This is a discussion of the criticisms by the blogger Tamino about a couple of my recent posts. Tamino’s unjustified complaints were about my graphs of the divergence between the National Oceanographic Data Center (NODC) ARGO-era (2003 to present) Global Ocean Heat Content (OHC) data for the depths of 0 to 700 meters and the Goddard Institute for Space Studies (GISS) climate model projections/predictions for that Global OHC data.
This is a long post, almost 6,000 words. So I’ve included a summary at the beginning of this post, immediately after the introduction. Readers can then continue to read the rest if they chose. The headings of discussions are bold faced and many of the illustrations are annotated so they can scroll down through the headings to find a topic, if they have questions about specifics.
Not surprisingly, Tamino has one again disagreed with something I presented in a couple of my posts and has attempted to dispute it. This time he has responded to my recent First-Quarter 2011 Update Of NODC Ocean Heat Content (0-700Meters) post that was cross posted at WUWT as The GISS divergence problem: Ocean Heat Content. There Anthony Watts provided an introduction.
Tamino’s disciples were much impressed with his presentation and added their OpenMind-prompted beliefs to the WattsUpWithThat thread. Please take a few moments to read Tamino’s response Favorite Denier Tricks, or How to Hide the Incline.
Let’s see where Tamino misses the mark this time.
Tamino failed in his efforts to discredit me, my simple model-data comparison graphs of Global Ocean Heat Content, and the posts that include those graphs.
Tamino failed to prove the start year of 2003 was cherry picked to provide the lowest trend. I first started posting those model-data comparison graphs with the earlier version of the OHC data. With that earlier version, 2003 did not provide the lowest trend, as it does now. So my first uses of 2003 as the start year for those graphs were not dependant on 2003 being the year that provided the lowest trend. NODC corrected and revised their OHC data in October 2010. Since that NODC update, 2003 has produced a low trend. On one hand, Tamino may not have known about the NODC’s October 2010 changes to the OHC data, but he should read a post in its entirety before accusing someone of using data manipulation tricks. In the more recent of my posts that Tamino had referred to, I had noted that there had been recent changes to the data and I provided links to the source and to my past posts that discussed those changes. So, on the other hand, Tamino also may actually have known about those changes to the NODC OHC data and ignored their impacts.
Tamino failed in that effort also because he chose not to believe what I had written, which was that I had used the start year of 2003 since that was the year ARGO observations became the dominant source of OHC data observations. I had other reasons that had gone unwritten in my two recent posts. One was obvious: the data has been flat since 2003. That fact is tough to miss. The other may not have been obvious: the continued use of 2003 allowed the start date to remain consistent with the same model-data comparison graphs in earlier posts at my blog and consistent with discussions at Roger PIelke Sr.’s website.
Tamino failed to prove that I had misrepresented the GISS model trends, which he had described as, “a blatant falsification of what the GISS prediction is.” First, he did not present the GISS prediction in his graphs; he shifted subjects so quickly that many of his readers may not have noticed. And based on the comical choice of words used by Tamino’s disciples in their comments on the WUWT thread (misuse, misleading, dishonestly, etc.), I have to believe that that was the case. Specifically, Tamino changed from a discussion of model trends to a discussion of observational data trends during a warming period beforethe ARGO era. Second, Tamino then attempted to illustrate the point at which that data-based (not model-based) trend intersects with the ARGO-era data as the “honest method,” but since he wasn’t using model-based trends, his efforts were for naught. Third, his “honest method” did not consider the differences between a model-based trend and the data-based trend that Tamino chose to present. The point at which the model-based trend intersects with the ARGO-era OHC data is impacted by the revision level of the data and by the base years that GISS elects to use in their presentations of the models.
I discuss and illustrate all of those failures in Tamino’s post in the following. I’ve even tacked on an additional discussion after discovering another reference to my OHC posts in Tamino’s follow-up post Five Years.
This is the dataset introduction that appears in the most recent of the posts that Tamino referred to. It was the one cross posted at WUWT on Sunday, May 8, 2011.
The NODC OHC dataset is based on the Levitus et al (2009) paper “Global ocean heat content(1955-2008) in light of recent instrumentation problems”, Geophysical Research Letters. Refer to Manuscript. It was revised in 2010 as noted in the October 18, 2010 post Update And Changes To NODC Ocean Heat Content Data. As described in the NODC’s explanation of ocean heat content (OHC) data changes, the changes result from “data additions and data quality control,” from a switch in base climatology, and from revised Expendable Bathythermograph (XBT) bias calculations.
