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Hiatus or Bye-atus?

Guest commentary by Stephan Lewandowsky, James Risbey and Naomi Oreskes

The idea that global warming has “stopped” has long been a contrarian talking point. This framing has found entry into the scientific literature and there are now numerous articles that address a presumed recent “pause” or “hiatus” in global warming. Moreover, the “hiatus” also featured as an accepted fact in the latest IPCC report (AR5). Notwithstanding its widespread use in public and apparent acceptance in the scientific community, there are reasons to be skeptical of the existence of a “hiatus” or “pause” in global warming [Ed: see also this previous post]. We have examined this issue in a series of three recent papers, which have converged on the conclusion that there is not now, and there never has been, a hiatus or pause in global warming.

We are not alone in coming to this conclusion; evidence for this has also been reported by Cahill and colleagues in a recent statistical change point analysis, which failed to identify a slowing in warming at any point in time during the last four decades.

But because this conclusion is potentially controversial, it requires a careful analysis of the conceptual landscape of research on temperature variation over the recent period.
To date, research on the “pause” has addressed at least 4 distinct 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”?

Those questions are not only conceptually distinct, they also involve different aspects of the data and entail different statistical hypotheses. Nonetheless, those questions have frequently been conflated in the literature, and by using a single blanket term such as “pause” or “hiatus” for distinctly different phenomena and research questions, unnecessary confusion has resulted.

To reduce this confusion, our recent work has been exclusively concerned with the first question: Is there, or has there recently been, a “pause” or “hiatus” in warming? It is this question—and only this question—that we answer with “no”, based on multiple lines of evidence:

In an article published in BAMS this year (Lewandowsky et al, 2015), we reported on the results of a blind expert test by professional economists. Blind tests are the methodological gold standard in many fields of enquiry, from pharmaceutical research to cognitive science. The economists in our sample were shown the global temperature data (NASA’s GISTEMP) but it was labeled as “world agricultural output” as shown in the figure below.



The experts had to evaluate a statement accompanying the graph which read: “A prominent Australian critic of conventional economics, Mr. X., publicly stated in 2006, that ‘There IS a problem with the growth in world agricultural output—it stopped in 1998.’ A few months ago, Mr. X. reiterated that ‘…. there’s no trend, 2010 is not significantly more productive in any way than 1998.’ ” This statement was an exact translation, into economic terms, of a series of public statements by an Australian contrarian (Bob Carter) claiming that global warming had stopped.

The experts in our sample clearly disagreed with the notion of a pause or hiatus: Experts rejected the idea that the data confirmed the statement and they instead found the data to contradict the accompanying statement. The experts also found the statement to be misleading and ill-informed. And nearly two thirds of our experts endorsed the possibility that the claim of a pause or hiatus might be fraudulent in light of the data.

In a second article, just published in Scientific Reports (Lewandowsky et al, 2015b), we followed up on this experimental test with a formal statistical analysis that buttressed the conclusions of the blind expert test. We began by considering a corpus of 40 peer-reviewed articles that have addressed the pause and inferred from those publications what those authors considered to be the onset year of the pause. Did the pause commence in 1998? 2001? Or some other year? We found that there was considerable variation, shown by the blue histogram in the figure below, which shows the distribution of presumed onset times together with global temperatures during the modern record of global warming.



The histogram shows that the presumed onset of the pause spanned an entire decade (1993-2003). The mean presumed duration of the pause across the 40 articles was 13.5 years. We next took the onset and duration of the pause reported by each article and compared the associated decadal temperature trends against the distribution of all possible trends of equal duration during the last few decades. If there were a pause, we would expect the distribution of trends in the literature to differ considerably from the distribution of all trends of equivalent duration.

Because there is some disagreement about the onset of modern global warming, we used three reference dates for our comparison involving all possible trends: the year 1951, used by the IPCC in AR5, and 1964 and 1976, which are 2 standard deviations below and above and below the mean estimate of the year of onset of modern global warming derived by the Cahill et al change-point analysis.

The results are shown in the 3 histograms below, with onset times 1951, 1964, and 1976 from left to right. The vertical red lines in each panel represent the long-term trend (1951–2012) used by the IPCC in the AR5. The solid line is for the GISS dataset analyzed here, and the dashed line is the long-term trend for the same period (.12K/decade) in the UK Met Office’s HadCRUT4 data set.



This analysis shows that the distribution of warming trends labeled as the pause by the literature is indistinguishable from the overall distribution of trends that have been observed from the middle of the 20th century onward. When 1964 or 1976 are instead used as onset of warming, then the distribution of trends labeled as a pause does sit at the lower end of the overall distribution, but it is still by no means consistently extreme or unusual.

Additionally, virtually all articles on the pause referred to a time period during which the decadal warming trend exceeded zero (the black vertical line). This is incompatible with standard dictionary definitions of a pause or hiatus, which cite a process that has been suspended or stopped. Periods in which warming continued (>0 K/decade), by definition, cannot be a pause or a hiatus.

For the notion of a hiatus in warming to be scientifically well-founded, there must either be a demonstrable and statistically-relevant absence of any trend in global temperatures or, minimally, the observed trend must differ in a statistically identifiable way from the historical record. With conventional frequentist statistics, the absence of a trend is difficult to establish, and results can be affected by vantage point. That is, different results may arise depending on when one chooses to look backward in time, not because anything notable has happened but because natural variability can override a long-term trend if only brief periods of time are considered and if the end points of the trend are varied.

