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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 151 to 160 out of 160:

  1. #142, the current la nina is absolutely NOT the strongest on record, but instead so far ties with 2008 (the weakest in a series of decreasing la ninas since 1975, see my previous posts). The OND and SON seasons for the current la nina are -1.4 each. The record so far is for 1973: -2.1. FYI: the '09/'10 el nino was 1.8 (currently 22% stronger than the current la nina) and the record el nino of 1998 was 2.5. Similar to el ninos, la ninas tend to peak around the December time frame. Given the current development (of the last two seasons: -1.4) it is highly unlikely the current la nina will become much colder; if any. However, compared to el ninos, la ninas tend to linger a little longer whereas el ninos show a more "spiky" character. I recently read an interesting NOAA statement on ClimateWire (paid subscription, can't link) regarding 2010 being a tie with 2005, which was -according to the statement- "due to the la nina that developed (which started officially in July 2010), cooling things down. And if it wasn't for the la nina we would have THE warmest year on record." OK... how about the fact that we had the 4th strongest el nino winter '09/'10 on record and that global temperatures always lack 3-6 months in response to ENSO events; the atmosphere is just starting to respond to the la nina in other terms, and 2010 temperatures are therefore at the earliest affected Nov/Dec 2010 by the current la nina. (this is a well-known fact, hence why for example the NASA data point for Dec 2010 is .40 compared to .74 in Nov). Hence, it is more correct to say that due to the past el nino we have a temperature tie with 2005. Or in other terms, if we hadn't had that el nino -or neither the la nina- where would 2010 then rank?
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  2. #151: "it is more correct to say that due to the past el nino we have a temperature tie" That seems like a lot of fancy tap dancing to explain what clearly stands on its own. "If the warming trend continues, as is expected, if greenhouse gases continue to increase, the 2010 record will not stand for long," said James Hansen, the director of GISS. Perhaps one should ask 'why was this el Nino so strong? why is the following la Nina also so strong?' Perhaps there is somewhat of a longer term mechanism driving those oscillations. But ask those questions on the appropriate thread.
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  3. Moderator I totally disagree! The discussion about the PDO belongs on this thread. The name of this thread is "Could global warming be caused by natural cycles?" The PDO is a natural cycle and I [and others on this thread] contend the warming from 1978 to 1998 can easily be explained by it. The period 1978 to 1998 is the only period when there was unequivocal warming which has been linked to CO2 [incorrectly in my opinion] From 1998 to present it s debatable whether there is any warming. If so it is slight at best.
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    Moderator Response: [Daniel Bailey] As you well know, having commented on the PDO thread several times (and been corrected several times there), in-depth discussions of various topics at Skeptical Science need to be placed on the appropriate threads. As you were counseled before, you maywill need to learn to use the Search function to do that. Discussions on PDO belong on the PDO thread already linked for you. As for the "no warming since 1998" meme (you are aware, aren't you, that 2005 and 2010 were both hotter than 1998?), removing the impact of natural cycles like ENSO and other things like volcanoes, explain this (from Open Mind):
  4. NETDR @153, Feel free to quantitatively demonstrate that "The PDO is a natural cycle and I [and others on this thread] contend the warming from 1978 to 1998 can easily be explained by it." on the appropriate thread. IMHO, you would probably have better luck explaining more of the variance in the global SAT record using the AMO than the PDO. "From 1998 to present it s debatable whether there is any warming" Also on the wrong thread, and you seem to have been hoodwinked by Monckton et al's misinformation. Robert Way uses various datasets to dismisses that myth here. This will suffice for now:
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  5. Eric (skeptic) My information comes from NASA. "The solid record of La Nina strength only goes back about 50 years and this latest event appears to be one of the strongest ones over this time period," said climatologist Bill Patzert of NASA's Jet Propulsion Laboratory in California." The language was clear than I remember, so I can live with "one of the strongest". (the link is long, and my patience short - you can google the quote and see the story - it is not the data, but Bill Patzert's analysis.)
