Satellite-Era SST Anomalies: Models Vs Observations Using Time-Series Graphs And 17-Year Trends


This post presents observed 17-year (204-month) Sea Surface Temperature (SST) anomaly trends versus those of the climate models from the IPCC AR4, and presents it as the casual observer would look at it in terms of how well the models portray sea surface temperatures during the last 30 years, which is the satellite era of Sea Surface Temperature data.

This is a post about perceptions, about what the casual observer would perceive if he or she were to investigate the data.


The first post here to use 17-year trends, 17-Year And 30-Year Trends In Sea Surface Temperature Anomalies: The Differences Between Observed And IPCC AR4 Climate Models, received a good amount of attention. Roger Pielke Sr prepared a post about it, and Anthony Watts cross posted it at WattsUpWithThat. The “17-year and 30-year trend post” showed how poorly the IPCC AR4 climate models hindcast and projected the most recent 17-year and 30-year trends in Global and Hemispheric Sea Surface Temperature anomalies. But the graphs also presented the multidecadal variations in trends for the model mean and observation-based data since 1900. This generated a post from Tamino, over at his blog Open Mind. Maybe Tamino was not aware that the vast majority of the readers here understand that a model mean would average out any multidecadal variations in the individual model runs, if any existed. And maybe Tamino was not aware that the readers here also understand that very few of the models included in the IPCC AR4 model mean actually have multidecadal variations, because we have presented and discussed this, and the reasons for it, in earlier posts and comments. Yet another example of this was presented in the reply post to Tamino. Regardless of whether Tamino was aware, it still appears his post was solely intended to distract his readers from the conclusions of the “17-year and 30-year trend post,” which were summarized in Table 1.

This post presents time-series graphs that compare Global and Hemispheric satellite-era Sea Surface Temperature anomalies to the model mean of the hindcasts and projections of the AR4 climate models. Time-series graphs and linear trends are easy to understand. They are used and discussed quite frequently here. Like the “17-year and 30-year trend post”, 204-month (17-year) linear trends are used. The choice of 204-months (17-years) is based on the Santer et al (2011) paper, Separating Signal and Noise in Atmospheric Temperature Change: The Importance of Timescale. In the abstract, Santer et al (2011) conclude with:

“Our results show that temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature.”

Since Sea Surface Temperature anomalies are not as noisy as Lower Troposphere Temperature anomalies, we’ll assume that 17 years would also be an acceptable timescale to present sea surface temperature trends on global and hemispheric bases.

The satellite era of Sea Surface Temperature observations is only 30 years old, so we’ll use a relatively simple presentation. We’ll look at the linear trends of the models and observations on Global, Northern Hemisphere, and Southern Hemisphere bases for the first 17 years of the data and the last 17 year of data. This will show how well (or poorly) the linear trends of the IPCC AR4 model hindcasts and projections matched the trends of the observation-based data during these two periods. The results may surprise some of you.


1. The dataset used for observations is Reynolds OI.v2 Sea Surface Temperature data.

2. This post does not provide statistical analyses like you might find at Lucia’s The Blackboard.Only the data and the linear trends are presented. Anyone is welcome to carry the analyses further.

3. Each of the of the graphs presents all of the observed and model Sea Surface data, from 1982 to present, even though the trends for 204-months are being illustrated. The unused data is shown as dashed lines.

4. The two periods presented in the post share a common factor: the 1997/98 El Niño. This El Niño event was described as the El Niño of the century due to its strength. It was massive on all accounts, and is plainly visible in the graphs of both periods. The 1997/98 El Niño makes its presence known in the data toward the end of the first 204-month period, which runs from January 1982 to December 1998, and toward the beginning of the second period, which runs from November 1994 to October 2011. This will undoubtedly be raised in some of your comments.


Figure 1 compares the trends Global Sea Surface Temperature anomaly observations for the first 17-year period to the trends of the IPCC AR4 Model Mean. Not too surprisingly, the two trends are relatively close. The trend of the observed Global Sea Surface Temperature anomalies is approximately 0.123 deg C per decade, while the hindcast and projection of the models present a trend of 0.115 deg C per decade. The trend of the observations is only 7% higher than the model trend. Not bad. The model trend actually appears conservative during this period.

Figure 1

Unfortunately for the models, during the last 17-year period, Figure 2, the rise in observed global sea surface temperature anomalies (0.04 deg C per decade) is only 26% of the rise projected by the models (0.155 deg per decade). That’s not too good when we consider the rise in Sea Surface Temperature is supposed to be forced by Anthropogenic Greenhouse Gases and that the model mean is supposed to represent the forced component of the all of the models, without the noise caused by the internal variability inherent in the individual model ensemble members.

