are putting the cart ahead of the horse and declaring if all things were equal that the cart could pull the horse just as well as vice versa.
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  27. apirate: The entire point of my post, and I will try to be extremely direct, is that there are institutions with more liberal leanings and those that are more conservative. For example in the USA, Cal-Berkeley, or Occidental (very liberal) vs. West Point or Texas A&M (very conservative). If all things are considered, and all of the above institutions had equal sized science departments, equal research resources, equal funding, etc..., which would you gravitate toward? I may get moderated for this, but why are you wasting our time with yet more idle speculation? You've been asked again and again and again to provide some evidence to back up your claims, and you've delivered virtually nothing but opinion, speculation and situational ad hominem. You either understand the science or you don't. And almost everything you've posted here strongly suggests that you don't understand it, and are therefore trying to drive the conversation toward ideology. Adding insult to injury, you don't have evidence or good arguments for your views on that subject, either: all you have are question-begging appeals to "common sense," prejudice and -- inevitably -- situational ad hominem. People here have been incredibly patient with you. Why don't you return the favor by making a substantive, coherent, scientific argument, instead of continually changing the subject and moving the goalposts?
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    Moderator Response: [Daniel Bailey] Agreed. This has gone on long enough. Future off-topic comments will be deleted. Thanks in advance to all for your compliance!
  28. David Horton at #3 - "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)." Not really astronomical. You could just as easily say the natural cycle is coinciding with the massive outpouring of carbon dioxide. We are in a warm phase and human populations, along with other organisms, explode. It stands to reason that we are likely to have high populations during these and the development of technology would occur then.
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  29. Archie, just curious as to how many total scientists that 97% represents. Thanks, MG
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  30. Marvin Gardens, have a look at Scientific Consensus
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  31. #128: "could just as easily say the natural cycle is coinciding with the massive outpouring of carbon dioxide." Yes, you could say that. As shown here, the really massive outpouring of CO2 took off right after WW2. About 50% of the cumulative (area under the annual emissions curve in that graph) occurred since the 1970's. What 'natural cycle' is this? What causes it? And what evidence do you offer for its existence? See the thread Empirical evidence that humans are causing global warming to see how it's done at SkS. Data, analysis and peer-reviewed science trump 'you could just as easily say.'
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  32. Murph at 130 - I looked at the link within SKS, and then went to the original site. The 97% figure represented only 79 scientists?
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  33. Marvin Gardens, there was a lot more than one link there. Did you miss the list of scientific organisations ? The 1,372 climate researchers in the Andereg paper ? The Oreskes study ? Can you see a pattern there ?
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  34. I’ve been asked to provide my scientific reasons for not supporting the AGW hypothesis. A short explanation follows. (Sorry for the delay, I’ve been working this past week on delineating a wetland to help minimize the effects of running a 4 mile wastewater effluent pipeline.). In statistics, a null hypothesis is a hypothesis that is presumed true until statistical evidence in the form of a hypothesis test indicates otherwise. For example, in a clinical trial of a new drug, the null hypothesis might be that the new drug is no better, on average, than the current drug. We would write H0: there is no difference between the two drugs on average. Special consideration is given to the null hypothesis, due to the fact that the null hypothesis relates to the statement being tested, whereas the alternative hypothesis relates to the statement to be accepted if/when the null is rejected. H0 can be “not rejected”, or H0 can be “rejected in favor of H1”. It can never be concluded to "reject H1", or even "accept H1". “Not rejecting H0", does not necessarily mean that the null hypothesis is true, it only suggests that there