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  6. Apirate, There isn't much I can do if you insist up is down and down is up. The null hypothesis is the one where you don't monkey with the system. Pumping in 6,000,000,000 tons annually of CO2 into a basically closed systems is a textbook example of monkeying with the system. Take a look at : http://www.skepticalscience.com/human-co2-smaller-than-natural-emissions.htm I admire those of you in a quixotic battle with reality, but I do think it requires being impervious to some important facts to maintain, for example, that it is PDO, or ENSO. Natural cycles are, by definition, cyclical. For natural variability to be in play, what went up must come down. Barring an external forcing (which our clever climate scientists tell us is CO2 - but you want to ignore that, which leaves us with NO forcing) - the longest cycle ever claimed is a 60 year cycle. If you start in 1950 you are toast (we are at 60 years - no cooling). If you start at 1980 - (and ignore lots and lots and lots and lots of counter-facts) - you have 30 years of non-stop cooling to get this cycle to come back to the 1980 start. Good luck. I don't mean to be rude but you have broken my system - it only works when you use facts and valid logic. You came back with a muddled logic, which is so confusing that you can't properly frame the topic - or even see how bad your initial conceptual frame is. I urge you to come up with another way of thinking about it - as your starting position is one that I (pessimistically perhaps) think you won't be able to think your way out of until the data is even more overwhelming. Here are some ideas for other approaches (if it helps, we can call the your first effort a draw, as I am at a loss as to how to throw you a logical life preserver - your concept is internally consistent, but doesn't allow you to recognize reality until a scientific proof is available). Recognizing, of course, that science doesn't have proofs. Science has theories. Theories that explain the world, and are considered "generally accepted" when there is no better theory available and the preponderance of evidence supports the theory. This is the case with climate science (sometimes called AGW). So here are some ideas and ways to think about it that should avoid the shoals of your flawed null hypothesis. 1. Why is warming more at night? 2. What evidence will convince you that AGW is correct? What will convince you it is false (bonus if you can get to your "final answer" within the decade). 3. Can you offer off a complete theory with an equivalent level of explanatory power (if you understand CO2 and greenhouse gases are causing the warming, you can explain coral reef bleaching, rising sea levels (and their rate), changes in weather patterns, loss of mass at arctic and Greenland ice sheets, loss of mass at the South Pole and on and on). If your mind takes you to the null hypothesis - fight the magnetic pull of that closed circle argument. Once you get back on that track you could find you have no escape (there is, but it requires getting out of that endless loop).
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  7. #155. Please see my previous comment (#151). The current la nina is NOT the strongest on record. Current SST anomalies are about the same (0.1C lower) than the 2008 La Nina which was the weakest "peak" la nina since 1975 and the lowest "peak" la nina since 1950. (unfortunately I can't past a pictures here, otherwise you'd see exactly what I mean, but I can refer to my another post to give you an idea: here; #13. Now, time will tell if the current la nina will get any or much stronger, though most indications don't point that way. Also, and as I pointed out previously, global temperatures LACK 3-6months behind in response to ENSO events. Hence, most of the atmosphere won't respond until right around now...
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  8. #152. if it is equally OK to say that it's a tie because of the la nina, it is equally OK to say that it's a tie because of the el nino. Actually it is more correct to say the latter due to the 3-6 months lack in response in global atmospheric temperatures to ENSO events and since the el nino was during fall-winter '09 through spring '10, whereas the la nina didn;t start until june/july '10 this delayed response caused '10 to be obviously mainly affected by the el nino and not the la nina. Please stop tap dancing to your own little drum and also accept facts that do not (always) support your thoughts and theories. Just because 2010 was a tie with 2005 and since it was an el nino year doesn't mean there is no AGW, it simply means that it was warmer because of an el nino (and AGW?). Just because there may be AGW doesn't mean global natural cycles have no influence on global temperatures anymore. They always have and always will. Please remember: no matter how beautiful the guess is, or how brilliant or famous the guesser is. If in the end the experiment shows the guess is wrong than that's all there is to it.
