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Thursday, February 25, 2016

Global surface warming continues without pause contrary to denier claims

Sou | 9:02 AM Go to the first of 46 comments. Add a comment

There's another new paper out in Nature Climate Change today that discusses the recent trends on global surface temperature. It's by a rash of notable authors: John C. Fyfe, Gerald A. Meehl, Matthew H. England, Michael E. Mann, Benjamin D. Santer, Gregory M. Flato, Ed Hawkins, Nathan P. Gillett, Shang-Ping Xie, Yu Kosaka, Neil C. Swart. Anthony Watts heralded the paper (archived here), which is unusual because he normally scoffs at the findings of most of these authors. He referred to an article in the Examiner newspaper, which claims that this paper contradicted "another study last June" that stated that the "the hiatus was just an artifact that “vanishes when biases in temperature data are corrected.”

Well it doesn't contradict it. Needless to say Anthony and the Examiner was comparing apples and oranges.

The new paper, Fyfe16, discussed the reality of the slowdown. There was no "hiatus" or stopping of global warming, contrary to Anthony Watts' headline. The rise in global surface temperatures slowed down earlier this century compared to the rate of rise from the mid-1970s to the late 1990s. As Jeff Tollefson of Nature wrote about the lead author: "Fyfe uses the term “slowdown” rather than “hiatus” and stresses that it does not in any way undermine global-warming theory."

I'll point out that other papers that have looked at change points in the longer term trend detected no change since the beginning of the 1970s. So the slowdown in the early 21st century wasn't enough to change the longer term trend.

The paper begins by stating:

A large body of scientific evidence — amassed before and since the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5)1 — indicates that the so-called surface warming slowdown, also sometimes referred to in the literature as the hiatus, was due to the combined effects of internal decadal variability and natural forcing (volcanic and solar) superimposed on human-caused warming2. Given the intense political and public scrutiny that global climate change now receives, it has been imperative for scientists to provide a timely explanation of the warming slowdown, and to place it in the context of ongoing anthropogenic warming. Despite recently voiced concerns, we believe this has largely been accomplished.
From where I sit, there's no conflict between the scientific papers on the subject, whether it's Karl15, Trenberth15 or Fyfe16. It's being presented as a controversy by some of the authors and journals, but the evidence presented by all of them is consistent. All that's happened is that some authors are emphasising the fact that global warming hasn't stopped, while others are emphasising the fact that there was a relatively short period recently when global surface temperatures didn't go up as quickly as they did in the late twentieth century. For example this new paper opens with the provocative statement:
It has been claimed that the early-2000s global warming slowdown or hiatus, characterized by a reduced rate of global surface warming, has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims.

It's a tempest in a teacup. All this sort of silly posturing does is confuse the public. It also gives science deniers an opportunity to gloat and show their inconsistent cherry-picking approach to climate science.

FWIW, I disagree with the authors of Fyfe16 when they talk of "overstated". There have been a number of people who have overstated the slowdown in warming, almost all of whom have been science deniers. Many of these "overstaters" have falsely claimed (and continue to claim) that global warming has stopped. If that's not "overstating" then I don't know what is. As for there being a "sound scientific basis", unless the authors of Fyfe16 are talking about science deniers, then I'm not aware of anyone who disputes the fact there was a short term slowdown in surface warming, or the scientific explanations. As the authors of Fyfe16 show in their paper, the recent "slowdown" (which now seems to have stopped) looks different depending on when you pick the start and end dates, and on what period you compare it to.

To elucidate, there are a number of main points relating to recent global surface temperatures:
  • Global warming continues. It has not stopped or paused or hiatused.
  • The global mean surface temperature didn't rise as quickly early this century, compared to the rate of rise from the 1970s to the late 1990s.
  • There was a wider than expected gap between climate model projections and global mean surface temperature from the time that the forcings were estimated (2006 onwards) to around 2013). Climate models underestimated the negative forcing from volcanic aerosols and overestimated the positive forcing from solar radiation.
  • When climate models are populated with the observed forcings, then models match observations
  • Science deniers beat up the slowdown and paint it as "global warming stopped", when it didn't and hasn't, aka seeps and scams.
  • There is no observed slowing or stopping of the heat being accumulated in the oceans, where about 93% of the heat is going.
Here is the Rahmstorf chart (again) updated from Mann15, showing how there's no difference to speak of between models and observations once the correct forcings are plugged into the models:

Figure 1 | Global mean surface temperature and CMIP5. The CMIP5 multi-model mean has been updated with recent forcings and GISTemp data includes 2015 observations. Source: Stefan Rahmstorf, updated from Mann15 article in Nature's Scientific Reports.