I POSTED GRAPHS OF QUARTERLY DATA BUT TAMINO’S GRAPHS ARE OF ANNUAL DATA FROM AN EARLIER POST
Readers who are observant will have noted that Tamino has shifted the presentation of the data from quarterly to annual. This discussion is provided simply to reduce any confusion that may have caused.
Tamino writes as an introduction:
WUWT has a post by Bob Tisdale, based on one of Tisdale’s own posts. The theme is that ocean heat content (OHC) hasn’t risen as fast as GISS model projections. Watts even says “we have a GISS miss by a country mile.” But Tisdale can only support his claim by using tricks to hide the incline. In fact he uses two of the favorite tricks of deniers. One is a clever, but hardly new, trick called “cherry picking.” The other is ridiculously simple: misrepresentation.
My most recent OHC post First-Quarter 2011 Update Of NODC Ocean Heat Content (0-700Meters) is a very simple post that advises readers that the NODC has posted its 1st quarter 2011 OHC data. Anthony Watts wrote a brief introduction and cross posted it at WUWT. My “First-Quarter post” is not based on the older post, ARGO-Era NODC Ocean Heat Content Data (0-700 Meters) Through December 2010,which Tamino cites; it is a separate post. I referred to the “ARGO-era post” in the “First-Quarter post”, but it is not based on the “ARGO-era post”. One very obvious difference: in the “First-Quarter post”, the model-data comparison was presented on a quarterly basis. Refer to Figure 1.
But the data in the graph that Tamino elected to discuss was presented annually. It’s Figure 2 from my “ARGO-era post”, which I’ve included here as Figure 2.
It must have been easier for Tamino to use annual data for the rest of his failed critique. So I’ll use the annual data throughout the rest of this discussion so that the graphs and discussions agree with Tamino’s post and his graphs.
OPENING NOTES ABOUT THE GRAPHS
Figures 1 and 2 are simple graphs. Starting in 2003, they show the projections of GISS climate model outputs with global ocean heat content rising at a rate of 0.7*10^22 Joules, and they show the observed variations in global ocean heat content data as determined by the NODC. One graph presents the data on an annual basis, and the other, on a quarterly basis, which is the period chosen by the NODC for the delivery of their OHC product. I’ve had EXCEL determine the linear trends for the observations and provide the corresponding equations. Based on those linear trends, the quarterly data, Figure 1, shows that Global OHC is rising at a rate of 0.077*10^22 Joules per year, and the annual data, Figure 2, shows a rate of 0.05*10^22 Joules per year. Since Tamino chose to present annual data, let’s discuss it. The GISS projection is rising at a rate that’s about 14 times higher that the observed rate, or the observations are rising at a rate that’s approximately 7% of the rise projected by GISS.
In the “First quarter post”, I wrote about the graph that appears here as Figure 1:
Looking at the NODC OHC data during the ARGO era (2003 to present), Figure , the uptick was nowhere close to what would be required to bring the Global Ocean Heat Content back into line with GISS projections.
There was nothing misleading in that statement. And in the “ARGO-era post”, I first discussed why I was lowering the GISS projection from 0.98*10^22 Joules per year to 0.7*10^22 Joules per year, and the sources of both projections. I wrote about Figure 2:
The GISS projection of 0.7*10^22 Joules per year dwarfs the linear trend of the ARGO-era NODC OHC data. No surprise there.
There was no surprise for me or for those who have read my earlier OHC posts that have included similar graphs, since I’ve been posting the OHC model-data comparisons since October 2009.
I did not state that these graphs falsified the models. Eight years of data is way too short for that. In his introduction of the most recent post, Anthony Watts did not state the graphs falsified the models. Yet the appearance of the graphs in the posts prompted Tamino and his followers to characterize those graphs with terms such as…
CHERRY PICKING AND MISREPRESENTATION?
In his opening salvo, Tamino accused me of cherry picking and misrepresenting the Ocean Heat Content data. He apparently doesn’t believe the basis for the start year of 2003 or understand the short history of my graph that compares the GISS climate model projections and the OHC data. And his accusation of misrepresentation is unfounded as we will see.
TAMINO’S ACCUSATION OF CHERRY PICKING
On cherry picking, Tamino writes and includes a quote from my “ARGO era” post:
Why does Tisdale give such a different impression? First let’s expose the cherry-picking part. To make it look as though observation is out of whack with prediction, Tisdale starts with 2003. His justification is to call this the “Argo-era,” which he claims he chose because
According to it, ARGO floats have been in use since the early 1990s, but they had very limited use until the late 1990s. ARGO use began to rise then, and in 2003, ARGO-based temperature readings at depth became dominant. Based on that, I’ll use January 2003 as the start month for the “ARGO-era” in this post.
I don’t believe him.