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  9. Muon @ 146 I know the difference between C and F. Apparently you failed to follow my link. I plainly referenced I was using the NOAA website and provided the link. It uses Imperial units. The website allows you to look at data from 1895 to 2010. I used their software to generate graphs and data pertaining to each decade by using the most recent 12-month period for rankings. Go check it out. "BTW, we 'came out of the LIA' decades ago, so you can stop repeating that. Besides, its a topic for another thread." I did not reference the LIA in that post. I referenced only the ice age, and it stands to reason the Earth warms coming out of a cold period. Are you going to answer about the temperature drop over the last decade? The decadal average is 0.12 F over that time period for a total rise of 1.26 F.
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    Moderator Response: If you actually read the original post of this thread, you will see "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)."
  10. WWDK @158, "Just because there may be AGW doesn't mean global natural cycles have no influence on global temperatures anymore. They always have and always will." You are making a classic strawman argument there. Nobody int he know here is denying that the climate system has internal modes (e.g., ENSO, AMO), nor are they denying that they do modulate global SAT record to some extent. What these transient internal climate modes (which are cyclical by nature) do not explain is the sustained, long-term warming that is observed in the SAT record. An El Nino alone does not explain the current global SAT anomaly of +0.63 K (GISTEMP) relative to the 1951-1980 baseline, nor does it explain the +0.85 K warming observed since circa 1880. ENSO perturbs global annual SATs by about +/- 0.1 K, and at most about +/- 0.2 K for a strong event (Trenberth et al. 2002). From Tsonis et al. (2005): "Note that the contribution of ENSO to the long-term temperature trend in the last 50 years is about 0.06 C or 10% of the overall trend [Trenberth et al.,2002].However, as Figure 2a indicates, after a time scale of the order of 16 (5 + 11) months, El Nino’s role is to reverse that tendency." So much for the (false) claim made here and elsewhere that natural cycles are being "ignored" by climate scientists. To suggest so is incredibly patronizing to climate scientists.
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  11. WDWK @ 158 - You should read this Tamino piece, which Daniel Bailey noted here. Accounting for and correcting the various known cycles, the underlying trend is very clear.
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  12. #160, thanks but I am not saying climate scientists are ignoring or denying these cycles. I am referring to this original post that claims: "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." which I find to be a strong argument and therefore I am saying "Just because there may be AGW doesn't mean global natural cycles have no influence on global temperatures anymore. They always have and always will." I am saying nothing more, nothing less with that statement. I am not accusing anybody with that statement either, it's simply open and true. I am sorry you misinterpreted it and perceived it the way you did. Of course does an el nino alone or all el ninos combined for that matter not explain the current temp anomalies. I never stated that either. But we agree that el ninos and la ninas significantly affect global temperatures. That said, please look again and my comment #137 where I show how the ENSO pattern has changed the last 35 years and even more so the last 10 years, shifting from la nina dominated to el nino dominated events. How does that fit in is my question.
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  13. #161. Why did they use MEI? That's a ranked-value, based on 6 variables many of which not related or only indirectly related to temperature. MEI is not an actual measurement. MEI is not a temperature anomaly, such as NOI or SOI. hence, I don't see how subtracting a rank from a temperature anomaly produces anything meaningful. Please explain if it does.
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  14. #162: "I show how the ENSO pattern has changed the last 35 years and even more so the last 10 years, shifting from la nina dominated to el nino dominated events" And why do you think that is? What has happened that could shift a fairly regular oscillation so dramatically? From Yeh et al 2009, el Nino in a changing climate: Recent studies show that the canonical El Niño has become less frequent and that a different kind of El Niño has become more common during the late twentieth century ... the central Pacific El Niño (CP-El Niño; ... ), differs from the canonical eastern Pacific El Niño (EP-El Niño) in both the location of maximum SST anomalies and tropical–midlatitude teleconnections. ... we find that projections of anthropogenic climate change are associated with an increased frequency of the CP-El Niño compared to the EP-El Niño. ... the occurrence ratio of CP-El Niño/EP-El Niño is projected to increase as much as five times under global warming. -- emphasis added So given that you agree that AGW exists (ref #158); what was once a 'natural cycle' may no longer be so natural.
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  15. WDWK @162, To be honest I really do not know what you are trying to suggest with your posts. It seems that you agree with the main thrust of the OP, so why then reiterate your straw man argument? You are raising a moot point. Tsonis et al. (2005) purport that: "Thus, in a warming climate El Nino events will be more frequent than La Nina events. That transition, if it comes to be, would act to further enhance the long-term underlying warming from the escalating radiative forcing from anthro GHGs.