So what does this new paper add to the understanding of global warming? Well, apart from reviewing some of the literature, the authors did something similar to what Risbey et al did in 2014. They ran a moving window over the global mean surface temperatures and compared it to models. Below is how I portrayed what Risbey2014 showed. As I said at the time, the graphic isn't meant to be accurate, it's indicative of their method:

Figure 2 | Conceptual visualiation of the sliding 15-year "window" in Risbey15. Source: HotWhopper July 2014

In the case of Fyfe16, the authors wrote how they used different sized windows:
To illustrate such issues, and to place the slowdown in the context of longer term trends and variability, we compute overlapping trends using 15-year, 30-year and 50-year windows starting in 1900. Using overlapping windows to characterize the slowdown is preferable to the practise of defining the slowdown based on arbitrary start and end dates (for example, refs 4, 8 and 9). Figure 2a–d compares observed overlapping trends against a measure of model uncertainty in simulated overlapping 15-year trends.
In all three observational datasets the most recent 15-year trend (ending in 2014) is lower than both the latest 30-year and 50-year trends. This divergence occurs at a time of rapid increase in greenhouse gases (GHGs)1. A warming slowdown is thus clear in observations; it is also clear that it has been a ‘slowdown’, not a ‘stop’. The slowdown was more pronounced in earlier observational datasets, and in studies based on them. Note also that the most recent observed 15-year trend is lower than the majority of simulated trends; common peaks in the modelled and observed overlapping trends centred around 2000 reflect similar recovery from the Pinatubo eruption in 1991. 

The  Fyfe16 authors also showed how internal variability was responsible for some of the slowdown. In particular, this was a time when the Interdecadal Pacific Oscillation (IPO) was in a cool phase. The IPO is similar to the PDO (Pacific Decadal Oscillation), but covers a bigger area of the Pacific. When it's in its cool phase, "cool" La Ninas are more pronounced than El Ninos. The authors wrote:
A different perspective on the role of internal variability is obtained through the analysis of the individual models and realizations comprising the MME. In 10 out of 262 ensemble members, the simulations and observations had the same negative phase of the IPO during the slowdown period — that is, there was a fortuitous ‘lining up’ of internal decadal variability in the observed climate system and the 10 simulations15,16. These 10 ensemble members captured the muted early-twenty-first-century warming, thus illustrating the role of internal variability in the slowdown. 
Again, this is not dissimilar to the findings in Risbey2014, in which the authors compared models where ENSO events lined up with the timing of ENSO events in the real world. Also the perspective piece by Kevin Trenberth that I wrote about some time ago.

In another part of the Fyfe16 paper, the authors refer to the main "hiatus" period in global warming, which occurred from the 1950s to the 1970s. They wrote:
During this period, increased cooling from anthropogenic sulfate aerosols roughly offset the warming from increasing GHGs (which were markedly lower than today). This offsetting contributed to an approximately constant GMST. Ice-core sulfate data from Greenland support this interpretation of GMST behaviour in the 1950s to 1970s, and provide compelling evidence of large temporal increases in atmospheric loadings of anthropogenic sulfate aerosols. The IPO was another contributory factor to the big hiatus13.

In Cahill15, the change point analysis paper, the authors found trend changes illustrated in the chart below. You can see where the only "hiatus" was since 1920. The most recent "slowdown" doesn't make the cut:

Figure 3 | Overlaid on the raw data are the mean curves predicted by the three CP model. The grey time intervals display the total range of the 95% confidence limits for each CP. The average rates of rise per decade for the three latter periods are 0.13 ± 0.04 °C, −0.03 ± 0.04 °C and 0.17 ± 0.03 °C for HadCRUT, 0.14 ± 0.03 °C, −0.01 ± 0.04 °C and 0.15 ± 0.02 °C for NOAA, 0.15 ± 0.05 °C, −0.03 ± 0.04 °C and 0.18 ± 0.03 °C for Cowtan and Way and 0.14 ± 0.04 °C, −0.01 ± 0.04 °C and 0.16 ± 0.02 °C for GISTEMP. Source: Cahill15

There were a few other points made in the new paper. I'll just comment on one more of them. The authors wrote:
The last notable decadal slowdown during the modern era occurred during the big hiatus. The recent decadal slowdown, on the other hand, is unique in having occurred during a time of strongly increasing anthropogenic radiative forcing of the climate system. 
 It might have been "unique" so far, but that's probably because it's only in recent decades that there has been a "time of strongly increasing anthropogenic radiative forcing". It's probably going to happen again when the IPO is in a cool phase again in the future.

