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Resolving Confusion Over the Met Office Statement and Continued Global Warming

Posted on 10 January 2013 by dana1981

Recently, the British Met Office issued a prediction for global surface temperature changes over the next five years (Figure 1).

Met Office decadal prediction

Figure 1: Observed (black, from Hadley Centre, GISS and NCDC) and predicted global average annual surface temperature difference relative to 1971-2000. Previous predictions starting from June 1960, 1965, ..., 2005 are shown as white curves, with red shading representing their probable range, such that the observations are expected to lie within the shading 90% of the time. The most recent forecast (thick blue curve with thin blue curves showing range) starts from November 2012. All data are rolling annual mean values. The gap between the black and blue curves arises because the last observed value represents the period November 2011 to October 2012 whereas the first forecast period is November 2012 to October 2013.

This latest prediction anticipates a bit less global surface warming than the prediction from last year, as the Met Office explained:

"The latest decadal prediction suggests that global temperatures over the next five years are likely to be a little lower than predicted from the previous prediction issued in December 2011.

However, both versions are consistent in predicting that we will continue to see near-record levels of global temperatures in the next few years."

"...changes in ocean surface temperatures in some parts of the world over the past year are understood to have made a key contribution to the difference between the 2011 and 2012 forecasts, but other factors will also have played a role."

In other words, the Met Office anticipates that natural factors which have dampened the global surface warming over the past decade (a preponderance of La Niña events and low solar activity, for example), may continue to have an overall dampening effect over the next 5 years.

Media Confusion About Continued Global Warming

Unfortunately, the Met Office prediction has resulted in quite a few confused articles in the mainstream media.  For example, the Daily Telegraph, Daily Mail, Daily Express, Canada's National Post, the Times, and the Indian Express all incorrectly reported that the Met Office is admitting that global warming has "stalled", or some similar variant.  These headlines are in direct contradiction to the Met Office forecast, which specifically stated:

"The forecast of continued global warming is largely driven by increasing levels of greenhouse gases."

The confusion arises from the fact that the thick blue line in Figure 1 (the central Met Office prediction) does not rise very far above the previous highest global surface temperatures in 2010, 2005, and 1998.  However, by no means does this indicate that global warming has "stalled".

Underlying Human-Caused Surface Warming Continues

As noted above, the Met Office prediction and explanation of their prediction specifically state that while natural short-term influences are dampening the warming of global surface temperatures, the underlying human-caused warming trend nevertheless remains. 

This is beautifully illustrated by a video created by Skeptical Science's Kevin C, with voiceover provided by Daniel Bailey.  The video shows the statistical removal of the short-term warming and cooling influences of volcanic eruptions, solar activity, and El Niño and La Niña events from the global surface temperature record.

The video shows that the global surface temperature record provides no evidence to suggest that human-caused greenhouse warming has slowed.

The Bigger Picture - Ocean Warming

Additionally, global surface temperatures are not an adequate measure of global warming.  In fact, more than 90% of the overall warming of the planet goes into heating the oceans (Figure 2).

where is warming going

Figure 2: Components of  global warming for the period 1993 to 2003 calculated from IPCC AR4 5.2.2.3.

Nuccitelli et al. (2012) considered the warming of the oceans (both shallow and deep), land, atmosphere, and ice, and showed that global warming has not slowed in recent years despite the dampened surface warming trend (Figure 3).

Fig 1Figure 3: Land, atmosphere, and ice heating (red), 0-700 meter OHC increase (light blue), 700-2,000 meter OHC increase (dark blue).  From Nuccitelli et al. (2012).

Picking Cherries, Vintage 1998

Some of the confused media articles also made the mistake of claiming the Met Office prediction indicates a global warming "stall" from 1998 through 2017, because the average 2012—2017 surface temperatures are predicted to exceed the 1998 peak by a small margin.  This is a classic exampe of one of the 5 characteristics of scientific denialism: cherrypicking.  As Professor Myles Allen, Head of the Climate Dynamics Group at the University Of Oxford, explained to the Science Media Centre,

"Comparing the expected temperature for 2013-2017 with a single exceptionally warm year (1998), as some reports have done, is just daft.  1998 was around 0.2 degrees warmer than the 1996-2000 average, largely thanks to a massive, once-a-century El Niño event.  The IPCC predicted a warming of 0.1-0.2 degrees per decade due to human influence back in 2000.  That means the one-off impact of that El Niño event was equivalent to about 20 years of the expected background warming trend So, unsurprisingly, 20 years later, expected temperatures have risen so that an average year is now as warm as that exceptionally hot year."