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  16. @pirate: "I did not reference the LIA in that post. I referenced only the ice age, and it stands to reason the Earth warms coming out of a cold period." We are way past the Holocene Optimum. Temperatures should be cooling now, according to the paleoclimatic record. They aren't.
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  17. #159: "the temperature drop over the last decade?" It's been clearly established on numerous threads that a decade is an insignificant time period. This is climate, which most of us understand to encompass a 30 year time frame. Expand the link under 'Climate definitions' to see "Normals are generally averages of climate elements such as temperature or precipitation over a 30–year period". But let's look at the last decade: --from Science Daily 2000-2009, aka the warmest decade on record. As for your 0.12F 'trend', every credible temperature reconstruction finds 0.13-0.3C/decade, as illustrated here. -- Assessing surface temperature reconstructions Once again, you really would benefit from doing some reading here at SkS as well as reading some actual research. If nothing else, your arguments would improve. I mean that sincerely, because at the current level, they haven't been very interesting.
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  18. Muon, What websites do you find acceptable for research that you would direct me toward? Pirate
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  19. I'm currently pursuing a M. Sci. in Environmental Systems Engineering at a major liberal arts university in the US. I'm completing a research paper on AGW and it's relationship to climate change. A google search eventually led me to this site. My personal beliefs on AGW and climate change are that the climate has historically changed due to various natural cycles. There are macro-cycles and micro-cycles due to many, many reasons. The latest influence is the increased CO2 due to anthropogenic sources. This increase in CO2 almost certainly has an effect. My extensive research has led me to formulate an opinion. My professor requires us to look at research from various institutions in order to have a complete and balanced input before we generate our output. This site is generally scientific and has been valuable to me. Climate change is a natural and cyclical phenomenon that has occurred over the history of this planet. The normal state of the planet is to be glaciated. We are currently in an interglacial period and according to the timescale are clos to the descent into another glacial period. Atmospheric CO2 levels are rising beyond historical levels. This is almost certainly due to the contributions from humans. It is reasonable to expect these rises in CO2 to contribute to further warming, i.e. climate change. The severity of these changes cannot be accurately determined, though some modeling is predicting the possibility of dire consequences. I do not personally believe that increased levels of CO2 can initiate major changes in the climate. I do believe they can contribute a great deal to climate change. A classmate of mine is conducting research into increased CO2 levels in greenhouses. She has shown increased yield and more vigorous growth from corn, beans and roses. Qualitative and quantitative improvements have been noted. She has not detected any statistically valid difference in temperature. As a legitimate question, does anyone here know why this has not occurred or where she might find some previous research on the matter? Unfortunately, politics and profiteering have entered the scientific discussion. Battle lines have been drawn and the various "sides" are digging into the sand and very little, if any, constructive debate is going on. Legislated change is unlikely to occur. This is unfortunate, because it appears little will be done to prevent any changes and the world will have to switch from a mode of prevention to a mode of reaction. If necessary.
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    Moderator Response: See "It’s not bad," "CO2 is not a pollutant," and "CO2 effect is weak." And "Models are unreliable." Usually the comments have additional, excellent information; for example, you'll find links to the U.S. Dept. of Agriculture's report on CO2 and temperature's effects on crops. You also should skim the list of Arguments you can get to by clicking the "Arguments" link in the horizontal blue bar at the top of the page. And don't hesitate to use the Search field at the top left of the page.
  20. #169: "completing a research paper on AGW " Are you actually researching the science of AGW? It sounds like you've already formed your conclusions. "normal state of the planet is to be glaciated." Really? During what time period? You might want to check your sources for that. Be aware that on this site, you need to show your work and avoid making sweeping unsubstantiated generalizations (especially those that are false). "I do not personally believe that increased levels of CO2 can initiate major changes in the climate. I do believe they can contribute a great deal to climate change." In a science paper, your personal beliefs shouldn't interfere. You should look at prior threads Its not us, Its a natural cycle and CO2 is not the only driver. Preferably, for your grade's sake, before you form your conclusions.