Look, I think this is a useful paper from a scientific perspective. From the perspective of informing the public, I would have preferred the authors were more constructive rather than making it appear there are disputes in scientific circles when there aren't. Deniers aren't going to read the paper. They aren't going to care that there was no change in the long term trend. They aren't going to care that the models differed from observations because the estimated forcings were wrong. All they are going to do is point to the paper falsely claiming it is "evidence" that scientists disagree, when on these issues there would be very little disagreement (if any) among climate scientists. Or they'll do as Anthony Watts did, and point to the paper claiming there was a "hiatus" or stopping of global warming, when there isn't and hasn't been.

From the WUWT comments

Francisco did at least read the fine print:
February 24, 2016 at 9:29 am
I find it interesting that the caveat/excuse/party line is always given and cannot just refute the scam: “Fyfe uses the term “slowdown” rather than “hiatus” and stresses that it does not in any way undermine global-warming theory.”

gymnosperm picked up on the fine print too, though he or she doesn't like it:
February 24, 2016 at 9:35 am
researchers have found that climate models underestimated the cooling effect of volcanic eruption and overestimated the heating from solar radiation at the beginning of the twenty-first century4. Other researchers are investigating variability in the Pacific Ocean
Still floundering around looking for excuses. When will they get their thick heads around the reality that CO2 radiative functions need to be knocked back at least 50% in the models? When will they graduate from their high school conception of CO2 physics? 

On the other hand, Tom Halla wrongly thinks that Karl15 is "wrong". It's not wrong;
February 24, 2016 at 9:37 am
So Karl et al is wrong even after altering buoy’s to match ship cooling water intakes? I would think the real probem is reconciling Karl with RSS and UAH. 

I think that Flaxdoctor is the first to notice Professor Mann among the authors:
February 24, 2016 at 9:56 am
Check out the list of authors. It includes one Michael E (Piltdown) Mann. Has he abandoned ‘The Cause’, or is he up to something devious yet again?

Jpatrick thinks there is some sort of disconnect. There's not. January was the hottest January on record. 2015 was the hottest year on record.
February 24, 2016 at 9:59 am
A couple days ago I just finished reading how January 2016 was the hottest EVER! The disconnect just amazes me. Meanwhile, I wonder if Lake Superior is getting ready to freeze over again. 

Robert Doyle doesn't know that there was no slowdown in ocean heating, and water expands when it gets hot. (Ice melts in the heat, too.)
February 24, 2016 at 9:59 am
So, Climate Central took the opportunity to go “wall to wall” reporting dramatic sea level rise. It was picked up everywhere! New York City and Washington, DC were again under water. Oh, the humanity.
Tell us, the unwashed how the acceleration happened during the “pause”? Maybe, could it be that, sea levels are not correlated to CO2?
Oh my! 

A couple more people were befuddled by the authors, and undoubtedly befuddled by the paper. mpcraig wrote:
February 24, 2016 at 10:00 am
I just looked at the authors of that study. Say what??

Travis Casey
February 24, 2016 at 10:20 am
That really is a riddle to me. Authors:
John C. Fyfe, Gerald A. Meehl, Matthew H. England, Michael E. Mann, Benjamin D. Santer, Gregory M. Flato, Ed Hawkins, Nathan P. Gillett, Shang-Ping Xie, Yu Kosaka & Neil C. Swart 

dbstealey doesn't care what this or any scientific paper says. He doesn't care that 2005, 2010, 2014 and 2015 were all the hottest years on record at the time. He'll continue his disinformation campaign claiming global warming has stopped and accuse all the world's climate scientists of belonging to a cult.
February 24, 2016 at 11:09 am
This is hair-splitting: ‘Pause’, ‘hiatus’, ‘plateau’, etc., etc.
Fact: global warming stopped many years ago. Thus, the endless parsing, hair-splitting, and refusal to face reality by the climate alarmist cult.