is not sufficient evidence against H0 in favor of H1. Rejecting the null hypothesis then, suggests that the alternative hypothesis may be true.. Prior to discussion of the anthropogenic global warming (AGW) hypothesis it should be established that the Earth’s climate has gone through relatively extensive cyclical changes in temperature throughout its history. In the case of warming, the lag between temperature and CO2 is explained as follows: as ocean temperatures rise, oceans release CO2 into the atmosphere. In turn, this release amplifies the warming trend, leading to yet more CO2 being released. In other words, increasing CO2 levels become both the cause and effect of further warming. This positive feedback is necessary to trigger the shifts between glacials and interglacials as the effect of orbital changes is too weak to cause such variation. Additional positive feedbacks which play an important role in this process include other greenhouse gases, and changes in ice sheet cover and vegetation patterns. If changes in the Earth’s orbit can initiate warming changes, then the opposite must be true: changes in the Earth’s orbit can initiate cooling changes, as the feedbacks listed above become negative. Also, as the world is coming out of the Little Ice Age it is only reasonable that the Earth is experiencing a gradual rise in temperature. The fundamental AGW hypothesis is based on the following scientifically verifiable facts: 1) CO2 is a greenhouse gas (GHG) and contributes to the greenhouse effect by absorbing and emitting radiation within the thermal infrared range thus warming the Earth. 2) Through the use of fossil fuels over the past 150 years, humans have contributed to the current rise in atmospheric CO2 levels from 280 ppm to 390 ppm. The AGW hypothesis (H1) then basically states that: current human CO2 emissions significantly affect the climate outside of natural variations. Therefore, the null hypothesis (H0) is: human CO2 emissions do not significantly affect the climate and the variations are the result of natural processes. There are a number of rational and viable scientific objections that have been raised against various parts of the hypothesis, from the nature and sign of the forcings considered and unconsidered, to the existence of natural thermostatic mechanisms. It is the onus of the supporters of the H1 hypothesis to establish enough evidence to reject H0. That is, show where the climate has changed from any historically established norms. First, the climate must be acting significantly anomalously or abnormally. Second, the anomaly must be explained by human actions. And, third modeling (predicting) cannot be used as explanations or facts. At this point, for the sake of brevity, I will end this post. I have rebuttals prepared for examples you supporting AGW you will want to post.
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  35. #134: "I’ve been asked to provide my scientific reasons " And you produced ... absolutely nothing, nada, ne rien, nichts, nichevo ... except a lecture on the null hypothesis. Thanks for that. And thanks for brilliantly demonstrating the utter bankruptcy of the denialist position. The remainder is regurgitation of the points you've tried to make for the past week or so. No new science, no new data, no new published research, no new insights. Example: "There are a number of rational and viable scientific objections that have been raised ..." What objections, raised by whom? Supported in what way? But those are purely rhetorical questions, I doubt if there's any interest in your repeats of the same-old same-old any longer. People here are interested in issues of substance.
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    Moderator Response: Also pretty much off topic.
  36. Muoncounter, Following are the decadal trends (in degrees F) from NOAA from the North American continent. The trend is 0.12 degrees F rise per decade for the lifespan of this record source. The website is www.noaa.gov Bankrupt? I think, not. Your job, according to accepted scientific doctrine, is to explain how 0.12 degrees F per decade for a planet coming out of an ice age is abnormal. Also, what do you think about that drop in temp for the last decade? decade trend average 1900 - 1909 -0.54 52.36 1910 - 1919 -0.8 52.14 1920 - 1929 -0.73 52.57 1930 - 1939 0.21 53.37 1940 - 1949 0.13 52.84 1950 - 1959 0.37 52.96 1960 - 1969 -0.37 52.46 1970 - 1979 -0.51 52.45 1980 - 1989 0.26 53.07 1990 - 1999 0.71 53.6 2000 - 2009 -0.72 54.01