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  21. #168: Pirate, Try Google Scholar. Type a search phrase such as 'climate change natural cycle' and look at the published science that becomes available to you. That search just gave me 1.39 million results, but the even just the top 30 or so might do.
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  22. Sasquatch, has your classmate taken into consideration that greenhouses have temperature regulation mechanisms? I mean, the whole point of a GH is to have optimized conditions. Was her study exclusively on GH with enhanced CO2 and disabled temperature regulation systems? Why would anyone do that? I have to wonder what exactly was the experimental design here. I don't know what is in your classmate's paper but the way you describe that particular point makes little sense. If you are going to include some of your statements above in your paper, you want to remove the "almost certainly" from them in order to be more credible. It is not almost certain that CO2 has an effect on climate, it is absolutely certain. You may argue if you want that the effect is too small to be consequential or whatever. But saying that it is almost certain is like saying that CO2 almost has radiative properties. By the same token, it is certain that the increased atmospheric CO2 comes from human activity. The isotopic signature clearly shows it. This site has posts on the subject. I don't understand what you mean by "research from various institutions." Research comes from researchers. It is published in peer-reviewed journals. Institutions producing research are usually universities but if the research is not in serious, well established peer-review publications, you should stay away from it, regardless what institution is involved. Stuff called research that comes from think tanks with an agenda is useless. I doubt that papers squeaked by in low impact journals or publications of dubious quality are an asset in a thesis paper. There is so much in the legitimate litterature anyway that there is no need to use subpar sources. And last point: not to be pedantic but if you're writing a PhD paper, watch your spelling. "it's" is the contraction of "it is", not the possessive. If you repeat it a few times, its true nature as a grammatical error shows and it's no longer forgiven as a typo. Everyone makes the confusion in the media and elsewhere but a graduation research paper must be better than that.
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    Moderator Response: Sasquatch, if you reply to these questions, please do so on the appropriate threads. For example, to discuss the roles of CO2 and temperature on plant growth, comment on one of the two relevant threads I pointed you to earlier. You can post a short comment on this thread, pointing to your comment on that relevant thread. That also applies to anyone responding to Sasquatch's original comment here. Further off topic comments will be deleted.
  23. I have replied to Sasquatch on the It's not bad thread.
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    Moderator Response: Thank you for redirecting the conversation!
  24. #164 muoncounter. I don't know what has shifted this. I don't believe it is only AGW. That simply makes no sense (on a global scale the atmosphere responds to the oceans not the other way around, especially during ENSO events. So why all of sudden should that be the other way around?). If a model predicts/says it's because of AGW, it's simply based on the assumptions put in that model. If one of those assumptions is that AGW will influence ENSO than you have a self fulfilling prophecy. I am just afraid we're reaching that point in climate science and AGW. Clearly the PDO and ENSO are interconnected and we need to better understand that relationship and others (such as solar cycles and their relation to PDO and ENSO) before we say/think it's all AGW. Just because one thinks AGW plays a role, does not mean we should not be critical anymore. We should then be even more vigilant to not contribute the wrong cause to an observed trend.
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  25. whatdoweknow - I would suggest looking at this thread at Open Mind. Tamino (a very skilled time series analyst) has examined the temperature record against the MEI, sunspot numbers, volcanic aerosols, the annual cycle, and a linear trend, since 1975. These factors separate very clearly, back to the records of the input forcings, leaving a slightly noisy linear trend behind, with excellent agreement from all temperature records. ENSO and PDO push energy around - they don't create or destroy it. What changes they make in cloud cover, water vapor, and other radiative forcings is cyclic - and it cancels over a few cycles to no change. CO2 forcings, based on our emissions, quite sadly do not cancel out.