jjs claims that Obama (and every US President since at least Lyndon Johnson) wants to have to deal with the biggest problem facing humanity, and falsely accused NOAA scientists of fraud:
February 24, 2016 at 11:02 am
Thomas Karl, director of NOAA’s National Centers for Environmental Information – this man did not get to the level of director without towing the company line, no matter the truth. He provided the customer with what they want. NOAA’s company line is determined by who their biggest customer/boss is and that be the Obama administration.
Only a fool would believe anything that comes out of government at the Federal level. Sad but true at this point in our nation.

References and further reading

John C. Fyfe, Gerald A. Meehl, Matthew H. England, Michael E. Mann, Benjamin D. Santer, Gregory M. Flato, Ed Hawkins, Nathan P. Gillett, Shang-Ping Xie, Yu Kosaka, Neil C. Swart. "Making sense of the early-2000s warming slowdown." Nature Climate Change 6, 224–228 (2016) doi:10.1038/nclimate2938

Mann, Michael E., Stefan Rahmstorf, Byron A. Steinman, Martin Tingley, and Sonya K. Miller. "The Likelihood of Recent Record Warmth." Scientific reports 6 (2016). doi: 10.1038/srep19831 (open access)

Trenberth, Kevin E. "Has there been a hiatus?", Science 14 August 2015: Vol. 349 no. 6249 pp. 691-692 DOI: 10.1126/science.aac9225

Karl, Thomas R., Anthony Arguez, Boyin Huang, Jay H. Lawrimore, James R. McMahon, Matthew J. Menne, Thomas C. Peterson, Russell S. Vose, and Huai-Min Zhang. "Possible artifacts of data biases in the recent global surface warming hiatus." Science 348, no. 6242 (2015): 1469-1472. DOI: 10.1126/science.aaa5632

Lewandowsky, Stephan, James S. Risbey, and Naomi Oreskes. "The “pause” in global warming: Turning a routine fluctuation into a problem for science." Bulletin of the American Meteorological Society 2015 (2015). doi: (open access)

Lewandowsky, Stephan, James S. Risbey, and Naomi Oreskes. "On the definition and identifiability of the alleged “hiatus” in global warming." Scientific reports 5 (2015). doi:10.1038/srep16784 (open access)

Niamh Cahill, Stefan Rahmstorf and Andrew C Parnell. "Change points of global temperature". 2015 Environ. Res. Lett. 10 084002. doi:10.1088/1748-9326/10/8/084002 (open access)

Grant Foster and John Abraham. "Lack of evidence for a slowdown in global temperature." US CLIVAR Variations • Summer 2015 • Vol. 13, No. 3 (open access)

Fyfe, John C., Nathan P. Gillett, and Francis W. Zwiers. "Overestimated global warming over the past 20 years." Nature Climate Change 3, no. 9 (2013): 767-769.  doi:10.1038/nclimate1972 (pdf here)

From the HotWhopper archives


  1. I'm not aware of anyone who disputes the fact there was a short term slowdown in surface warming

    I dispute that there was a short term *slowdown* in surface warming. Contrary to the real slowdown halfway the 20th century (1940 to 1970), there was no statistically significant change in the recent trend. I do not know of another way to translate the term "slowdown" in scientific terms.

    If we have a value A between 1 and 5 and
    a value B in the range of 2 to 6,
    scientists normally do not claim that A is smaller than B, but that we do not know whether A is smaller than B.

    I did not read the article yet, but if Fyfe et al. want to claim that there was a model discrepancy, then that is a *discrepancy* and not a "slowdown". I hope they did not confuse the model spread with the model uncertainty. The uncertainty is probably twice as large as the spread.

    Gavin Smith comments on Twitter are good.

    1. Thanks Victor. I agree with you. Cahill15 and others demonstrated there was not change in trend. I was trying to be accommodating of the Fyfe16 authors and being, perhaps, overly generous.

      The paper itself seems mostly fine, except for some of the provocative statements that are counterproductive (IMO). Also it's late to the party. It doesn't add anything new that I can see, it leaves out important stuff like Cahill15, and the way it's written it gives ammunition to deniers.

      I'm sure that wasn't what was intended.