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  37. Interesting discussion, but I didn't see much discussion about the ENSO/NOI/SOI cycle, which is one of the most well-known natural oceanic cycles (is it a cycle?). There are, however, one or two posts stating that the ENSO cycle only causes short term effects and the net-energy balance is zero (e.g. comment #22). However, that would only be the case if el ninos and la ninas were of the exact same magnitude, same volume, and occur over the same length of time. If not, there will be an energy imbalance: more and stronger el ninos over time compared to la ninas will cause more heat to be released and vice versa. I have posted here how the PDO and ENSO cycle are linked, and how el ninos have increased in number and strength compared to simultaneously -and at the exact same rate- decreasing la ninas (both in nr an strength) over the last few decades. To be more specific: looking at the NOI data the last decade (2000-2011) has been dominated by el ninos: 37 el nino months vs. 26 la nina months (including the current la nina), whereas the years prior to the last decade (1950-2000) it was the other way around: 145 el nino months vs 175 la nina months. For the entire data-record (1950-2011), la ninas still dominate: 200 la nina months vs 182 el nino months. However, since 1975 (about the year that is often found since when global atmospheric temperatures started steadily increasing) el ninos have dominated both in number of months and peak-strength: 120 el nino months vs. 93 la nina months, with an average strength of +1.1 +/- 0.5 and -1.0 +/- 0.4, and a an absolute peak strength of 2.5 and -1.9, respectively. Hence, not only were there 12% more el nino months, these were also on average 10% stronger, compared to la ninas during the same time period. In addition, the peak el nino (1998), being 24% stronger than the peak la nina (1988). This trend-reversal from a la nina dominated to an el nino dominated cycle got even stronger in the last decade, which interestingly is also the warmest decade on record. Now I am NOT saying the ENSO cycle can explain all global warming since the 1970s/1980s, certainly NOT, but the ENSO cycle can -given its developments over the last few decades- not be dismissed as having no effect by the simple statement that "they -el ninos and la nina- cancel each other out", as they clearly haven't over the last decade and last 3 decades for that matter. ps: please don't plot CO2 levels using a y-axes from say 300pm to up to 400pm; that's scientifically dishonest. You need to have a true 0. Doing so, the increase all of a sudden looks less dramatic... is that maybe the reason why it's often plotted dishonestly? pps: I still have difficulties in understanding how a trace gas that comprises 0.04% of the atmosphere (compared to N2: 78% and O2 19%) can have such a large impact, especially since the change in atmospheric composition is a little over 0.01% over the last 100 yrs. Maybe there are some good posts on this?
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    Moderator Response: You need to stop typing long enough to actually read through the extensive list of Arguments. Also use the Search function. Split your comments into chunks narrowly focused on each of those.
  38. Muon From NOAA.gov for the North American Continent, are the annual temperature averages. Pardon the formatting, but it should be clear. Do you need more? Where is the abnormality? Year Temperature Degrees Farenheit 1998 55.08 2006 55.04 1934 54.83 1999 54.67 1921 54.53 2001 54.41 2007 54.38 2005 54.36 1990 54.29 1931 54.29 1953 54.16 1987 54.11 1954 54.11 1986 54.09 2003 54.02 1939 54.01 2000 54 2002 53.94 1938 53.94 1991 53.9 1981 53.9 2004 53.84 2010 53.76 1933 53.74 1946 53.72 1994 53.64 1900 53.53 1941 53.47 1995 53.45 1988 53.36 1992 53.34 1977 53.33 1925 53.22 1910 53.19 1980 53.15 2009 53.11 1956 53.11 1952 53.1 1973 53.08 1974 53.05 2008 53.02 1997 53.02 1963 53.02 1959 52.9 1949 52.88 1957 52.86 1936 52.86 1943 52.85 1927 52.83 1908 52.83 1896 52.8 1911 52.78 1922 52.77 1984 52.76 1958 52.75 1930 52.71 1947 52.7 1926 52.68 1962 52.66 1901 52.66 1983 52.65 1944 52.65 1961 52.64 1928 52.63 1996 52.62 1940 52.62 1918 52.62 1942 52.61 1935 52.61 1914 52.6 1967 52.56 1906 52.53 1989 52.52 1945 52.5 1955 52.49 1932 52.48 1971 52.47 1964 52.46 1965 52.44 1902 52.43 1948 52.42 1923 52.41 1970 52.4 1913 52.33 1937 52.29 1975 52.28 1969 52.27 1919 52.27 1897 52.27 1976 52.26 1966 52.26 1907 52.26 1960 52.22 1950 52.21 1915 52.2 1909 52.17 1972 52.15 1898 52.12 1968 52.11 1982 52.08 1985 52.03 1993 52 1904 51.96 1951 51.91 1978 51.82 1905 51.8 1920 51.78 1899 51.73 1979 51.67 1929 51.58 1916 51.57 1903 51.49 1924 51.31 1895 51.21 1912 51.03 1917 50.82
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  39. WHATDOWEKNOW @ 137 Nice post. I hate to admit it, but I never though of the Y axis scale issue for CO2. I've also never gotten a real answer from anyone on how the "normal" temperature or "normal" CO2 levels were derived.