We therefore compared the alleged pause against all possible historical trends once more, but this time across all possible historical vantage points during the last three decades. From each vantage point, we look backward in time a varying number of years and determine the magnitude and significance of the trend. The results are shown below using GISTEMP:



The top panel (A) shows the warming trends that were observable at any vantage point between 1984 and 2014 (horizontal axis). For each vantage point, between 3 and 25 years were included in the trend calculation (vertical axis). So for example, looking backward from 2014, no matter how many years were included in the trend, all trends were positive. When 15 years are included, then the trend becomes statistically significant (hence the dot in the cell at latitude 15 for the last column). By contrast, in 2000, the most recent 3 or 4 years exhibited cooling, but by the time 15 years were included the trend was again significant. The bottom panel of the figure (B) presents the same data using a ternary classification of p-values for the linear trend into non-informative (p>.10; beige), partially informative but not conventionally significant (.10 > p >.05; gray), and significant (p < .05; terracotta). This panel also includes three diagonal lines that identify the earliest calendar year included in the analysis. Any observation to the below and to the right of the line labeled “1975” only includes observations later than that, and so on for the other two lines. The observations above and to the left of the 1965 line go back to 1960 (top-left corner; looking back 25 years from 1984 inclusive).

The figure shows that at every year during the past 30 years of modern global warming, the immediately preceding warming trend was always significant when 17 years (or more) were included in the calculation. In a number of cases—including in 2014—fewer years were required to reach significance, but never more than 17. This result should not be surprising: Significance requires statistical power to be detected, and the more observations are considered the greater the power of the analysis. The fact that a trend fails to reach significance with, say, only 5 or 10 years of data is therefore non-informative: no matter how robust the warming trend, once natural variability is superimposed on the trend, it will escape statistical detection with a small sample. To conclude from that that global warming has “stopped” is unwarranted. Nevertheless, a number of papers in the peer-reviewed literature have done just that. That is, they concluded that there was a pause in warming using a time period that was too short to achieve conventional statistical significance.

To illustrate, we used the definitions of the pause found in our corpus of articles (mean duration 13.5 years), and asked how often the null hypothesis of no warming would fail to be rejected during the last 30 years. It turns out that during those 3 decades, the 14-year trend escaped significance 10 times and the 13-year trend 13 times, suggesting either that global surface warming “paused” between 30% and 43% of a time period during which the Earth warmed 0.6K overall, or that global surface warming never paused and what we have been observing are routine fluctuations superimposed on a warming trend.

Taken together, the statistical and behavioral evidence demonstrate that the notion of a pause or hiatus—as commonly understood—is incorrect. The evidence from the blind expert test suggests that it is also misleading.

The question of a recent pause in warming is distinct from the matter of fluctuations in warming rates over any particular time period of interest. It is uncontroversial that the climate system is highly variable and, as our analysis shows, there have been many fluctuations, both positive and negative, as compared to the longer term warming trend. It is a valuable research endeavor to examine why these fluctuations occur, and to what extent models and observations may on occasion diverge. Such research has the potential to improve our overall understanding of the climate system.

This brings us to our final issue: If there is no pause and there was no pause, why did the recent period attract so much research attention? We can suggest a number of reasons. One is a matter of semantics. Many articles on the pause addressed not the absence of warming but were concerned with a presumed discrepancy between models and observations. We do not believe that those articles should have been framed in the language of a “pause,” but that does not mean their method or findings are compromised.

A second reason is that owing to the incessant challenge of climate science by highly-vocal contrarians and well-organized ‘Merchants of Doubt’, scientists may have become not only reticent in reporting the full spectrum of risk they are concerned about for the future (see for example Brysse et al, 2013), but have also subtly changed the way in which they approach their science. We explored the possible underlying mechanisms for this in an article earlier this year (Lewandowsky et al, 2015c). In a nutshell, we argue that scientists have unwittingly been influenced by a linguistic frame that demonstrably originated outside the scientific community, and that by accepting the word “pause,” scientists have subtly framed their research in ways that our statistical and behavioral analysis has revealed to be inappropriate.

When scientists use the terms “pause” or “hiatus” they may indeed know—and their colleagues may understand—that they do not mean to imply that global warming has stopped. The problem is that words such as “pause” or “hiatus” have vernacular meanings, and when scientists use a term from the public vernacular to describe a feature of science, confusion results when the vernacular term is an inappropriate description of that feature. Scientists might tacitly understand that global warming continues notwithstanding the “pause,” or they may intend “pause” to refer to differences between observed temperatures and model-derived expectations, but the public is not privy to that tacit understanding.

References

  1. N. Cahill, S. Rahmstorf, and A.C. Parnell, "Change points of global temperature", Environmental Research Letters, vol. 10, pp. 084002, 2015. http://dx.doi.org/10.1088/1748-9326/10/8/084002
  2. S. Lewandowsky, J.S. Risbey, and N. Oreskes, "The “Pause” in Global Warming: Turning a Routine Fluctuation into a Problem for Science", Bulletin of the American Meteorological Society, vol. 97, pp. 723-733, 2016. http://dx.doi.org/10.1175/BAMS-D-14-00106.1
  3. S. Lewandowsky, J.S. Risbey, and N. Oreskes, "On the definition and identifiability of the alleged “hiatus” in global warming", Scientific Reports, vol. 5, pp. 16784, 2015. http://dx.doi.org/10.1038/srep16784
  4. K. Brysse, N. Oreskes, J. O’Reilly, and M. Oppenheimer, "Climate change prediction: Erring on the side of least drama?", Global Environmental Change, vol. 23, pp. 327-337, 2013. http://dx.doi.org/10.1016/j.gloenvcha.2012.10.008
  5. S. Lewandowsky, N. Oreskes, J.S. Risbey, B.R. Newell, and M. Smithson, "Seepage: Climate change denial and its effect on the scientific community", Global Environmental Change, vol. 33, pp. 1-13, 2015. http://dx.doi.org/10.1016/j.gloenvcha.2015.02.013

92 Responses to “Hiatus or Bye-atus?”

  1. 1
    Silk says:

    What about ‘slowdown’?