Figure 2


Figure 3 compares the observed trend versus the model mean trend for the Sea Surface Temperature anomalies of the Northern Hemisphere for the initial 17-year period. The observed trend from 1982 through 1988 (0.198 deg C per decade) is about 55% higher than that hindcast and projected by the models (0.128 deg C per decade). But during the last 17 years, Figure 4, the observed trend (0.061 deg C per decade) is 64% lower than the trend of the model mean (0.171 deg C per decade). In other words, the trend of the model mean was too low during the first 17 years of this 30-year Sea Surface Temperature dataset and way too high during the last 17 years.

Figure 3


Figure 4


The problems for the climate models persist, as one would expect, in the Southern Hemisphere. For the first 17-year period, Figure 5, the observed trend in Southern Hemisphere Sea Surface Temperature anomalies (0.065 deg C per decade) is 62% of the trend hindcast and projected by the model mean (0.105 deg C per decade). And it gets even worse. The trend of the observed rise in Sea Surface Temperature anomalies during the last 17 years of the Southern Hemisphere (0.025 deg C per decade) is only 17% of the trend that was hindcast and projected by the models. In other words, for the oceans of the Southern Hemisphere, which represent about 40% of the surface area of the globe, the linear trend of the Sea Surface Temperature anomalies that was hindcast and projected by the models is more than 5 times higher than what was observed. More than 5 times. Let’s try it one more time; the average of all of the climate models used in the IPCC AR4 have projected Sea Surface Temperature trends that are more than 5 times higher than what has been experienced in the Southern Hemisphere, or 40% of the surface area of the globe, for the last 17 years.

Figure 5


Figure 6


So what impression is the casual observer left with if he or she were to investigate how well climate models can hindcast and project sea surface temperatures over 17-year periods, a time span that is appears to be acceptable to the who’s-who of climate scientists that helped prepare the Santer et al (2011) paper? Not a very good impression. They can see that the observed Sea Surface Temperature trends and those projected by the climate models only appear to come close to matching one another on a global basis, but that the match is only good for the first 17-year period of the satellite-era Sea Surface Temperature data. They can see that the models do not come close to matching observations in either hemisphere during the first or last 17-year periods.

The casual observer may investigate further and discover explanations for the poor behavior of the models, such as the models don’t do a good job of reproducing natural variability, and the models aren’t initialized to reproduce the multidecadal variations observed in the surface temperature record, and the like. And do you know what those explanations sound like to the casual observer? Excuses. And do you know what they sound like to a not-so-casual observer, like me? Excuses.


Both the Reynolds OI.v2 Sea Surface Temperature data and the IPCC AR4 Hindcast/Projection (TOS) data used in this post are available through the KNMI Climate Explorer. The HADISST data is found at the Monthly observations webpage, and the model mean data is found at the Monthly CMIP3+ scenario runswebpage.

ABOUT: Bob Tisdale – Climate Observations

About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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14 Responses to Satellite-Era SST Anomalies: Models Vs Observations Using Time-Series Graphs And 17-Year Trends

  1. Pingback: Another Excellent, Well-Explained Post By Bob Tisdale Titled “Satellite-Era SST Anomalies: Models Vs Observations Using Time-Series Graphs And 17-Year Trends” | Climate Science: Roger Pielke Sr.

  2. ferd berple says:

    Doesn’t this puts the lie to the notion that the models have not been initialized? In which case they are simply curve fitting, and a poor example at that.

    5066.txt Hegerl:

    [IPCC AR5 models]

    So using the 20th c for tuning is just doing what some people have long
    suspected us of doing […] and what the nonpublished diagram from NCAR showing
    correlation between aerosol forcing and sensitivity also suggested.
    Should we ask to admit in their submission what variables were
    considered when tuning, and if any climate
    change data were considered and at what temporal and spatial
    representation (global mean trend?),
    and advise that we will not be able to use those models for any future
    attribution diagrams? That would at least lay it in the open…


  3. Seawater is difficult to warm up from the surface. Conducting the heat deep down is not efficient on most places. Because of the obsession with ”anthropogenic” the real problems / offenders are completely overlooked: by population increase, so is oils and fats discharge into the sea.