In fact, even allowing this cherrypick, the global surface temperature trend since 1998 is likely one of warming, which will likely continue to be the case in 2017 even if the Met Office prediction is correct.  Warming is measured through trends, not by comparing cherrypicked individual data points.

Avoiding a False Sense of Security

Although many natural influences have acted to dampen global surface warming over the past decade, and potentially for the next 5 years if the Met Office prediction is correct, allowing this coincidence to lull us into a false sense of security would be a mistake.  Eventually the preponderance of La Niñas will end, solar activity will rise, and so forth.  If we have not reduced human greenhouse gas emissions in the meantime, we will face the harsh reality that the time wasted will force steeper and more painful emissions cuts in the future if we are to avoid dangerous climate change.

Let's get real.  Global warming is (still) happeningHumans are causing it.  If we don't do something to stop it, the consequences are going to be very bad.  So let's stop looking for distractions and excuses to delay action, and get on with solving the problem, before we run out of time.

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Comments 51 to 100 out of 120:

  1. smerby, to do so would be akin to reporting, in a mainstream news source, that "Solar Radiation Has Begun to Rise Sharply!" and not telling them that it's part of the 11-year solar cycle. Despite the decline in journalistic quality and ethics, people still view mainstream news sources as somewhat reliable. That means they have tremendous power to shape opinion, and opinion is often (but not always) the basis for action. If someone wants to know what the ten-year trend is, the information is readily available. Why does it need to presented in the mainstream news? It's not like the mainstream news is reporting the ten-year trend when it's positive. Why do you want them to report it when it's negative? The Met Office didn't even report the 15-year trend; Rose and Delingpole had to lie (that is fact, moderators) and make it appear that they did. So why do it? What's the purpose? You know the opinion of science: "climate is 30+ years." What, then, would be the reason for doing it--as I've asked you eighteen times now. I've also asked you what it means to you. I have this image of you standing with your arms folded and a petulant look on your face, saying, "I just want it that way!"
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  2. To add to CB's point, lillybutter, the surface temp record technically cannot falsify the theory of anthropogenic global warming. It can only cast doubt on the model projections. In order to falsify the theory of AGW, one would have to show that the cooling efficiency of the Earth is not affected by an increase or decrease of one of a number of atmospheric gases (H2O, CO2, CH4, etc.). That's not even remotely in question. With a very high level of confidence we can say that, no matter what the surface temp analysis says, it will be warmer with 300ppm CO2 than it will be with 100ppm CO2. What I'd like to see is an analysis of what global temp would be without the rise in CO2 and CH4. Oh, and the surface temp--esp. not just HadCRU4--is not the climate system, so rephrase the question to include OHC and global ice mass loss.
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  3. smerby@23, 25,30, and 33: This strident assertion that all you want is "the indisputable facts" has been, extremely patiently I might add, explained again and again, to you and others. What you seem to want is a simple, sound-bite-y chunk of simplistic reporting: It's that type of simplistic reporting by the MSM that has led to such confusion and tripe, being passed along as "facts." Science doesn't work that way, and no amount of desperate hand-waving will change that. The fact is, indisputably and by numerous metrics (lines of evidence), global warming *overall* has NOT stopped, and that global ~surface~ warming has only slowed down to a statistically-insignificant margin, not "stopped." Warming on the globe has not, repeat, not stopped, and that is the point of many of your respondents. We'd ~all~ like this to be simple and I guarantee you, we earth scientists would love *nothing* better than the entire AGW theory to be disproven; at this point, there are no data that shows that has happened. Insisting you want a simple, factual, and at the same time, *wrong* conclusion shouted from the rooftops isn't going to help the critical mission, that being to spread awareness that this IS an issue we ~must~ address, NOW.
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  4. CBDunkerson, BernardJ: Actually you can find such periods, for example by exploiting volcanoes. 1992-2002 using the large Pinatubo cooling at the start of the period is an example. There's another one 1974-1984, but they're pretty rare and usually depend on some known phenomena. Drawing conclusions from trends which include known uncorrected short term variations remains a meaningless exercise. Of course, you would expect 1 in 20 (40) to be significant by chance, so the problem with Smerby's argument stands even if we ignore the short term influences. This cartoon is a barometer of whether this point has been understood: Significant Finally, testing for statistical significance in the trend is the wrong test - this is an elementary statistical fallacy called the fallacy of null hypothesis rejection. You can't falsify 'ongoing warming' by checking for a trend significantly different from zero. All you can do is falsify 'no warming', which is exactly the opposite of the test Smerby wants to perform. To falsify 'ongoing warming' you have to check for a significant deviation from some predicted trend, having removed confounding factors.