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  40. WHATDOWEKNOW I agree with what you posted Here is an interesting graph of PDO vs temperature smoothed 5 yr http://www.woodfortrees.org/plot/hadcrut3gl/from:1940/to:2010/scale/plot/jisao-pdo/from:1940/to:2010/mean:60/plot/hadcrut3gl/from:1940/to:2010/scale:5/mean:60 The PDO seems to act like the first derivative of the temperature IE: if the PDO is above the 0 line there is warming and if it is below the 0 line there is cooling. [Ignore trends] From 1940 to 1978 the PDO is negative and there is cooling. Since a negative PDO means there will be more La Nina's than El Nino's there should be cooling and there is. From 1978 to 1998 the PDO is almost continuously positive so there are more El Nino's than La Nina's and it should warm. It does exactly that. Since 1998 there has been both positive and negative PDO and the temperature has gone sideways. The raw data is here and you can pull it into Excel and graph it yourself. http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml It takes 15 minutes tops. So why does it take CO2 & aerosols to explain the warming cooling and staying the same we have experienced since 1940 ?
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  41. Apirate, Thank you for responding. You have chosen "AGW fails because its defenders haven't passed the "null hypothesis test"". The very first thing you need to consider is - what is the null hypothesis? For example, in your drug example at the beginning of your post "H0: there is no difference between the two pain killing drugs (effect on people) on average." Now consider a more accurate HO "HO: there is no difference between the two drugs (effect on people (however we took the liberty of injecting morphine into the patients while testing drug b)) on average." I am perhaps being too cute in pointing out that you have chosen the wrong null hypothesis - and a very, very dangerous experiment. The correct null hypothesis is: The world will warm by .12C/decade WITHOUT any CO2 added my man. The null hypothesis is ALWAYS the one you futz with the least. This bizarre, crazy, DANGEROUS experiment of releasing CO2 into our atmosphere is not a null hypothesis; it is the height of folly. So your argument falls flat (as some poster pointed out in a rather colorful manner above). I am all in favor of using logic and facts to solve this problem. But you must use logic, and not fake logic or false logic. Now that fact that climate science has already proved even your twisted null hypothesis false (ie they have demonstrated beyond a reasonable doubt the climate is warming, correlated with CO2) is beside the point. So please consider revising your logical frame. You have defined things such that the truth is hard to see. There is no need to do so. Use logic and facts to find the truth. Now, looking at the data you provide - please do not use North American temperature as a stand in for global temperature. Again, confusion reigns. You list a column of data that purports to show that the earth has been warming by .12C/decade since 1880. This is simply not true. Please examine the data and respond with a more accurate statement (namely that warming without remission (as opposed to natural variation) is plainly visible from 1980 on, prior to that time it is not). If you state global temperatures, and look at them clearly (many, many graphs show this) you will see your data does not support your theory. If you can take the larger step of being willing to look at the problem a different (and fundamentally more correct) way you can break out of the confusion you have on this issue. Respectfully, Tom
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  42. The PDO bit has been debunked a number of ways. One thing your analysis misses is the current La Nina is the strongest on record (and don't forget - STILL in that solar minimum). Yet we are warming.
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  43. apiratelooksat50 - "I've also never gotten a real answer from anyone on how the "normal" temperature or "normal" CO2 levels were derived." - I believe that's incorrect. The "normal" CO2 level would be under 285, as it has been for the last half million years. The "normal" temperature without the CO2 forcing would be ~0.8 C, lower than it is at the moment. I know I've told you this (among others), and pointed you to the appropriate topics. Please - don't ignore the input you receive. It does not portray your opinions in a good light.