    No matter if is virgin olive oil, chicken, pork, beef fat, industrial oils. They spread on the top of the seawater – take long time to brake down. Those oils decrease evaporation – evaporation is cooling process. 2] less evaporation = less rainfall – rainfall cools the sea + less clouds as sun-umbrella. 3] because of the obsession to blame CO2 – is disregarded that: when the tectonic plates are more active; more submarine volcanoes + hot vents are more active – as it is the case now. All the heat, 100% of it is absorbed by the water and distributed by currents = warmer seawater.

    I consider: anthropogenic is not only for misleading; but very destructive for everything normal: I have being aggressively silenced for proving that CO2 fear is a con. In the process, because of those oils / fats; the water is getting depleted of oxygen; not suffusion to sustain most variety of fish for big part of the year – putting all the blame on the fishermen will not solve the problem. I am asking you all concerned people; to help me present the truth – lots of damages can be minimised Until then,.all the damages will be pined on the Warmist scientists / activist. Skeptics are obsessed about the money squandered; but not even familiar about the many destructive attitudes of the propaganda machine… .

  4. Pascvaks says:

    When climate simulations cannot be shown to replicate the past they are of no value whatsoever in convincing anyone with an open mind about their utility for future projections. Climatology computer simulation designers and engineers would be wise to master the 20th Century, and then the next future decade, before attempting a high wire 21st Century act without a net again any time soon. You have made many small-minded vindictive enemies, but many more trust in your integrity than you know.

  5. Pingback: The IPCC Says, “The Observed Patterns of Warming…, And Their Changes Over Time, Are Only Simulated By Models That Include Anthropogenic Forcing” | Bob Tisdale – Climate Observations

  6. George says:

    Part of what I find so aggravating is when people attempt to create linear trends from data that actually appears to make pretty clear step changes and then present a hypothesis that would account for a linear trend, but the data aren’t trending linearly.

    In figure 6 the dotted blue line and early portion of the solid blue prior to 1997 seems to trend pretty flat in my uncalibrated eyeballing of it. Then if you look at the solid blue from about 1999, that also seems to trend pretty flat.

    I don’t believe that gradually increasing CO2 in a fairly linear fashion over time will result in these step changes. So they apply a linear trend to the data which more closely approximates the more gradual increase in CO2 and attempt to model that because it would validate their hypothesis. But since that is NOT what appears to be actually happening in nature, their model hindcasts and forecasts break down the father back or forward in time you go.

    You have pointed out these step changes before in your sea surface diagrams and Judith Curry has pointed it out in the land ground temperature data. These steps seem to coincide with large El Nino events but whether we will see such a step change after the 2010 event remains to be seen. So far it looks like the answer to that one is “no”. In fact, there could be an argument that global temperatures have been trending down in their peaks since 1998 but possibly flat in their mean. The proof of that pudding will come in the next 5-10 years.

    I still don’t think they have hit on what is causing changes in climate that we see on a decadal scale and I believe their CO2 hypothesis will have a much smaller impact than they believe it has.

  7. Chas says:

    Bob , I dont know if you have seen Isaac Held’s reply to ‘AJ’ at the bottom of
    If I understand this comment correctly, some of the models used for AR5 will have initialised ocean states.
    BTW Have you come across Andrew Wittenberg’s 2000-year long control runs, anywhere? – I wonder if they could shed some light on the impact of enso on global temperatures.
    The runs are discussed, a bit, in:

  8. Bob Tisdale says:

    Chas: Thanks for the link to Isaac Held’s reply to AJ. I missed that post completely. I’ll have to read it when I take a break from what I’ve been up to. And no, I have not come across Andrew Wittenberg’s 2000-year long control runs. Have you tried emailing him? Most climate scientists that I’ve communicated with via email have been very helpful.


  9. Pingback: On the SkepticalScience Post “Pielke Sr. Misinforms High School Students” | Bob Tisdale – Climate Observations

  10. Pingback: Tisdale schools the website “Skeptical Science” on CO2 obsession | Watts Up With That?

  11. Pingback: Do Climate Models Confirm Or Contradict The Hypothesis of Anthropogenic Global Warming? – Part 1 | Bob Tisdale – Climate Observations

  12. Pingback: It Really Should Go Without Saying, BUT… | Bob Tisdale – Climate Observations

  13. Pingback: What Do Observed Sea Surface Temperature Anomalies and Climate Models Have In Common Over The Past 17 Years? | Bob Tisdale – Climate Observations

  14. Pingback: Tisdale on the “17 year itch” – Yes, there is a Santer clause | Watts Up With That?

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