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    Moderator Response: [RH] Tweaked image width (yes, I'm being anal about the page formatting again).
  5. Anyone coming in here and trying to argue about global warming on the basis of the surface temperature record has two "just the facts" to contend with. First is, as shown in Figure 2 and 3 of the OP: most (97-98%) of the action in global warming is not in surface temperatures. Second is, as noted by tobyjoyce, the ongoing radiative imabalance at top-of-atmosphere, such that energy out < energy in. Unless these are accounted for, anyone trying to claim "global warming has stopped" or has "stalled", or there's a "pause", or anything along that line has no case whatsoever.
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  6. # 49 Yes it is possible to find 10 years periods in the temperature record with statistical significant trends. In the plot (click here for large version) below I show all 10 years (120 months) trends for the period 1900-2012 for HadCrut3. The confidence (95%) region is indicated as a bluish shaded area*. When this band is not including the zero line, the trend is statiscally significant. *) Technical note: I have corrected for autocorrelation by assuming it to be constant over the period using a correction factor nu = 3.4 for all trends. I have not corrected for multiple comparisons.
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  7. Nice work SRJ. I'm matching that up against the 2-box model output: 92-02 is Pinatubo of course. 74-84 is a massive ENSO swing, so that's not unprecedented either. 64-74 is Mt Agung 55-65 is less well captured in the model but has an ENSO component. The two big swings around 1940 are interesting and probably related to the SST adjustments. The down swing is certainly the unadjusted transition from engine room temperature measurements to buckets in 1945, and should be corrected in HadCRUT4. The upswing is unaccounted for, although I have unpublished evidence (John Kennedy at Hadley has seen it) that suggests the bucket correction may be underestimated by about 1/3, which if correct would explain part of it. However even if I am right there is certainly a residual 1935-45 temperature anomaly which is not captured by any model I have seen.
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  8. Those arguing that a 10-year trend in surface temperature means anything, especially without considering the other influences on surface temperature from volcanic aerosols, the solar cycle, and El Nino/La Nina events, have completely missed the point of this post. Just as Kevin's animation shows that the warming trend over the past 16 years is the same as the previous 16 years after the other influences are removed, that conclusion also holds for the past 10 years. Readers should also be aware that it is a common denier tactic to cherry-pick time periods that are too short to say anything statistically meaningful about global warming, especially when the other short-term influences on climate are not considered. That tactic is nicely illustrated by The Escalator.
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  9. Clyde - I would recommend as a resource Google Scholar (scholar.google.com), a search engine for papers, patents, etc. Searching there for "nuccitelli et al 2012" gives a link to an open PDF, which is not surprisingly found here. There are quite often openly accessible copies of otherwise paywalled or out of print papers available from the authors or other sources; checking "all versions" for a paper is often worthwhile. Read it, look at the references and sources for the data. Perhaps then your comments will be more relevant to the contents of the paper and the figures you have questioned.
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  10. Oops...actually my comment #58 refers to the previous post by Kevin C, but really, the comment still stands as Kevin's animation does nicely address the 10-years comments raised here.
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  11. # 57 KevinC Here is the same plot for HADCRUT4 I think that the significant 10 years trends in the nineties are related to the super El Nino of 1998 rather than the Pinatubo. This plot, as well the one for HADCRUT3, shows that 10 year trend rarely are statistical significant.
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  12. Thanks again. Yes, you are right, both Pinatubo and ENSO play a part in the 90's trend. Here's the 2-box+enso model output: Red is the model, blue is GISTEMP. Data runs to the end of 2010. I use this as a crude metric to determine what is unexplained in terms of climate. As you can see the model also shows the recent flattening, which comes from the ENSO term. The 40's deviations are partly explained by the SST adjustments which GISTEMP doesn't have. The late 30's deviation is still a mystery. The deviation right at the beginning is an equilibriation artefact.