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  26. #174: "I don't believe it is only AGW. That simply makes no sense" And so we reach the inevitable goal line stand. I show you peer-reviewed research that suggests changes to el Nino are based on AGW; that confirms that human activity can and does alter global phenomena. And you can only say 'I don't believe', 'that makes no sense'. "if a model predicts/says it's because of AGW" Models are tests of hypotheses. They do not merely reproduce the input parameters; there is always a free variable. If you want to take issue with the techniques of climate modeling, see the thread Models are unreliable. But if you don't believe models in general, I strongly suggest you refrain from flying, driving, crossing bridges, etc. "We should then be even more vigilant to not contribute (attribute?) the wrong cause to an observed trend." Come on. If someone says your house is on fire, is your first thought to water your lawn? Mountains of scientific evidence point in the same direction, but nope, 'we need to be even more vigilant'. More vigilant about what? Do you apply the same 'vigilance' to unproven ideas about PDOs and solar cycles and the phases of the moon? I'd like to see that in action: one 'skeptic' saying no to another.
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  27. #175. KR thanks for the link; It's been posted under different topics on this website earlier (I think). I have one problem with the MEI: it's a ranking based upon 6 variables, most of which not temperature related. It's neither a measurement, just a multivariate composite index, in which strength of an ENSO event depends on all 6 variables and not on sea surface temperature (anomaly). Thus a strong el nino or la nina, not necessarily means it also exhibits very high or low SST anomalies (as is the case with the current la nina, which has moderate to low SST of -1.4, but ranks high -apparently because several of the other variables are strong-) Hence, I am afraid it's comparing apples to oranges when comparing global temperature anomalies with unit less ranked values. I don't see how one can "correct" temperature with a ranked value. Imo it be more appropriate to use the ONI value, which is a SST anomaly too; unfortunately ONI only dates till 1950.
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  28. whatdoweknow - I would have to agree, the MEI is not perfect. However, as a general index for the strength of the ENSO, it appears to correlate very well to the temperature forcing, as Tamino shows. So - regardless of whether you feel the SST alone is the most important, Tamino shows that the total index of sea-level pressure, zonal and meridional components of the surface wind, sea surface temperature, surface air temperature, and total cloudiness fraction correlates well to actual global temps. That's not really surprising - SST, SAT, and cloudiness are major factors, and winds spread energy around. The only factors I could think of as less correlated would be sea level pressure (due to location dependencies) and possibly winds, so 3-5/6 factors have a distinct influence. I think that your "apples and oranges" analogy doesn't hold up under statistical analysis. The MEI shows an excellent correlation with short term (<5 year) temperature variations, and as such MEI is a reasonable metric for ENSO.
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  29. A link in the latest thread from John Cook (which is very informative, as usual) led me to this : The SOI values confirm that we are in the middle of either the strongest La Niña event on record, or the second strongest. The SOI values for October 2010 and December 2010 were each the largest positive values on record for those months, as was the three-month average October-December 2010. If we take a longer perspective (July-December) then 1917 was stronger than 2010, but 2010 was still the second strongest in the historical record. Using either the October-December or the longer July-December periods, the strong La Niña events on 1973 and 1975 were both ranked as weaker than the 2010 event. AMOS
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  30. For those inclined to favor the AMO (Atlantic Multidecadal Oscillation), Tamino has a nice summary opinion on it:
    "The increase in AMO from 1975 onward is because the detrending (an attempt to remove the global warming signal) is linear, but the global warming signal is nonlinear. Therefore the AMO increase since 1975 is because of global warming. Using it, without detrending the 1975-present segment separately, is exactly the problem previously described: using the effect of global warming as the cause of global warming."
    and
    "the residue of the global warming signal in the AMO data gives the visual impression of a roughly 60-year cycle -- a mistaken idea for which there's no evidence other than wishful thinking on the part of denialists."
    and finally
    "It really comes down to another lame attempt to claim that some "natural cycle" is responsible for global warming. The cycle doesn't exist, the one you think you see is the residue of global warming in N.Atlantic temperature data. If you want to remove the impact of N.Atlantic fluctuations on global temperature, detrending the post-1975 AMO is the only way to do it right.]"
    I'd read a great deal lately on the AMO as a possible source for some of the observed warming in the NH, but this is (honestly) the best explanation of the AMO I've yet read. Or at least that I've understood. Good stuff. The Yooper
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  31. Muon @ 176 "I show you peer-reviewed research that 'suggests' changes to el Nino are based on AGW; that 'confirms' that human activity can and does alter global phenomena." How does one go from taking research that "suggests" a hypothesis to "confirming" your opinion?