    It appears to me there is no real evidence that the /rate/ of warming has decreased.

    Any comment on that?

  2. 2
    Andy Revkin says:

    This line of inquiry is helpful, as is all of the ongoing inquiry into possible geophysical reasons for recent short-term variations in temperatures and trends, whatever label you ascribe to them. But I have two questions about the concerns related to semantics.

    1) I was casting about for other examples of this semantic challenge. One seems to be “cancer clusters.” This label is often applied to implicitly unprovable situations (where a community is too small, and a cancer too rare, ever to know if there’s a relationship to a particular cause). This web search shows both sides of this: http://j.mp/cancerclusternews It seems impossible to describe the negative finding without referring to the term.

    2) I see ripe possibilities for doing a similar analysis of other characterizations of the climate change problem. One is that the science is now “worse than we thought.” When I look back at descriptions of sea level change, the possible temperature rise, and other impacts in, say, the 1980s ( http://j.mp/rev1988 ), I don’t see evidence this is the case. Hurricane findings are not “worse than we thought.” Sea level rise projections (through 2100 or so) remain highly uncertain because of fundamental uncertainties in ice sheet dynamics, while long-range change is undeniable (centuries of rising seas).. etc.

    Thoughts welcome.

  3. 3
    Jim Baird says:

    A statistical demonstration that there has been no “pause” or “hiatus” is not the same as saying that between 1998 and 2013 the bulk of the heat didn’t go someplace other than the atmosphere.

    IMHO, there are significant lessons to be learned from what actually took place.

  4. 4
    Tom O'Reilly says:

    What F***ing Hiatus?

    Global warming and El Nino make 2015 hottest year ever on record: BOM
    http://www.abc.net.au/worldtoday/content/2015/s4360264.htm

    Global warming and El Nino set to make 2015 the hottest year on record, WMO says
    http://www.abc.net.au/news/2015-11-25/2015-set-to-be-hottest-on-record-wmo-says/6974530

    The Australian national October mean temperature was 2.89 °C above the long-term mean and the highest on record for any month of the year (surpassing the record of +2.75 °C set in September 2013). Maximum and minimum temperatures were also the warmest on record nationally for October, with respective anomalies of +3.44 °C for maxima (also warmest on record for any month, surpassing the record of +3.41 °C set in September 2013) and +2.34 °C (placing fourth-warmest on record for any month).

    All States and the Northern Territory placed in the top ten maximum temperature records for October; New South Wales, Victoria, South Australia, and Western Australia observed their warmest October on record. All regions except Tasmania and the Northern Territory placed in the top ten minimum temperature records for October.
    http://www.bom.gov.au/climate/current/month/aus/summary.shtml

  5. 5
    Russell says:

    The issue is less semantics than semiotics: science is not ordinarily concerned with the creation and manipulation of symbols, but that is what ‘framing ‘ is all about– the climate wars are anything but disinterested, and it is hard to deny the continuity not just of public personalities, but of rhetoric and supporting institutions, many investing in both media and public relations expertise.

    Could a double-blind study be designed to provide a less tacit understanding of whether any hiatus or sociological discontinuity in fact exists between the collective antiwar, antinuclear, and alternative energy activism of earlier decades, and that of today ?

    It is , after all, the authors who:

    argue that scientists have unwittingly been influenced by a linguistic frame that demonstrably originated outside the scientific community, and… have subtly framed their research in ways that our statistical and behavioral analysis has revealed to be inappropriate.

  6. 6

    @1 (Silk): Yes, I think slowdown or fluctuation are good terms. We settled on fluctuation in the BAMS paper.

    @2 (Andy Revkin): Concerning your second point, I am not aware of a recent systematic examination of the issue. Freudenburg and Muselli showed in 2010 (GEC, 20, 483-491) that new findings were more than 20 times as likely to reveal projections to have been too conservative than too “alarmist.” There is also much evidence to suggest that scientists generally are (too?) reticent; e.g. Brysse et al (2012); Hansen (2007); Risbey (2008). We argue that this natural reticence is amplified by the contested nature of climate science (Lewandowsky et al., 2015, GEC). But at the moment I cannot think of a more recent update of the Freudenburg and Muselli-style analysis.
    @3 (Jim Baird): Agree entirely. Much to be learned, and we contributed to the discussion (Risbey, Lewandowsky, Langlais, Monselesan, O’Kane, & Oreskes, Nature CC, 2014).

    @5 (Russell): Interesting point about semiotics generally. The specific question about sociological discontinuity escapes me, however. Can you clarify? How would continuity be manifest? And in what way could it be discontinuous?

  7. 7
    Titus says:

    As a member of the public I observe that the earth has been warming since the end of the little ice age of the mid 19th century. Temperatures in the last 20 odd years have been pretty flat or ‘paused’ as this article describes. No problem with that.

    So, is it going to carry on rising or start a decline? Historical scientific predictions said ‘rising’. Observations show ‘pause’. So public are sceptical.

    What scientific ‘tacit’ understanding am I missing?