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  13. Clyde @31 and KR @59 - the link to Nuccitelli et al. (2012) in the Figure 3 caption is the free version. As I said, our OHC data comes from Levitus, which is NOAA. smerby - "facts" without context are useless, particularly in mainstream media articles where the general public does not have the expertise in the subject in question to interpret what those facts mean without the necessary context. Articles that simply say "no surface warming trend in 10 years" lack the context given in this post - for example that such 10-year periods are expected by climate models, that the planet would have cooled over those 10 years if not for the human GHG-caused warming, that 10 years is too short for a statistically significant trend, etc. etc.
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  14. The controversy over the Met Office short-term climate forecasts is also reviewed and analyzed in two well-written articles posted on The Carbon Brief. They both provide insights not included in Dana’s excellent OP. Why the Met Office’s revised forecast still doesn’t show global warming has stopped by Roz Pidcock, The Carbon Brief, Jam 9, 2013 That Met Office media controversy in context by Ros Donald, The Carbon Brief, Jan 10, 2013
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  15. smerby - "Facts" without context are perhaps better termed "Factoids" - a piece of information rather smaller than a fact, as in something (like 10 year trends) presented without sufficient background to correctly interpret. dana1981 - Quite right about the link; I had only looked at what was linked through the figure itself, which is the full version of the graph. Although it's still quite worthwhile to point folks to Google Scholar.
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  16. Has anyone else noticed how smoothly the chants of "Global Warming is not Happening!" have been replaced by: "Global Warming was Happening, even when we said it wasn't, but now it isn't any more!".
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  17. "Has anyone else noticed how smoothly the chants of "Global Warming is not Happening!" have been replaced by: "Global Warming was Happening, even when we said it wasn't, but now it isn't any more!" I sure have: it's been nearly instantaneous in the denialoshere, and I take that as good news. As reality and observable data intervene in their narrative, the fake "skeptics" are back-peddling like a Mississippi paddle boat to avoid a cataract. Back when there *was* water in the Mississippi....;(
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  18. I think what is more telling is how people who really don't understand (see here) latch onto the "no warming since" meme and repeat it. They're all so very eager for it to not be a problem, rather than (God forbid) own up to it, address it, make sacrifices, and fix it. If these people had been around in [insert time of historical crisis here] we'd all be [insert bad outcome here from ignoring what can now be seen in hindsight to have been very, very bad].
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  19. Agreed, Sphaerica, and what else is telling? Ever since smerby has been--educated--this is what we've heard . All in all, facts will win the day, but I fear it truly will be too late to stop the worst of what's to come.
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  20. SRJ, in that case there is clearly only one 'logical' conclusion... Global warming is intermittent... and caused by volcanoes. :]
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  21. Nice to see a youtube post. Have thought for a long time that sks should set up a channel (not under John Cooks name) and post a ~monthly vid (would much prefer a quality monthly vid than poorer quality weekly vid). I think alot of my friends are interested in the science of climate change to watch a 10min sks vid every month, but not interested enough to become a regular sks (or realclimate or CSIRO etc) reader
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  22. Question here, based on the global surface temperature record since the late 1880s, could the current flat line we are in continue for the next 15-20 years before warming resumes. If so, would that not buy us time to develop affordable alternative energy sources?
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  23. @smerby There is more to global warming that global surface temperatures, there is also the oceans, which have continued to warm. The oceans have a much greater heat capacity than the land, so if the land doesn't warm but the oceans do, then no time has been bought at all. Secondly, trends with cherry picked start dates are pretty meaningless, they are not even statistically significant evidence that surface warming has actually slowed. There is a very good chance you are just seeing noise masking the underlying warming.
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  24. Not feeling like responding to my questions, smerby? Ok. There is no "buying time." Global warming, as has been noted . . . and noted . . . and noted, has not stopped. The ocean heat content trend has shown no hiatus period, and it represents 92-3% of the global energy anomaly. That energy will return to the surface eventually, as it must. The time to do something was always "now." Why should we wait for a few lower-trend years? Develop alternative energy now. Cut energy use now. Buy simple when possible. Buy local when possible. Save the energy for things that have lasting value.