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  32. muoncounter, "RW1#59: "unless the amount of warming is outside the range of natural variability" That works both ways. Please tell us exactly the range of natural variability and how you obtain that figure." Good question. In general, if the trend amount is less than the amount of observed variation over the trend, it's not outside the range of natural variability.
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  33. RW1 - I think that is voodoo statistics here. Perhaps you might like to explain in detail how you would do that calculation? Tamino attempts this at Open Mind and also sees what happens if you remove the known causes of variability. Can you do better than that? and of course the way to account for it with physics is compare model outputs with only natural forcing compared to models with all forcings.
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  34. What's all this +0.3 degrees over the last 30 years nonsense anyway? Last I checked, the planet was warming at between +0.16 & +0.17 degrees per decade, which puts total warming at closer to +0.5 degrees over the past 30 years-& +0.6 degrees over the last 50 years. Given that this 30 year period has been dominated by a general *decline* in incoming solar irradiance, I really don't see how even the most committed denialist can claim that this is all part of some mystical "natural variation". After all, we didn't get that much warming even when solar irradiance was climbing during the first half of the 20th century.
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  35. scaddenp (RE: 183), "Tamino attempts this at Open Mind and also sees what happens if you remove the known causes of variability. Can you do better than that?" The techniques he uses to try to remove known causes of variability are highly speculative at best. All he's really showing is when these are removed there is a clear warming trend of about 0.3 to 0.4 C from 1979-2010, which really isn't in dispute. The problem fundamentally is the entire trend can be wiped out in just one year or so of natural variation. This makes it very hard to distinguish whether the trend is mostly random natural variation or mostly from one particular variable, such as man's CO2 emissions.
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    Response:

    [DB] Tamino is a professional time-series analyst quite versed in climate analysis.  All you're really accomplishing here is demonstrating your lack of foundation in understanding statistical trend analysis.

  36. "The problem fundamentally is the entire trend can be wiped out in just one year or so of natural variation." Yet it hasn't, RW1, so why is that? The warming trend for the past 30 years has been shown to be statistically significant-using a myriad of different tests-which disproves your entire "caused by natural variation" hypothesis. An hypothesis, I might add, which reads more like an article of faith.
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  37. No it hasnt!! Learn some statistics. Does winter wipe out a whole summer of warming? Look at the first link in open mind which looks at trend as function of start date. When you have a lot of internal variability, then you have to distinguish trends over a long period and what he does hints at the method that you use to discover how long. That is what climate is 30 years, not what happened last year. You can only "wipe" a warming trend with enough years of cold data that long term trend is zero or less. One cold - or one hot - year does not tell you about trend. Furthermore, its not as if there is any particular mystery in whether one year is hot or cold. You can predict pretty confidently that this year will be colder than last. La nina. You can also see from trends that year will be a lot warmer than similar sized la nina year from 30 year ago which what we are talking about with AGW.
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  38. Marcus (RE: 186), "Yet it hasn't, RW1, so why is that?" But it has. Look at the graph. The globally averaged temperature is already back to what it was 30 years ago in 1980. Just three years ago in 2008, the temperature was lower than it was at the beginning of the satellite record.
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    Response:

    [DB] Umm, no.  RW, you were recommended earlier to learn a bit more about statistical trend analysis; I'd advise you do so.  For your own benefit.  You are not doing well, here.

  39. RW1, do you even bother to check your claims? The average global temperature anomaly for 1980 was +0.02 degrees C above the 1979-2000 average. In 2008, the temperature was +0.1 degrees above the 1979-2000 average. Given that 2008 was (a) a La Nina year & (b) the nadir of the previous solar cycle & (c) Given that there are some pretty significant holes in the coverage of the satellite temperature measurements, I think this kind of debunks your entire premise. Of course, looking at year-to-year variability is a complete strawman anyway, what is more important are the following facts: (1) The average temperature anomaly for each decade has been *warmer* than the decade before. (2) The difference between the temperature anomaly for each decade is getting *larger*. (3) That the trend-line for warming is statistically significant. Now, if this were all down to just internal variability, then at least one, if not all, of those facts above shouldn't be the case. The question then remains. How, in the absence of a downward trend in Total Solar Irradiance, do you explain a total of +0.5 degrees of warming between 1979 & 2009?