  8. 8
    Jim Eaton says:

    I’m know this falls under the weather, not climate category, but we now have another unprecedented 2015 event happening right now. Major hurricane Sandra (a category 4 storm which fortunately just dropped to a 2) is headed towards Mexico just south of the Baja California peninsula. This is the first major hurricane ever to exist this late in the year in the Western Hemisphere (eastern Pacific or Alantic oceans). As Dr. Jeff Masters of the Weather Underground puts it:

    “Remarkable Hurricane Sandra exploded into a Category 4 storm with 145 mph winds overnight, making it the latest major hurricane ever observed in the Western Hemisphere (November 26.) The previous record was held by an unnamed Atlantic hurricane in 1934 that held on to Category 3 status until 00 UTC November 24. Sandra is also now the latest Category 4 storm ever observed in either the Eastern Pacific (previous record: Hurricane Kenneth on November 22, 2011) or the Atlantic (previous record: “Wrong Way” Lenny on November 18, 1999.) Prior to Sandra, the strongest East Pacific hurricane so late in the year was 1983’s Winnie, which topped out on December 6 at 90 mph winds. Sandra is the first major hurricane in the Western Hemisphere that has ever been observed on Thanksgiving Day. According to WU contributor Phil Klotzbach (Colorado State University), Sandra is on track to become the latest landfalling tropical cyclone on record for Mexico, beating out Tara (Nov. 12, 1961). An Air Force Hurricane Hunter mission is scheduled for Sandra on Friday afternoon.”

    It looks like Texas (again) and the southern plains are in for some extremely wet weather. We can argue about how slow or fast sea level is rising, but Mother Nature is showing us a lot of new changes that were generally predicted to occur decades into the future. Hold on to your hats folks, it looks like the roller coaster already is speeding down the tracks.

  9. 9
    Patrick says:

    Oh dear. It’s sad when such convoluted arguments have to be invoked to justify past arguments when real science shows otherwise. Remember Hoyle and the star formation saga?
    Since the IPCC first made its predictions in 1990, all five of the longest-standing global temperature datasets – three terrestrial and two satellite – have shown warming rates well below even the lower bound of the IPCC’s very wide interval of predicted global warming.
    Remarkably, the IPCC’s predicted rate of warming is three times the UAH observed trend of just 0.24 C° since 1990.
    And now we read that CO2 residence time said to be 40 years, not 1000 per previous claims

  10. 10
    Silk says:

    #6 Nobody could look at the temperature record and claim there was a pause. Or at least, nobody who wasn’t in serious denial.

    If those were crime stats and I were to claim to an audience that the data showed crime wasn’t increasing, I’d be jeered out of the room.

    The only people who can look at that time series and see a ‘pause’ are people who would do anything to avoid having to reduce emissions.

    Statistically that time series shows no pause (did you bother to read the article?). Socialogically it also shows no pause UNLESS YOU WANT TO SEE ONE.

  11. 11

    #6,Titus–

    You may want to work on your reading for comprehension skills; the statement that:

    Temperatures in the last 20 odd years have been pretty flat or ‘paused’ as this article describes.

    …is pretty much exactly wrong.

    As to your question:

    …is it going to carry on rising or start a decline?

    …you may wish to read Tom O’Reilly’s comment at #4.

  12. 12
    chris says:

    Titus, the ‘tacit’ scientific understanding you’re missing is really just (non-tacit) scientific understanding!

    Our understanding of the world, and thus the ability to make predictions is based on an understanding of the causal relationships and their magnitudes. It’s not based on “just looking at stuff” or fitting curves and extrapolating or whatever. It’s beyond question that the earth’s surface temperature responds to an increased radiative forcing with warming. Since we know that the greenhouse contribution to enhanced forcing is increasing (no-brainer – we’re emitting humoungous amounts of greenhouse gas) and can observe that the solar contribution to forcing has been steady (marginally reduced in fact) since the 1950’s, and have a good handle on volcanic contributions and so on….

    …our understanding tells us that the earth will continue to warm as the surface temperature comes towards equilibrium with enhanced forcing acrued (and enhanced forcing still to come).

    Temperature in the last 20 years haven’t really been “pretty flat” have they? NASA Giss has 1994 temperature anomaly of 0.32 and a 2014 anomaly of 0.74. That’s 0.4 oC rise in surface temperature in 20 years. 2015 is pretty certain to break the record….

  13. 13

    @1 (Silk): Yes, I think slowdown or fluctuation are good terms. We settled on fluctuation in the BAMS paper.

    @2 (Andy Revkin): Concerning your second point, I am not aware of a recent systematic examination of the issue. Freudenburg and Muselli showed in 2010 (GEC, 20, 483-491) that new findings were more than 20 times as likely to reveal projections to have been too conservative than too “alarmist.” There is also much evidence to suggest that scientists generally are (too?) reticent; e.g. Brysse et al (2012); Hansen (2007); Risbey (2008). We argue that this natural reticence is amplified by the contested nature of climate science (Lewandowsky et al., 2015, GEC). But at the moment I cannot think of a more recent update of the Freudenburg and Muselli-style analysis.
    @3 (Jim Baird): Agree entirely. Much to be learned, and we contributed to the discussion (Risbey, Lewandowsky, Langlais, Monselesan, O’Kane, & Oreskes, Nature CC, 2014).

    @5 (Russell): Interesting point about semiotics generally. The specific question about sociological discontinuity escapes me, however. Can you clarify? How would continuity be manifest? And in what way could it be discontinuous?

  14. 14
    Mal Adapted says:

    Titus:

    Temperatures in the last 20 odd years have been pretty flat or ‘paused’ as this article describes. No problem with that.