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  25. smerby, We're not in a flat line. That's a denial fantasy that has been debunked repeatedly. Look here.
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  26. 72, smerby, Also note that every bit of carbon we add to the atmosphere is like turning the thermostat up -- but it's broken, so it can't be turned down. If you turn your thermostat up to 100 degrees and then break it, your house won't jump up to 100 degrees in minutes. If it starts to warm and you turn some fans on to make it seem cool, circulating the air better around the house, that may mask the problem but it's not going to change anything in the long run. Your house is going up to 100 degrees and you can't stop it unless you fix the thermostat (and in this case there is no possible way to fix the thermostat -- there is no possible way to extract the CO2 from the atmosphere once it is there). Any supposed "slow down" in global warming isn't because these years of CO2 emissions are somehow less powerful than other years. It just means that other, impermanent factors are obscuring the effects of CO2 -- temporarily. So, if a quiet sun, Chinese aerosols, and an unusual series of La Niña events minimize warming, and then all of those factors go away, or if those factors never existed to begin with, it doesn't matter. The planet will still reach roughly the same temperature in roughly the same amount of time. So this doesn't buy us time. On the contrary, it lets deniers pretend that they can ignore the problem, wasting precious time that is turning a solvable, manageable problem into an "oh-no-oh-my-God-oh-shoot-what-are-we-going-to-do" panic, because people are going to weight until it's too late.
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  27. Clyde@31: Well, if the comment was behind a paywall (others have pointed out how to get around that), then the reply is too, so I presume that you had not read the reply, either. Posting a link to a paper/reply that you haven't read, presenting it as rebuttal to another paper/comment that you haven't read strikes me as rather odd behavior. As for wanting the source of the data in the figure, then you should have asked that to begin with instead of wasting people's time with ill-formed questions. Unless, of course, that is your goal.
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  28. To extend Sphaerica's house analogy, the deniers are standing next to the fridge, and every time the door opens and a bit of cool air spills out, they say "see? The house has stopped warming!". In spite of the fact that the fridge is simply moving energy from the air inside the fridge to the air outside the fridge (back coils) - much as ENSO mostly just shifts heat around from one part (the atmosphere) to other parts of the globe (oceans).
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  29. Actually there's the core of an interesting question in Smerby's #72. Let me pose it more precisely: Based on our current understanding of the temperature record, what would it take to keep temperatures within 0.05C of the current decadal average for another 15 years? Now the answer should be obvious. We would need either: a) A series of strong volcanic eruptions, or b) A grand solar minimum and a rather greater corresponding change in background than is reflected by the current consensus(1), or c) An increasingly negative ENSO state, or d) The climate to start behaving in a way rather different to the way it has behaved for the last 35 years (simple model) or 130 years (forcing model). A solar minimum doesn't look like it is up to the job, and we don't have a means to forecast volcanoes, so we're stuck with rolling the dice on those or hoping for a drastic change - either for ENSO to start behaving in a way it hasn't before, or for the relationship between temperature and forcing+ENSO to break down. Of course there's no reason it should break in a way that helps us. My turn for an analogy: That seems to me like walking off a building and hoping for a change in the law of gravity before you hit the ground. (1) You can still find a lot of old TSI graphs with very large changes between the Maunder minimum and today. These do not reflect the current consensus.
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  30. Good points all. Image and video hosting by TinyPic Image and video hosting by TinyPic Image and video hosting by TinyPic I see leveling off trends over the past 10 years with global surface temperatures, sea surface temperatures, and OHC down to 700 m. OHC down to 2000 m has not leveled off and continues to warm so that is where the global warming is. Records of global surface temps and sea surface temps going back to the late 1800s support the current leveling off trend and the records also show that the leveling off should last for another 20 years. I know the current trend can be attributed to noise but is 1/3 of a climate cycle and could continue the next 20 years. I understand that each leveling off period is warmer than the past and could be attributed to increased C02. These are periods that we can bear down on finding alternative energy sources without stressing people.
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    Moderator Response: [RH] Fixed image widths.
  31. smerby.... The problem is, increasing levels of CO2 represent increasing radiative forcing. Regardless of the signal you see in the surface temperature data, it's the change in forcing that is the problem. If there is no reduction in radiative forcing, that just means when the surface temperature does return to the long term trend, it's going to do so more abruptly.