      In the future, if scientists want to be controversial, I'd be happy for them to run their paper by me first to make sure it can't be abused or misused by deniers :)

    2. Okay, but that couldn't really be the reason to do it. Because climate revisionists will abuse/misuse everything - it is a given.

      Speak out. Expose.

  2. Thanks,Sou. This is all being parrotted at tallbloke at the moment, so you've obviated the need for me to spend any time in that snake pit. Funny how the likes of Santer and Mann suddenly become worthy scientists. Cognitive dissonance galore. It's so reminiscent of those Donald trump rallies,where Mexican Americans cheer heartily at a man saying that Mexicans are criminals.

    1. Many years after choosing the physical sciences over other fields, I never thought I'd be as familiar with cognitive dissonance, motivated reasoning, confirmation bias, the Dunning-Kruger effect and the entire menagerie of logical fallacies as I am now.

      I can't say it's been anything I'd have wished for, given a choice.

  3. Personally speaking, I wasn't impressed by the number of climate scientists who rushed to propose a wide range of disparate ad hoc explanations for a statistically-insignificant surface temperature trend. Grant Foster (Tamino at Open Mind) has stressed this since at least mid-2009, and he was far from the only one. If I was to speculate, I'd say years of being attacked caused many climate scientists to flinch instead of standing by basic physics and statistics.

    For example, see open-access paper Foster & Rahmstorf (2011), Global temperature evolution 1979–2010, Env. Res. Lett. (2011)

    While it's true that the fake skeptic movement is finally running out of steam and that scientists can't write papers thinking largely about how their work might be misrepresented by liars, a little more awareness that their work would be deliberately misrepresented would have been advisable in some cases. After 30 years of attacks there's no justification for naivete.

    1. To clarify the above, Foster was one of those stressing the lack of statistical weight of the decadal trends, not trying to explain them.

      As Gavin Schmidt and Michael Mann are currently noting, these are not actually contradictory positions -- it's just a question of different time frames. But it's not hard to guess which one AGW deniers will jump on like starving dogs on a juicy bone.

    2. It is fine to look for explanations why in certain years the temperature deviates from the long-term trends. That is also interesting when the trend does not change and in fact is a large part of climatology. But a part of climatology that until recently did not give you the opportunity to publish in Nature.

    3. :)

      I suspect to some extent it's an example of scientific pedantry, which will float above the average person's head.

    4. @Magma

      totally agree, understandable to some degree (imo), but the narrative was handed over to the deniers to some extent

    5. Scientific pedantry got us to the moon. Accuracy is important for scientific progress.

    6. Victor, yes it's important to be accurate. I was thinking more in the context of Arthur Smith's comment below and the sub-texts in the paper, meant for those who understand the different "camps" in the context of "hiatus" discussions, rather than the science itself.

      In regard to the actual science in this paper, I don't see a lot of disagreement. It's solid research and good research questions.

      It's the postures in regard to communication and framing for the general public where there are differences. And deniers take glee in exploiting those differences.

  4. Good point Magma.

    It is very important statistical uncertainties are not discussed in any detail publicly, lest the overwhelmingly important message of ever escalating anthropogenic warming is lost to the general public.

    1. Of course they can and should be discussed, but clearly and carefully, knowing full well that unethical liars will exploit any ambiguity, whether in context or out.

      Speaking of which, I've been at this long enough to recognize the distinctive footprint of a trоll, 'Anonymous'.

    2. On the otherhand, consider the words of George Carlin:"Think of how stupid the average person is, and realize half of them are stupider than that.'

      Then consider Donald Trump's supporters ..... and if that isn't bad enough, consider further ....

      Magma, you say 'troll' - I just say a below average Trump supporter.

    3. Nah.
      Trump = Abomination

      And, should he get in, probably will trigger some sort of disaster.

  5. When I discuss this in a presentation, I try to point out that technically the hiatus was always real if one was willing to apply the term to a short enough period. E.g., all data show no warming from 1998 to 1999, 2000, 2001, etc. But then we are just talking about wiggles in the graph.

    But the thing I find most amusing is when deniers use the term hiatus (as WUWT did in the title of their article) as it clearly indicates that they know full good and well that the world is going to continue to warm.

  6. I wonder if all the authors read the final draft? I suspect that most had not.
    So who is the genius who inserted the unnecessary ambiguity?