    You’ve misread the article, as it describes the opposite of your understanding. From the first paragraph:

    We have examined this issue in a series of three recent papers, which have converged on the conclusion that there is not now, and there never has been, a hiatus or pause in global warming.

    You go on to say:

    So, is it going to carry on rising or start a decline? Historical scientific predictions said ‘rising’. Observations show ‘pause’. So public are sceptical.

    What scientific ‘tacit’ understanding am I missing?

    Whatever tacit assumptions you are making, you are missing the explicit understanding that temperatures have continued rising largely as projected, the more so when observations from the last two years are included. The observed slowing between 1998 and 2013 raised the 4th question asked in the OP, with some answers emerging already: for example, last year Dr. Schmidt and two colleagues published an article (paywalled, but I’ll bet he’d send you a PDF if you asked him nicely) discussing how the CMIP family of models can better resolve short-term “noise” to forcing by greenhouse gasses, solar irradiance, ocean circulation, and anthropogenic and volcanogenic aerosols. The public can thus be satisfied that climate science is progressing as it should.

  15. 15
    Adam R. says:

    Titus, your observations have been incomplete, it seems. Even to the naive layman’s eye, surface temperatures do not appear flat if one looks at data through 2015.

    Observations show no pause. They never did in the long term trend and now don’t even in the naked, year-to-year data. That is what you are missing.

  16. 16
    Jim Eager says:

    Titus wrote: “Observations show ‘pause’.

    Only if you keep your eye on the dog.
    But if you want to know about the trend in climate you need to keep your eye on the man.

    Neil deGrasse Tyson explains:
    https://www.youtube.com/watch?v=cBdxDFpDp_k

    How long does it take to discern the underlying trend in climate from the “noise” of weather and year to year natural variation?

    Longer than the so-called ‘pause’.

    Robert Grumbine explains:
    http://moregrumbinescience.blogspot.ca/2009/01/results-on-deciding-trends.html

    The pause never was.

  17. 17
    Treesong says:

    Titus: You’ve missed the tacit understanding that there hasn’t been a pause, only a slowdown. Try reading the article.

  18. 18
    Chuck Wilson says:

    Titus @6.
    You are missing an understanding of the 1st Law of thermodynamics and the role that forcings play in climate. The 1st Law for a closed system (no mass exchange with surroundings but heat exchange) says that the increase in internal energy must equal the net heat that entered the system minus the work done by the system. The net heat is the absorbed energy from the sun minus the thermal radiation escaping to space. The work is negligible (try telling that to someone whose house was ripped apart by Sandra – but it is true.) The system is the atmosphere + the oceans + the land (down to a few hundred meters) + the cryosphere. NOAA MSUs (see UAH), ARGO (and predecessors), boreholes and GRACE track the thermal state of these elements of the climate system. Internal energy of the climate system has increased by about 275 ZJ since 1971 (Box 3.1 of IPCC AR5 WG1). So where did this energy come from?
    Murphy et al., 2009 show us that added greenhouse gases have added several times this amount of energy over that time period. Humans added those gases. Those gases added energy to the climate system by reducing the amount of thermal radiation escaping to space (the greenhouse effect) and the internal energy went up. It is a causal chain. A climate with higher internal energy is expected to have warmer temperatures, less ice and more water vapor. All that has happened.
    The correlation between global average surface temperature (GAST) and CO2 abundance is not perfect because the elements of the climate system exchange energy with each other in chaotic ways (What ’causes’ ENSO, the PDO, the AMO?). But energy is governed by the 1st Law, and the measurements show that the internal energy of the climate has gone up. Quantum mechanics (GHG absorption in IR) tells us why.
    We do not expect any major downturn in GAST because we are still increasing the abundance of GHGs and they will continue to increase the internal energy of the system with attendant increases in temperatures, melting and water vapor content of the atmosphere.
    Chuck Wilson
    Golden Colorado

  19. 19
    Chuck Wilson says:

    Thanksgiving.
    I am thankful for this article and grateful to its authors for clarifying much over the years. Too late for my last class but in time and bookmarked for the next one.
    I am thankful for the return of RealClimate.org to normal web-life.

  20. 20
  21. 21
    John Drayton says:

    Titus asks “What scientific ‘tacit’ understanding am I missing?”

    Titu, what you seem to be missing is a connection to actual observations. You claim to “observe that the earth has been warming since the end of the little ice age of the mid 19th century”, but supply no evidence. In fact on the page you comment on are graphics indicating a mild decline from mid/late 19th century through to early 20th century.

    You also claim that “temperatures in the last 20 odd years have been pretty flat or ‘paused’ as this article describes”, yet the authors of the article explicitly state “We have examined this issue in a series of three recent papers, which have converged on the conclusion that there is not now, and there never has been, a hiatus or pause in global warming”.

    Finally, you say ask “So, is it going to carry on rising or start a decline?”, concluding that “observations show ‘pause’”, again with no evidence. I have no idea how you can hold on the the idea that observations show a pause, especially in light of the fact that 2014 was a record high, and that 2015 is pretty much guaranteed to exceed 2014 by a notable margin.

  22. 22
    R. Zaharia says:

    Respect and Relief…

    It seems to me that the 3 of you deserve to be commended !
    While reading this article, the words that came in my mind were “Fisrt class thinking… Fisrt class analysis… Excellent science” !

    All the more of this feeling, since I happened to come on this web page, just after reading… the Lamar Smith “Bullying letter” of Nov. 4 to K. Sullivan, Head of NOAA, on the very same issue ! (But with a… “Stone age” approach !)
    Relief is a common feeling when going from a stinking place to a nice garden or an art museum ! (Indeed a well written & “to the point” article, may be seen as an artwork !)