The fact is, I needed a start date for that post about ARGO-era data, a post that illustrated much more than the model-data graph. By 2003, ARGO buoys provided a significant contribution to the observations used in the calculation of Global OHC. The use of the word dominant, looking back at the “ARGO-ear post”, was an exaggeration. ARGO floats provided a significant contribution by 2003, not only by the number of samples, but by greatly increasing the spatial coverage of Southern Hemisphere waters.
Back to the discussion of cherry picking…
I explained why I selected 2003, and Tamino wrote, “I don’t believe him.” Tamino elected not to believe. His beliefs are his choice and they are not evidence of cherry picking on my part.
Tamino attempted to reinforce his belief by showing that 2003 would have had the lowest trend. I’ll agree with one point: a trend from 2003 to 2010 as the data currently existsdoes have a lower trend than trends that run from 2002 to 2010 or from 2004 to 2010, but…
2003 DIDN’T ALWAYS PROVIDE THE LOWEST TREND FOR A SHORT-TERM OHC GRAPH
In the “First-Quarter 2011 Update” post, I included an introduction to the NODC OHC dataset. In part, it reads:
It [the NODC OHC data] was revised in 2010 as noted in the October 18, 2010 post Update And Changes To NODC Ocean Heat Content Data. As described in the NODC’s explanation of ocean heat content (OHC) data changes, the changes result from “data additions and data quality control,” from a switch in base climatology, and from revised Expendable Bathythermograph (XBT) bias calculations.
The 2010 update and changes had a significant impact on the short-term, ARGO-era OHC data. Figure 3 illustrates the 2009 version of the NODC OHC data and the 2009 version with the 2010 revisions. Both start in 2003 and have the 2003 values zeroed to help show the differences during the ARGO era. As described above, I started presenting the graph of OHC data versus GISS model projection back in 2009. The 2009 version of the Levitus et al data would clearly have had a negative trend if 2004 was selected as the base year, so 2003 would NOT have been the “cherry year” for that version.
Based on what has been presented so far, Tamino has not proven his claim that I had cherry picked the start year of 2003, basically because it wasn’t the ideal year to start a trend (one that contradicts the models) when I had first started presenting those OHC model-data comparisons.
Note: Another of the basic intents of presenting the data with the start year of 2003 is to show how flat the data has been since then. I’m not sure why that’s so difficult to grasp. There was a significant rise in Global OHC from 2001 to 2003, Figure 4, and since then, the OHC data has been reasonably flat, far short of the linear trend projected by GISS. And as illustrated in the Update And Changes To NODC Ocean Heat Content Dataand the “ARGO-era post”, the flattening is primarily the result of the significant decreases in North Atlantic and South Pacific OHC.
Using 2003 as a start year for my “ARGO-era post” also allowed that post to remain consistent with past OHC posts at my blog and with posts by Roger Pielke, Sr.
ROGER PIELKE, SR’s LITMUS TEST FOR GLOBAL WARMING
Since 2007, Roger Pielke Sr. has been recommending that OHC be used as A Litmus Test For Global Warming – A Much Overdue Requirementand recommending that OHC model projections be compared to OHC observations. In that 2007 post, he recommended that the comparison be communicated each year if not more often. He used 2003 as the start date for his “litmus test”. Roger Pielke Sr. discussed the subject again in his February 9, 2009 post Update On A Comparison Of Upper Ocean Heat Content Changes With The GISS Model Predictions. In it, he compared annual observation values to GISS projections, starting in 2003. Those projections were based on the response by James Hansen of GISS. Pielke Sr. concludes that post with:
While the time period for this descrepancy with the GISS model is relatively short, the question should be asked as to the number of years required to reject this model as having global warming predictive skill, if this large difference between the observations and the GISS model persists.
And through 2010, the “large difference between the observations and the GISS model” has persisted. To avoid the controversy in the future, maybe I simply need to add a note to the graph, one that reads to the effect of “If ARGO-Era OHC Observations Continue To Run Far Below Model Projections, How Many Years Are Needed To Reject The Models?”
Since no one else was illustrating the difference between OHC observations and the GISS model projections on a regular basis, I began including the graph in many of my OHC posts. I believe my October 16, 2009 post NODC Ocean Heat Content (0-700 Meters) Versus GISS Projections (Corrected) was my first OHC post to include it. Shortly after that, I went into great detail to illustrate and discuss Why OHC Observations (0-700m) Are Diverging From GISS Projections.