  7. Co-author Ed Hawkins has blogged about the new paper: "the most recent observed 15-year trends are all positive, but lower than most previous similar trends in the past few decades. This is a clear demonstration that the rate of change has slowed since its peak." and notes that warming didn't match our expectations as represented by CMIP5 "the recent observations are all continuously outside the ±1σ spread of the simulations for a lengthy period, which is obviously unusual. It is also not just global temperatures that have been unusual – the tropical Pacific sea surface temperatures & winds have also behaved well outside the simulated range." -

    1. Thanks, Layzej. I notice that Ed Hawkins says that although he is co-author, he doesn't agree with every section in the paper. I don't think he's elaborated on why (though he does say what section).

      He also wrote a comment which essentially reflects what I wrote in the article:

      Thanks Gavin for the thoughtful comments. I agree the language used in this area has been far from ideal and many people have used the same words to mean different things.

      For example, I would agree that it is likely (though not certain) that there has not been a slowdown in the underlying rate of global warming (as defined by ocean heat content for example), but there has very clearly been a slowdown in the actual observed rate at the surface. It is the latter, and especially the relatively large difference between the mean of the simulations and observations, which is unusual and therefore requires an explanation. Explaining the wiggles is just as important as the overall underlying trend.


    2. The difference between scientists is probably the extent to which they view the importance of the PDO/IPO being in a cool phase and the extent they think it's particularly unusual. (I expect it will happen again in the future, too. That it's not anything particularly unusual in a scientific sense, just a coincidence. But I could be wrong. I'm not a climate scientist. I still think there's an element of "seeps and scams" operating, and people wanting to over-justify all the scientific discussion of what has become a denier talking point.)

    3. Do you know the sentence at the start of the ‘Claims and counterclaims’ section of the paper that Ed objects to? I'm rather to cheap to buy access :(

    4. Tamino says "no slowdown":

      I wonder if they aren't mostly talking past each other. Ed says "Probably the underlying rate hasn’t changed", so it seems he agrees with Tamino. That can't be what he's talking about when he says "there has very clearly been a change in the rate of global surface warming."

      He seems to mostly be looking at the wiggles around the trend and divergence between the simulations and observations.

      But I haven't read the paper so I may be way off.

    5. Yes, Ed seems to be relying on observations vs. CMIP5 results as his definition of unexpected. Even this I don't find convincing. If observations exceed *all* individual runs that would be unexpected, but that they occasionally fall outside the 2 sigma band is actually expected, otherwise it would be 100% confidence level, not 95%.

      And of course we know that actual forcings did not exactly match model forcings and observational datasets have some flaws, so it seems like they are really just upset at the *wording* - i.e., there's no scientific disagreement, just a semantic argument over what is and isn't a 'pause,' 'slowdown,' 'hiatus,' 'unexpected,' etc.

      It's also disappointing that they didn't address the published research by Cahill et al. and by Foster & Abraham that showed no 'pause.'

    6. Layzej, the sentence at the beginning of the poorly headed "claims and counterclaims" section, together with the rest of the para was:

      Recent claims by Lewandowsky et al. that scientists “turned a routine fluctuation into a problem for science” and that “there is no evidence that identifies the recent period as unique or particularly unusual”26 were made in the context of an examination of whether warming has ceased, stopped or paused. We do not believe that warming has ceased, but we consider the slowdown to be a recent and visible example of a basic science question that has been studied for at least twenty years: what are the signatures of (and the interactions between) internal decadal variability and the responses to external forcings, such as increasing GHGs or aerosols from volcanic eruptions?

      I don't know what Ed meant by saying he doesn't agree with that sentence. Eg does he think that paper said something different? (It's the fifth paper in the list of references I've included above.)

      The more I read Fyfe16 the less I'm enthused about it. If it's trying to be a review article it fails, because it leaves out key works. Eg no mention of the latest Mann et al paper, showing that if you plug actual forcings into the models they are very close to observed surface temperature. No mention of the papers from last year showing there's been no change in the longer term trend since the last time the trend changed (1970s).

      If it's meant to show something new, it doesn't. Or nothing startlingly new I can see. There was a bit of research in it, but what extra research they've done confirms work that other people have already published some time ago. It doesn't seem to me to add any radically new insights.