    What a pity that the House Committee on Science, Space, & Technology doesn’t know the value of reprocessing !
    What a pity that these folks still ignore that one of the best “$ values” they are supposed to overlook for taxpayers, sits in periodical reprocessing of available time series of observations ! (& more particularly, before performing Met reanalyses.)

  23. 23

    Because I don’t want to post in the about-to-die November page, I’d like to beg the editors’ indulgence and post a very minor announcement here–I’ve added a new page to my web site giving the reasons we know the present warming to be artificial.

    http://bartonlevenson.com/AnthropogenicCO2.html

  24. 24
    Vincent says:

    First, from what I’ve observed (on Facebook and elsewhere), the global warming denialists have since a while moved onto claiming that the satellite data (specifically, the RSS analyses) don’t show any warming, and they just ignore the ground measurements despite being direct measurements.

    Second, on a more serious note, you say you’re calculating correlation coefficients on annual global temperature means. But how is such an analysis justified? A P value represents the odds that the actual data were found assuming that the null hypothesis is true in the population that the random sample was drawn from (so, if a P value is too small, we reject the notion that the null hypothesis is true in the population). But when talking about an interval of annual global means, these values aren’t drawn from a “greater population” of annual global means that we want our sample to generalize to–after all, we just want to say something about that specific interval! It doesn’t make sense, to me, to use annual global mean as a random factor.

    So why would a simple correlation calculated over annual global means be appropriate? I don’t understand that. Or I’m missing something. If someone could point out what I’m misunderstanding, I’d greatly appreciate that! Sorry if I’m being stupid.

  25. 25
    Titus says:

    Just to clarify, I did not come up with the word ‘pause’. That came from the article. I said temperatures were ‘pretty flat’. I may add here that they are very flat in consideration of what was strongly predict years ago.

    Patrick @8 explains it much better than I:
    “Oh dear. It’s sad when such convoluted arguments have to be invoked to justify past arguments when real science shows otherwise”

    Read his entire comment. I’d say he’s close to what the general ‘public’ think.

  26. 26
    Chris O'Neill says:

    “Titus”:

    I observe that the earth has been warming since the end of the little ice age of the mid 19th century.

    No you didn’t. There was no observed warming in the second half of the 19th century: http://www.woodfortrees.org/plot/hadcrut4gl/to:1900/trend/plot/hadcrut4gl

    What scientific ‘tacit’ understanding am I missing?

    If you miss facts such as the above then you’re certainly going to miss understanding.

  27. 27
    Don Cox says:

    How the graph looks depends very much on whether you plot a one, five, ten or twenty year running average.

    The longer the period, the less any “pause” will show.

    We also need to distinguish clearly between the temperature, the change in temperature, and the rate of change in temperature. This kind of thing can confuse the general public.

  28. 28
    Chuck Hughes says:

    Here’s a “little” caveat that the Scientific Community should take into serious consideration when discussing emerging Scientific Truths to the public…

    “The study of 160,000 people by the Organization for Economic Cooperation and Development, which is composed of two dozen developed nations, found that U.S. adults had reading levels that were below average, and lagged far behind those of Japan (which scored at the top), several Scandinavian countries, Australia and Korea. Test takers in Spain, Italy, Ireland and several other countries hardest hit by the Great Recession scored lower than Americans did.

    Americans also scored lower than average in math and technological problem solving.

    “It’s long been known that America’s school kids haven’t measured well compared with international peers,” the Associated Press wrote in a survey of the study. “Now, there’s a new twist: Adults don’t either.” And it appears students who leave high school without certain basic skills are not learning those skills later in adult education or job training programs.”

    http://www.latimes.com/books/jacketcopy/la-et-jc-american-adults-have-low-and-declining-reading-proficiency-20131008-story.html

    In regards to #6, I think that’s the problem we’re facing here. My guess is that there is a tremendous disconnect between policy makers and the Scientific Community at large. Why else would people believe vaccinations cause Autism? If you can’t get past that how in the world do you expect people to understand our dire situation in regards to Climate?

    You’ve got so many mitigating factors that are not being addressed that have absolutely nothing to do with Climate Science but, are a barrier between the public and the scientific community. These factors have not been and are not being addressed. Until they are I don’t see any progress being made in the near future. We’re effectively ‘Stuck’. Politicians in America are NOT elected due to their ‘intellectual’ prowess. They mirror the constituents who placed them in the position of making crucial decisions.

    This “Trumps” everything…. if you know what I mean.

  29. 29
    Jim Eager says:

    Patrick wrote: “And now we read that CO2 residence time said to be 40 years, not 1000 per previous claims

    It’s truly sad when such lame arguments are resorted to.

    Be careful what you read, and always read for comprehension. There is a very big difference between the residence time for an individual CO2 molecule vs the residence time for an increase in the CO2 species as a whole. The former is measured in decades, the latter in centuries to millennia.

  30. 30
    Chuck Hughes says:

    I think someone is messing with this site. Every-single-time I try to log in I get an error message or Server Down due to maintenance. This never used to happen before. And it’s not just me. I also have to copy all my posts before sending because half the time it doesn’t go through. I wish there were some tech people to investigate this.

  31. 31
    Paul P says:

    So what are the circles – do they represent claims by contrarians that there has been an hiatus during the relevant period?