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  32. smerby, first let me say thanks for returning to the discussion, with what appears to be an open(ed) mind: It does appear that you are trying to get past prior denialist fake talking points. That said, what you still call "leveling off" to me, and statistically, isn't so much a 'leveling' but a tendency toward a less steep slope.' It's not just a semantic point, but rather a more precise science-language-based way of interpreting the data. "Leveling" would be a slope of near zero, and that is not what we're seeing, especially overall, if we examine all sinks of downwelling radiative energy. I think I can fairly speak for most, if not all, climate scientists and those who are deeply and constructively engaged in the field: No one is trying to 'scare' people, per se, but we have reached a point--again, supported by *many* lines of evidence--where we simply do NOT have any more time to wriggle about, till we know 100% of what can be known. Sir Paul Nurse's takedown of Delingpole comes to mind, inasmuch as a consensus of the globes experts have arrived at essentially the same position, that the confidence level of the "A" in GW being real to a factor of 2 sigma. Yes, we need to keep level heads, and we all here are trying; however, at the *very* same moment, we are also deeply troubled by what we see, both in the progression of what we pretty well knew 20 years ago, and the damage that is being caused by the denialati, watts among one of the worst. Everything, and I mean ~everything~ that can be brought to bear upon this issue---solar, wave energy, geothermal, efficiency (conservation witha capital C, foremost), sustainable farming, shipping, and distribution factors, the list is way too long to continue here. the facts we need are here, they are vetted by somewhere north of 14 *thousand* scientists and organizations, and they all point to the same issue. We are running out of time. By all means, keep asking questions, and I can guarantee you will find an answer here at SkS, but also, please consider stopping the spread of FUD, in any way that you *might* be involved in: The stakes of inaction are just getting too high for that. It's that frustration that you may see sometimes bubble to "our" surface. If we don't, the stress the global population WILL experience, dealing with a 2C to 4C rise in surface temps, will go ~waaaay~ beyond any stress you currently sense.
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  33. smerby, can you give some evidence for these assertions: "Records of global surface temps and sea surface temps going back to the late 1800s support the current leveling off trend and the records also show that the leveling off should last for another 20 years. I know the current trend can be attributed to noise but is 1/3 of a climate cycle and could continue the next 20 years." Did you get that from the scientific literature or some blog site?
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  34. smerby @80 writes:
    "[T]he records also show that the leveling off should last for another 20 years."
    The record shows nothing of the sort. I have just finished an analysis of how successfully you can predict future temperatures from trends of a given length. As it happened, for a ten year prediction, a 16 year trend performed significantly worse than simply adding 0.085 C to the current month's temperature. That makes the 16 year trend a very poor predictor of future temperatures. The best prediction from linear trends is obtained by adding 0.046 C (the mean under projection) to the 24 year trend projection. That yields a projection on HadCRUT4 data for 2022 of 0.744 +/- 0.391 C anomaly relative to 1961-1990; and approximately a four in five chance of exceeding the current consecutive 12 month record. Far better than any prediction from recent trends, however, is a prediction from physics. Here for example, is a comparison of the prediction from 16 year trends and that from CO2 forcing alone: As you can see, prediction from trends performs far worse than prediction from physics, even when you only include one (albeit dominant over the long term) forcing. When you include all forcings plus ENSO, as Kevin C does, there is not contest between the predictions made from physics, and those made from trends only: Yet you want to predict a 36 year pause in global warming from a cherry picked 16 year trend in contradiction to the physics? As I said, your claim has no basis.
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  35. Rob @81 I wonder whether people like smerby, don't appreciate the full extent of the sources of evidence for climate sensitivity. In other words smerby might be assuming (sorry if I'm putting words into your mouth, smerby) that future temperature rise projections come from a climate sensitivity value that is solely determined from the temperature record for the last 30 years and therefore such projections assume that there are no long term (multi-decadal) oscillations. (Conversely, of course, smerby would then believe that if multi-decadal oscillations did exist and the last 30 years was on an up-swing, then future temperature rise projections would be over-estimated). In actual fact only a very few of the methods of determining climate sensitivity use the recent temperature record, and so the supposition of a multi-decadal oscillation does not alter the long term trend.