      Despite some of what's stated or hinted at by Fyfe16, it doesn't contradict other works. Eg it doesn't contradict Karl15 or any of the papers Lewandowsky was co-author in. It makes some thinly veiled criticism of Karl15, without being specific. At least that's how I read it. But it fails there too. Some scientists, with some justification, didn't much like Karl15 comparing trends back to the 1950s, because that period covers two distinct and different trends. However most deniers aren't picking up on that aspect, they are using Fyfe16 to claim that the NOAA dataset is wrong, which is silly and wrong of them. In any case, comparing trends back to the 1950s makes more sense to me than comparing trends for the very short sub-period from 2000 to 2014, which is one short period chosen by Fyfe16.

      Judith Curry is using it to sling off at some of the Lewandowsky papers, but they are all consistent with Fyfe16 (as stated in Fyfe16).

      Like I said earlier, if the paper wasn't taking snide potshots at other work, when it's not really justified, it would have been a much better paper. Not startlingly new, and a bit out of date before it was published. As it is, it comes across a bit like a paper that missed the boat (or missed the slowdown or any so-called "pause"). Last year was the hottest year on record. Even with the IPCC models (without using actual forcings), the surface temperature is well within the range of the CMIP5 multi-model mean.

    7. Sou has earned a reply from the authors here, particularly from Ed.

    8. PG I think Ed Hawkins specialises in this subject (he blogs about observation and models a lot), so I wouldn't pit my notions against his. Nonetheless, the bit that layzej quoted from Hawkins about "the tropical Pacific sea surface temperatures & winds have also behaved well outside the simulated range" seems out of place to some extent, because there's this passage in the paper, talking partly about prior research and (I think) partly about their own analysis:

      One of the many valuable ancillary benefits of this scientific activity has been an improved understanding of the role of ocean decadal variability in modulating human-caused global surface warming. For example, new research has shown that decadal timescale cooling of tropical Pacific sea surface temperature (SST) — which is linked to trade-wind intensification associated with the negative phase of the Interdecadal Pacific Oscillation (IPO) — made a substantial contribution to the warming slowdown11–14 (Fig. 2e). Since averaging over a large number of climate model simulations reduces the random noise of internal variability, and assuming a large contribution from internal variability in the slowdown, the mean of the multi-model ensemble (MME) could not be expected to reproduce the slowdown.

      A different perspective on the role of internal variability is obtained through the analysis of the individual models and realizations comprising the MME. In 10 out of 262 ensemble members, the simulations and observations had the same negative phase of the IPO during the slowdown period — that is, there was a fortuitous ‘lining up’ of internal decadal variability in the observed climate system and the 10 simulations15,16. These 10 ensemble members captured the muted early-twenty-first-century warming, thus illustrating the role of internal variability in the slowdown.

      Perhaps Hawkins meant outside the mean simulated range? Although I'm not sure that works well either.

  8. I think Matt England's anomalous trade winds were unusual.

    1. After around 2005, they appear to be unusual... to me anyway.

    2. Here's the paper.

      I wrote about that and another paper of Matthew England's last year, about how in the long run a blip of the type earlier this century has little significance. (It included the same IPO chart.)

    3. Well, I think that depends a bit on whether or not intensified winds come right back. The anomalous winds are thought to have been caused by a very warm Atlantic surface off the coastline of South America. Right now it does look to me like that situation is reforming.

  9. I love the way dbstealey has now decided that he can make something true by writing 'fact:' before it. Fact: I run faster than Usain Bolt. Nope, doesn't work for me.

    1. But its fun to see that for today's debate dbstealey has decided that the planet has stopped warming. On other days dbstealey says it is warming but that the warming is not due to CO2.

  10. "In all three observational datasets the most recent 15-year trend (ending in 2014) is lower than both the latest 30-year and 50-year trends."

    Is there any point in comparing trends over different lengths of time? A 15 year trend is going to vary a lot more than a 30 year trend, so it should be expected that sometimes the 15 year trend is lower than the 30 year trend, just as at other times it's higher.

  11. Ed Hawkins hints at one of the things I've been saying for a long time, which is the cause of the pause clearly happened after 2005. To me the evidence is pretty stout. The 30-year warming trend to 2006 is the highest 30-year trend: higher than to 1999. Despite 2010 being the warmest year, the 30-year trend to 2011 took dip, and it continued taking a dip... hanging our for awhile in the .16℃ range. And now it is gradually recovering. So to me the pause is there, it's tiny, and it's barely breathing. I won't really consider it completely dead until the 30-year trend reaches .18 ℃ per decade.