  32. 32
    Henk Schuring says:

    @8 Patrick:
    The “predictions” always have an “if…, then” character. If climate forcings develop in this or that way, then we expect this or that result. I assume you aim at the 1988 Hansen predictions. Climate forcings (all greenhouse gases, not just CO2; aerosols; solar irradiance; and more) developed in such a way that the lowest scenario [C] was even a little bit to high. The temperature development matches the forcing development. This means that climate science still does a fine job calculating what will happen if we keep on increasing the climate forcings.
    see e.g. Tamino on this: https://tamino.wordpress.com/2014/03/21/hansens-1988-predictions/

    And why do you pick the lowest temperature record as a comparison. Satellite measurements have had their issues in the 90’s and they seem to have them now: From the Washinton Post: “Andrew Dessler, a climate researcher at Texas A&M University, says he is skeptical of the satellite data’s reliability. “As far as the data go, I don’t really trust the satellite data. While satellites clearly have some advantages over the surface thermometer record, such as better sampling, measuring temperature from a satellite is actually an incredibly difficult problem. That’s why, every few years, another big problem in the UAH temperature calculation is discovered. And, when these problems are fixed, the trend always goes up”
    You might also read this article:
    http://iopscience.iop.org/article/10.1088/1748-9326/7/4/044018;jsessionid=58E1CD5AE26EA87764A5403521E42910.c3.iopscience.cld.iop.org#erl441194s3

  33. 33
    Richard Caldwell says:

    Chuck Wilson: The system is the atmosphere + the oceans + the land (down to a few hundred meters) + the cryosphere.

    Richard Caldwell: Therefore, anybody who lists “6′ above the surface atmospheric temperatures” and then draws a conclusion about global warming is being truly silly at best. The BIG number this post should have mentioned is the total average temperature of the oceans, atmosphere, and perhaps 100 meters of land surface. As written, this post says very little about global warming or the “pause”. When variations are not due to measurement errors and not due to unknown stuff, then it is imperative to include all knowns before chucking everything else into the “noise” bin. Data with 50% error bars is better than just leaving it null. (Like that old sea-level choice, “We don’t know how much ice will melt, so we’ll just use zero in our equations!)

    ……….

    John Drayton: I have no idea how you can hold on the the idea that observations show a pause, especially in light of the fact that 2014 was a record high, and that 2015 is pretty much guaranteed to exceed 2014 by a notable margin.

    Richard Caldwell: Uh, pauses end. That 2014 and 2015 are much higher helps show that it was merely a pause. But what “paused”? If one just takes the 0.025% of the data represented by atmosphere temperature (actually even less as it’s just the 6′ temperature used), AND one accepts 1998 and 2009 as “solid anchor points”, then from 1998 to 2009 or so, temperatures did “pause”. That says almost nothing about “global” warming, but if one just looks only at that short time period of a narrow slice of the planet, the pause was real – It’s a “gotcha” definition of “pause”. (Semantically, even a single year (or month) where a new record high wasn’t set could be called a “pause”.) Personally, I don’t think it’s wise to bet the planet on “gotcha semantics”, but in any case, the “pause” ended either in 2010 or 2014.

    Instead of saying (what looks patently silly to laymen, that), “There was no pause in surface record temperature increase.” scientists should say, “When looking at a tiny subsection of the system, pauses and retractions are guaranteed. The system as a whole increased in temperature in absolute lockstep. Systemwide, there was not even the slightest slowdown, let alone a pause.”

    That whole “30 years to make climate” is absurd. It takes perhaps one year (one could say one minute), if one has all the data. In our case, the timeframe required is shrinking fast as we learn more and more about all the variables. I’d be interested to see a paper which uses only 1998-2013 data to estimate climate change.

  34. 34
  35. 35
    Hank Roberts says:

    Armando gives a link to one figure from the paper:

    Volcanic contribution to decadal changes in tropospheric temperature
    Nature Geoscience 7, 185–189(2014)
    doi:10.1038/ngeo2098

    Armando should read the text instead of eyeballing one figure and mistakenly thinking it supports his argument.

  36. 36

    #33–Richard Caldwell

    That whole “30 years to make climate” is absurd. It takes perhaps one year (one could say one minute), if one has all the data. In our case, the timeframe required is shrinking fast as we learn more and more about all the variables. I’d be interested to see a paper which uses only 1998-2013 data to estimate climate change.

    I think you are on your own island on that, RC…

  37. 37
    Armando says:

    What’s my argument Hank?

    B.T.W. what do you think of the paper?

  38. 38
    Steve Fish says:

    Regarding removing variability from the surface temperature record I remembered this RC post about a 2011 Foster and Rahmstorf paper.
    http://www.realclimate.org/index.php/archives/2011/12/global-temperature-news/#more-10128

  39. 39
    Steve Fish says:

    I tried to post this and got a message to try again later-

    Regarding removing variability from the surface temperature record I remembered this RC post about a 2011 Foster and Rahmstorf paper.
    http://www.realclimate.org/index.php/archives/2011/12/global-temperature-news/#more-10128

  40. 40
    patrick says:

    @6 > @5 (Russell) Stephan Lewandowsy:

    The reason it may seem to escape you is that it is purely innuendo, and your interest is clarity, I think.

    The innuendo implies that there is a continuity between “antiwar, antinuclear, and alternative energy activism” (“of earlier decades”) and the work that is the subject of this post.

    The innuendo gets worse–and more devious–from there. It is a purely rhetorical argument, and without substance, I think.

    Thank you to the authors for their work; for clearly explaining it; for posting on it here; and for responding to some comments.