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  36. Thanks for the feedback. That graph I put up with global surface temps and sst going back to the 1880s clearly shows repeating ~30 year trends. Based on that graph, the leveling off of surface temperatures for the past 10 years falls right into step with these repeating trends. Could this trend continue for the next 20 years, I think it could. What would knock this repeating cycle of global surface temperatures off track?
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  37. smerby @86, there are have been at most 2 cycles of that pattern since 1880. That is far to few repetitions to infer a regular cycle. If you look at either HadCRUT or BEST prior to 1880, the 60 year pattern breaks down and is not in evidence. Further, it is highly dubious that it is in evidence prior to that period in paleodata. Hence the inference that it is not only a regular cycle, but strong enough to counter global warming in the medium terms is completely unsupported.
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  38. Smerby: Look a bit further back to 1850, and then look at this graph. (Or don't, the site is down, but here is the link for when it is back up.) http://data.giss.nasa.gov/modelforce/strataer/. Alternative version: The dip from 1880-1900 is not part of a cycle - it is the result of a series of major volcanic eruptions. Once you take out this effect the bulk of the cycle vanishes - it's mostly a coincidence.
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  39. global surface temps and sst going back to the 1880s clearly shows repeating ~30 year trends.
    smerby, alarm bells ring out when I see statements like these. It sounds like you're using that unreliable statistical tool, the eyecrometer. Do you understand the methods required to correctly determine the existence of cyclicity in a dataset? And the tests required to evaluate significance of such a signal. Have you considered variations in forcings (volcanic, aerosol, increasing ghgs), which can create the illusion of cyclicity? And how to test this? And why are your so-called 'troughs' - not that there is even a statistically significant change in the recent warming rate - getting rapidly warmer over time? I would suggest you can't rely on your eyecrometer to tell you the "truth". In science, there are better methods...
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  40. All, thanks again for the feedback, I really appreciate it. I hear you skywatcher and I agree that the eye test can be misleading. Some graphs do pass the eyeball test and I think the surface temp graph that I posted shows reliable and repeating trends of ~30 years. I have looked at the 12 month, 36 month, and 5 year mean versions of this graph to try to dampen out short term forcings and it pretty much shows the same trends. The overall time scale of these trends may not be long enough for a regular cycle as Tom pointed out and the early cooling part of the graph was influenced by Krakatoa as Kevin indicated, but it is interesting that the trends are ~30 years. These are roughly the same time frame as climate cycles. Why is 30 years decided as a climate cycle in the first place, why not 60 year cycles for normals; puzzled by this. The length of these global surface trends are roughly the same as the length of the trends of the PDO and AMO, which can influence global surface temperatures. The global surface temperature trends are more in step with the PDO rather than the AMO. I think this makes sense given the vastness of the Pacific Ocean. I look at these cooling and warming trends of the oceans as baffles and accelerators of global surface temperatures. Against the backdrop of global warming, they make for more of a step function rise in temperatures as opposed to a continuous cataclysmic rise in surface temperatures. What do you all think?
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    Moderator Response: [DB] Actually, the WMO defines climate as periods of time 30 or more years in length. A discussion of how this was determined can be found here. For discussions on the PDO, see here.
  41. Smerby, you keep returning to your eyeball as a reliable identifier of some kind of "cycle", but you are as yet providing insufficient evidenciary backup for this claim. [BTW, you can refer to such work as Santer et al for why you need 20-30 years for determination fo a trend in climate.] So here is one simple question for you: Q: Is there a statistically significant change in the warming trend over the past decade? If you think there is, please show your working. Eyecrometer results are not acceptable. My thinking is in line withKevin C's video above, and the final two figures of Tamino's post - that the underlying trend has not actually changed over the past decade. Global temperatures are where you would have expected, had you plotted a graph in 2000, estimating the subsequent 12 years. Skeptics often claim that somehow there's cooling, large overprinted cycles or other changes that are manifesting themselves just now or shortly in the future. You claimed that temperatures have "flat-lined", yet is there any actual evidence for this? I contend that there is not. I also contend that you are confusing noise with signal.