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  40. He is just looking at March and comparing to every other month, not the annual global average. Its not even especially low.
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  41. Wow, that's Cherry Picking at its *worst* scaddenp. I mean, hasn't he heard the saying "one swallow doesn't make a Spring"-the same can be applied to climate data. The simple fact that the monthly temperatures not only bounce back, but tend to bounce higher & higher every few years indicates that all that extra heat energy is still in the system, & continues to build up.
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  42. Indeed, RW1 is doing a *mega* cherry-pick. Pick a single month from the *least* reliable source (UAH) of *satellite* data (so failing to see the warmth in the polar regions), & even then he can *barely* achieve the result he's looking for. April here in Australia was pretty well above average-especially now that the La Nina is officially finished-so I wonder if he'll compare April & May results?
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  43. "The problem fundamentally is the entire trend can be wiped out in just one year or so of natural variation." No, it can't. I think you're confused as to what a trend represents -- it's the average slope, not the temperature [anomaly] at a point in time. "In general, if the trend amount is less than the amount of observed variation over the trend, it's not outside the range of natural variability." If that were the criteria we would never be able to discern a trend in any observational series. I'd feel a whole lot better about my stock portfolio over the past 4 years...
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  44. Marcus at 18:39 PM, where are you getting the information that La-Nina is officially finished? The El-Nino Index is still in negative territory, about -1, and though it is weakening slightly, it is expected to strengthen again and remain negative well into 2012.
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  45. It must be confusing trying to use the UAH figures each month to try to determine the state-of-play of the planet. As well as desperately trying to convince yourself that because March 2011 has the same anomaly as March 1980, AGW has magically gone away, you would also be up and down, from happy to sad, like a jack-in-the-box : Most of 2010 highest since 1998 ? The globe obviously hasn't warmed since 1998. Jan 2008 lower than since the beginning of readings ? We are now in global cooling. Early 2007 showing highest anomalies since 1998 ? The globe obviously hasn't warmed since 1998. Jan 2000 lower than since the beginning of readings ? We are now in global cooling. 1998 the highest since the beginning of readings ? That's obviously not right and can be ignored, or used to state that the globe hasn't warmed since that time. Nov 1984 lowest anomaly ever (since the beginning of readings) ? We are now in global freezing.
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  46. johnd wrote : "The El-Nino Index is still in negative territory, about -1, and though it is weakening slightly, it is expected to strengthen again and remain negative well into 2012." Where are you getting your information from, concerning the prediction into 2012 ? The latest NOAA ENSO Cycle: Recent Evolution, Current Status and Predictions states : A transition to ENSO-neutral conditions is expected by June 2011
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    Moderator Response: [muoncounter] fixed link
  47. RW1#182: "if the trend amount is less than the amount of observed variation over the trend, it's not outside the range of natural variability." The question was (and still is): what exactly is that range of natural variability? Until you provide said range, together with a documented analysis of how its derived, you have no business making any such claims. scaddenp#187: "Does winter wipe out a whole summer of warming?" This appears to be an echo of prior comments.
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  48. JMurphy at 22:06 PM, I follow the JPN-FRCGC model predictions which is included amongst the range of predictions on page 27 of your linked site. Just remain aware that I referred specifically to the El-Nino Index value, not whether that value was moving in or out of the range considered neutral or not. I note that NOAA confirm on page 3 and elsewhere that as at May 2nd, La-Nina conditions are still in place.
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  49. johnd, just to be clear, please provide a link to your assertion that "[the El-Nino Index value/La-Nina' is expected to strengthen again and remain negative well into 2012.
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  50. I can't believe that someone hasn't already posted this link and picture as a response to RW1 but, just in case : Staggering Drop In Global Temperature The current temperature anomaly for March 2011 has just come in at -0.1C. That's MINUS 0.1C which is below the freezing point of water, so how can the arctic be melting? (Thanks for the previous link-fix, muoncounter - I hope you don't have to do the same again with this...)
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