    The “linguistic landscape created by denial” is something I particularly recognize, and it’s a descriptor that is particularly memorable [Ref.5]: http://dx.doi.org/10.1016/j.gloenvcha.2015.02.013

    The “Scientific Certainty Argumentation Methods” (SCAMs) noted there (from Freundenburg et al., 2008) serves as a great pathfinder through the landscape created by denial. It’s a great reminder of where we are–or have been. And it keeps clear what is meant by “certainty” and “proof.”

    http://onlinelibrary.wiley.com/doi/10.1111/j.1475-682X.2008.00219.x/abstract

  41. 41

    CH at 30–I get that a lot, too

    RC at 33: That whole “30 years to make climate” is absurd. It takes perhaps one year (one could say one minute), if one has all the data.

    BPL: Please read:

    http://bartonlevenson.com/30Years.html

  42. 42
    Dean says:

    To Chuck Hughes, #28, regarding reading comprehension. I think that surveys have shown that the most ardent deniers are not low information types. They read a lot and tend to have university degrees. In fact, I think the same has been shown for conspiracy theorists in general, and recently for vaccine doubters too. I saw about a book that looked at the history of wild conspiracy theories in US history. We appear to have a cultural proclivity for believing such things in the United States. Maybe it is a cultural distrust of authority, which would seem to not just be political authority, but information experts.

  43. 43

    @40: Connecting to the SCAM reference, there is now quite a bit of work on the normative implications of uncertainty–which are quite the opposite of SCAMs. The most recent public writing is here: http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/dec/01/uncertainty-is-exxons-friend-but-its-not-ours

    There is an entire issue of the Philosophical Transactions dedicated to this issue here: http://rsta.royalsocietypublishing.org/content/373/2055.

    For specific key papers I would recommend:

    Lewandowsky, S.; Risbey, J. S.; Smithson, M.; Newell, B. R. & Hunter, J. Scientific uncertainty and climate change: Part I. Uncertainty and unabated emissions Climatic Change, 2014, 124, 21-37, doi: 10.1007/s10584-014-1082-7

    Lewandowsky, S.; Risbey, J. S.; Smithson, M. & Newell, B. R. Scientific uncertainty and climate change: Part II. Uncertainty and mitigation Climatic Change, 2014, 124, 39-52, doi: 10.1007/s10584-014-1083-6

    Freeman, M. C.; Wagner, G. & Zeckhauser, R. J. Climate sensitivity uncertainty: when is good news bad? Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, 2015, 373, doi: 10.1098/rsta.2015.0092

  44. 44
    Hank Roberts says:

    Dean says: … I think that surveys have shown …. In fact, I think …. I saw about a book ….

    Well, that settles that.

    Oh wait. Can you check what you think you remember somehow?

  45. 45
    Chuck Hughes says:

    We appear to have a cultural proclivity for believing such things in the United States. Maybe it is a cultural distrust of authority, which would seem to not just be political authority, but information experts.

    Comment by Dean — 1 Dec 2015 @

    However you want to slice it there’s a disconnect between the public and the scientific community. I know science teachers who don’t trust their own profession. It’s ignorance and absurd belief mixed with some sort of political ideology. At least is is where I live.

  46. 46
  47. 47
    patrick says:

    @43 Stephan Lewandowsky:

    I was thinking that SCAMs are a fallacy of argument that might be called “the appeal to uncertainty.” I see that you’ve used similar language in the most recent public writing, which you link. [“Appeals to uncertainty to delay or preclude…action…”]

    The article (Dec 1), including all the text links you provide, is a book in itself–on climate science, the uses and abuses of uncertainty, the inhibition of the creativity that is necessary for solutions in a crisis, misguided zeal, and a lot more.

    Your article is a great contribution to public understanding. Thank you very much.

  48. 48
    Dan H. says:

    Whether one uses the term “pause” or some other terminology is not the point. The main focus is the lower temperature rise over the 15-year period from 1998-2012, as compared to previous time frames. From the IPCC, the warming over the 15-year period, a.k.a. “this hiatus” was only 0.04C/decade, compared to 0.11C/decade over the previous 60 years, and much lower than the 0.23C/decade from 1979-1998.

    http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter09.pdf

    Yes, this was a short-term change. Just like the increase starting in 1980 was a short-term change. The long-term trend remains fairly constant, with many fluctuations, and has not deviated from about 0.6C/century. Too much is being made of recent hot and cold years. These are simple weather fluctuations, and too much is being made of these individual changes. Does the multi-year increase in Arctic sea ice indicate that the long-term reduction has halted, and the sea ice extent will return to the large expanses of 1979?

  49. 49
    Russell says:

    13
    Stephan Lewandowsky asks about surveys designe to measure :” whether any hiatus or sociological discontinuity in fact exists between the collective antiwar, antinuclear, and alternative energy activism of earlier decades, and that of today ? ”

    “How would continuity be manifest? And in what way could it be discontinuous?

    One metric could be the overlap of authorship of highly publicized papers in past climate science controversies with subsequent eminence in academic or organizational politics .
    A fascinating article touching on this recently appeared in the behavioral psycology literature:
    Political diversity will improve social psychological scienceJosé L. Duarte,Jarret T. Crawford,Charlotta Stern,Jonathan Haidt,Lee Jussim and Philip E. Tetlock (2015).
    Behavioral and Brain Sciences, “>Volume 38, January 2015e130
    http://journals.cambridge.org/action/displayAbstract?aid=9945982

  50. 50
    Hank Roberts says:

    > Dan H

    Yes, friends, you heard it here first:

    The Bore Hole « RealClimate
    http://www.realclimate.org/index.php/…/comment-page-15/?...
    RealClimate
    Dec 6, 2004 – Dan H. says: … Using the entire dataset (from 1880), the short-term trend has fluctuated significantly, but the long-term trend has not deviated …


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