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    Moderator Response: [Daniel Bailey] Fixed text.
  44. Re: strongest La Nina on record, where does that claim come from? Doesn't look that way here: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml
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  45. Moderator @ 135: How is this off topic when the topic is "Could global warming be caused by natural cycles?" and I am supporting my stance on the subject?
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    Moderator Response: You really, really, need to spend some time reading the Arguments you can see listed by clicking one of the Arguments links. A strength of this Skeptical Science site is the ease of finding information about each specific topic. When you have a claim about a topic that is the focus of a narrow Argument or Post, you should comment there. Short mentions are okay on more general threads, but with pointers to the more relevant threads for continued discussion.
  46. #136, 138: Like I said, not interesting. Obviously, you missed the fact that 2010 ties for hottest year ever. In a decade that set more high temperature records than the prior decade, which set more high temperature records than the prior decade, which set more high temperature records than the prior decade. There are no natural cycles that do that. But you haven't proposed any; it seems that you will just go on saying 'no its not.' There are places on the web where you can get away with that, but not here. And that '0.12F/decade you're quoting is flat incorrect: do you not know the difference between C and F? See Northern hemisphere warming rates and half a dozen other threads on temperatures. BTW, we 'came out of the LIA' decades ago, so you can stop repeating that. Besides, its a topic for another thread.
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    Moderator Response: Specifically, see "We’re coming out of the Little Ice Age."
  47. AT @ 140 "(they have demonstrated beyond a reasonable doubt the climate is warming, correlated with CO2)" I agree with this part of your statement, especially since you said correlated and not caused by. Certainly the climate is warming as I stated in my original post. Because the AGW theory is pinning current "excessive warming" (what a vague term that is) on human emissions, and that is a change from at least 400,000 years of climate data (see #105), then the H0 remains as I stated it. For instance, with these horrific floods in Brisbane, using your rationale, it would be put upon me to prove that humans are NOT the cause of the flooding. The usual null hypothesis is what is normally observed in nature. By saying that GHG's cause the warming, then that negates all the other inputs that we know whether forcings or feedbacks. I really do appreciate your civil conversation on this matter. Thanks.
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    Moderator Response: "Excessive warming" is not vague; there are very specific predictions, and some already consequences. Take your comments on that to "It’s not bad." You are wrong that "By saying that GHG's cause the warming, then that negates all the other inputs that we know whether forcings or feedbacks"; see "CO2 is not the only driver of climate."
  48. @ muoncounter (146) I thought you sank the battleship with that "bankruptcy" bit. The Yooper
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  49. Actually thoughtful You just made up the part about "The current La Nina is the strongest on record" The data doesn't support you. http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml The last several months have shown cooling, and that is the time frame of the La Nina. http://www.drroyspencer.com/ Sept .477 Oct .306 Nov .273 Dec .182 Does that look like warming ? Over long or short time periods the temperature follows the ratio of El Nino/s to la Nina's. http://www.woodfortrees.org/plot/hadcrut3gl/from:1940/to:2010/scale/plot/jisao-pdo/from:1940/to:2010/mean:60/plot/hadcrut3gl/from:1940/to:2010/scale:5/mean:60 [The When the PDO is positive there are more El Nino's than La Nina's and it always warms unless there is a volcano or some other natural event. When the PDO is negative it cools. Funny how that works.] The whole 1978 to 1998 warming happened when the PDO was positive. The cooling from 1940 to 1978 was when the PDO was negative. CO2 isn't needed to explain the temperature from 1940 to present.
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    Moderator Response: [Daniel Bailey] Please take all future comments on the PDO to the http://www.skepticalscience.com/Pacific-Decadal-Oscillation-intermediate.htm thread. If it also pertains to your discussion here, post the relevant bit on the PDO at the linked thread and then provide a link back here to the comment you posted over there. Future off-topic comments here will be deleted. Thanks for helping us keep a clean house!
  50. #148: Yooper, A classic! But this is more like the Battle of New Orleans
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    Moderator Response: [Daniel Bailey] Nice! Caught me listening to this one. The good old days, before the CO2...

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