    1. Tamino has a good graph illustrating the changes to 30 year trends. To me the differences in trend over the last 25 years seem trivial, especially compared to the big switches that occurred earlier in the century.

    2. Sorry, I misattributed the graph above. It's taken from Fyfe16.

  12. So I think the difference between the "Tamino" take and the take in this Nature paper is a philosophy on what is explainable about Earth's climate. In principle it's an understandable physical system, so every little dip and blip has some physical cause, and scientists can try to track down what exactly was the process that led to each little fluctuation. On the other hand, from the Tamino perspective, all the little stuff is just (natural) "noise" - yes it has a cause, but it may be really hard to trace, and in the long run it averages to zero and doesn't matter. So thinking of natural variation as "noise", there was no slowdown. Thinking of it as explainable stuff, yes, there was a change that had some cause and there were a number that could explain it. I don't think either side is wrong, they just have different perspectives.

    1. I think that's a fair summary.

    2. And that is the gap that the deniers often exploit

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  14. Quoting Ed Hawkins,

    For example, I would agree that it is likely (though not certain) that there has not been a slowdown in the underlying rate of global warming (as defined by ocean heat content for example), but there has very clearly been a slowdown in the actual observed rate at the surface.

    The bolded bit really should end all arguments about whether AGW has stalled, paused, hiatused, gone on sabbatical, etc. The place to look for change in accumulated/(lost) energy in a system is in its largest heat sink. Whether the wiggles in the other 5% of the system are statistically significant trend changes or not is, I think, the very weakest evidence from which to make a case for OR against AGW. Trying to go toe to toe with our friends across the aisle on the basis of surface or tropospheric trends alone is still in their wheelhouse, and they will wallop it every chance they get. OHC is a full broadside to their position because all throughout the Great Millennial Hiatus decades, it has not only NOT slowed down, but appears to have accelerated.

    Where the discussion of surface and/or bulk upper air temperature trends is not moot is in the actual scientific discussion of the finer nuances of how and why the wiggles do what they do in the interest of better understanding the whole system. And to the extent that not all wiggles or trend deflections come solely from internal variability, how things like aerosol and other external forcing variability affects the system.

    I apologize if my comments seem redundant and/or overly strident, but I feel strongly enough about what I've written above to repeat them ad naseum. The statistical arguments of non-significant trend changes appear to my lay eyes to be sound methods, but my lay eyes also see perceptible trend differences in the surface and upper air trends that want explanation. In point of fact, I can satisfactorily explain them to myself by way of internal variability and down-trending TSI. IOW, the pure trend stats arguments are utterly unconvincing to me especially because they offer no physical explanation for what's happening.

    As a stalwart believer in the radiative theory of AGW, I can only imagine how that looks to someone undecided and less-informed.

    1. I agree with Brandon. When I explain AGW, after I use the blanket analogy I show the Skeptical Science graph of total heat/energy content rising in which surface, air, ice are tiny wedges. Then I show the graph of ocean temp/heat rising steadily with surface temp/heat line wiggling around it.

  15. I'll say the same thing I said at Tamino's: disambiguation of "hiatus" is needed. In a guest commentary on RealClimate threed months ago, Lewandowsky et al. distinguished four questions:

    1. Is there a “pause” or “hiatus” in warming?
    2. Has warming slowed compared to the long-term warming trend?
    3. Has warming lagged behind model-derived expectations?
    4. What physical mechanisms underlie the “hiatus”?

    The first two questions call for statistical approaches, and are apparently still under debate. The second two are about our understanding of climate physics as formulated by models, e.g. CMIP5. The 2014 Nature Geoscience commentary by Schmidt et al., Reconciling warming trends, answered "yes" to question 3, and addressed question 4 in some detail, attributing the discrepancy to “conspiring factors of [modeling] errors in volcanic and solar inputs, representations of aerosols, and El Niño evolution”.

    So, while the alleged “hiatus” may or may not exist statistically, interest in it has led to resolving some “noise” into forcings, and to refinements in coupled GCMs. That surely has value, not least by demonstrating that climate science is self-correcting and progressive, like any legitimate science. Whether or not that matters in the public arena, it does to me 8^)!


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