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  42. smerby... First off, I greatly appreciate you sticking around to discuss the subject. You're clearly interested, even though sometimes it can be tough to push through and get all the answers you want without getting frustrated. One suggestion I would offer is to remember, this is all about the greenhouse effect and the change in radiative forcing on the climate system. All the elements we're discussing, including surface temperature, are responses to that change in forcing. What I think I see your questions possibly alluding to (correct me if I'm wrong), is whether there is another explanation for global warming. Is it something internally cyclical about the climate system (i.e., PDO, etc.). And what I would have to remind you of is, the radiative properties of GHG's are well understood. What would be utterly amazing would be if the changes in GHG concentrations in the atmosphere did not act to change surface temperatures.
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  43. Smerby says: "Some graphs do pass the eyeball test and I think the surface temp graph that I posted shows reliable and repeating trends of ~30 years." THere is a serious problem with this statement. The eyeball is not a test, can not substitute for a real statistical analysis. There is a variety of true statistical methods to determine if a cycle is a present in a data set. I'm sure Dikran can weigh in on that; Tamino has posts dedicated to the subject. One can assert that a cycle is present only after subjecting the data to these tests. Saying "I think a cycle shows" without being able to refer to any analysis is dangerously close to being full of it. It is nowhere near a skeptical attitude. Cycles are extremely easy to mistake for stochastic fluctuations.
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  44. Phillipe Chantreau @93:
    "Cycles are extremely easy to mistake for stochastic fluctuations."
    I suspect you mean that around the other way, although no doubt both ways are true when the data is less than a few "cycle" lengths in duration.
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  45. smerby As others have said, testing by eye is extremely unreliable. We have evolved such that our brain tries very hard to detect patterns in what we see (e.g. so that we can detect ambush predators that are hiding in cover). This is one reason that optical illusions can be so convincing. This is why we should use objective statistical methods to test out hypotheses. However, don't stop there, the next step is physics. A good physical theory is more convincing that an observed correlation, as it allows you to go into the causal mechanisms. For example, there are good physical reasons that can explain the apparent cyclical changes in climate sine 1880, based on observed changes in the forcings. This means that if for the changes to be due to a real cycle, then much of what we know about atmospheric and radiative physics must be wrong. So do you have a physical mechanism to explain the 30 year cycles and an explanation of where our knowledge of physics is wrong? Lastly, scientific method is based on the idea of self-skepticism - if you want to promulgate an hypothesis, the onus is on you to test it first. In this case, if the hypothesis of climate change being cyclical is based purely on the observations, then you need to show the evidence for those cycles is statistically significant (i.e. that the observations would be unlikely under AGW).
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  46. "Eventually the preponderance of La Niñas will end, solar activity will rise, and so forth." Will this happen naturally or by increased greenhouse emissions?
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  47. Yes Tom, that's what I meant.
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  48. snafu @96 - naturally. Solar activity has nothing to do with GHGs, and the link between GHGs and ENSO is unclear, but by definition it's cyclical and will eventually transition to more El Niños.
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  49. smerby: What sort of cycles does your eyecrometer identify in the following sequence of (x,y) data points, and what y-value do you predict for x=11? (1,2) (2,7) (3,1) (4,8) (5,2) (6,8) (7,1) (8,8) (9,2) (10,8) Hint: it's not 1 or 2. Can you predict the next value of y to within 1, using cycles? The origin of the sequence is well-known and understood, so it is exactly predictable with a correct model. Answer is in Ray Ladbury's recent comment over at RealClimate, where I have gratuitously stolen the example.
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  50. Smerby. Philippe Chantreau and Dikran Marsupial have both told you how visual assessment is not a reliable way to "test". Lest you have any lingering doubt about this, I will offer some empirical evidence: (Be sure to follow the link to the source page, and check out the first link there, titled "Here comes another seizure"...) I apologise profusely for the liberal inclusion of the above images, but it seems that too many people are blithely unaware of just how much our "lying" eyes mislead our minds. If ever someone thinks that they can just scan a graph and objectively analyse its data and particularly the trends described therein, they should have another look above. Most especially if they have no expert or other professional familiarity with the mathematical structure of the data they choose to "test" with their eyes...
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