I ACTUALLY LOWERED THE GISS PROJECTION RECENTLY
In the “ARGO-era post”, I lowered the GISS projection from 0.98*10^22 Joules per year (which was based on Pielke Sr’s discussion of the Hansen response) to 0.7*10^22 Joules per year, so that the projections would fall in line with the recent RealClimate model-data comparisons. I wrote:
In past posts, when I’ve compared the NODC Global Ocean Heat Content to GISS projections, I’ve used the rate of 0.98*10^22 Joules per year for the GISS projection. This value was based on Roger Pielke Sr’s February 2009 post Update On A Comparison Of Upper Ocean Heat Content Changes With The GISS Model Predictions. The recent RealClimate posts Updates to model-data comparisons and 2010 updates to model-data comparisons have presented the projections based on Gavin Schmidt extending a linear trend of the GISS Model-ER simulations past 2003. The linear trends in both graphs are approximately 0.7*10^22 Joules per year. I’ll use this value in the comparison, but first a few more notes.
I used the 0.7*10^22 Joules per year trend again in my “First-Quarter 2011 Update” post (that’s the one that initiated the Tamino response), but I’m having second thoughts now. The difference between the RealClimate value and the “Hansen response/Pielke post” value of 0.98*10^22 Joules per year is curious, and will be the subject of a future post.
TAMINO FORGETS THE BASICS
In his post, Tamino writes:
Now let’s look at the misrepresentation — specifically a blatant falsification of what the GISS prediction is. I don’t know exactly what the GISS model prediction for OHCA is, neither does Tisdale, he just “eyeballed” it from the RealClimate graph…
Eyeballed? Reading a graph is a simple task one learns in grammar school. In my “ARGO-era post” I provided links to the RealClimate posts that compared model projections to observations. Here they are again: Updates to model-data comparisons and 2010 updates to model-data comparisons. They were the basis for the model projections I’ve used. Tamino also included the OHC comparison graph from the 2010 RealClimate update in his post and characterized it as, “an honestcomparison of these observations with prediction…” In Figure 5, I’ve thrown a few notes on the 2010 RealClimate graph to remind those who have forgotten how to read a graph. I hope I don’t have to provide a more detailed discussion than what’s shown on Figure 5. The result, as shown, is the linear extrapolation of the climate model ensemble mean has a trend of approximately 0.7*10^22 Joules per year.
THE CLAIMED MISREPRESENTATION
I stopped the Tamino quote above in mid-paragraph. Here it is in its entirety:
Now let’s look at the misrepresentation — specifically a blatant falsification of what the GISS prediction is. I don’t know exactly what the GISS model prediction for OHCA is, neither does Tisdale, he just “eyeballed” it from the RealClimate graph. But let’s look at what the prediction would be for a simple linear extrapolation. The RealClimate trend line starts about 1993, so let’s take the data from 1993 through 2002 and fit a straight line, then extend that line as a prediction through 2010. We’ll call it “prediction by extrapolation.” It guarantees that our prediction line will have the correct slope and intercept to match a true continuation of the trend. And it gives this:
If you weren’t paying attention, you may not have noticed what Tamino just did. Tamino switched from a discussion of the GISS model prediction to a discussion of the linear trend line of the OHC “data from 1993 through 2002”. I presented the Model Projection (prediction) in my post, and Tamino presented the linear trend of the OHC data(current version) in his. They are not the same.
Tamino’s first trend graph sparked my curiosity about a few things. The linear trend of the OHC data (current version) for the period Tamino elected to show (1993-2002) is about 0.58*10^22 Joules per year, which is below the model prediction of 0.7*10^22 Joules per year. Refer to Figure 6. And for comparison purposes, I’ve also included the data for an older version of the Levitus et al OHC data. The older data is still available through the NODC website at their Heat content 2004webpage. Not surprisingly (since the models would have been initially compared to earlier versions of the OHC data and tuned accordingly), the linear trend of the older OHC data (approximately 0.67*10^22 Joules per year) runs closer to the model prediction.
So far, I have not misrepresented the linear trend of the GISS model projection/prediction in any way. I also have not misrepresented the Levitus et al OHC data. Tamino’s claim of misrepresentation must come from something else. Maybe it’s the appearance of the graph?
WHERE THE MODEL PROJECTION INTERSECTS WITH THE OHC DATA
In his final three paragraphs, Tamino writes:
But Tisdale didn’t do that. He chose a slope to match his “eyeball” estimate of the trend line in the RealClimate graph, but chose the interceptto match 2003. He even states “Note that I’ve shifted the data down so that it starts at zero in 2003.” Let’s call that the “Tisdale method” and compare it to the honest method when extrapolating the trend line:
Sorry, Bob. When you try to match a line’s slope, but then shift that line upward, choosing the intercept deliberately to make the prediction look as bad as possible, that’s dishonest.
It’s also one of the most common tricks that many denialists have used to “hide the incline.” That, and cherry-picking, just might be their favorites.
I’ve included Tamino’s graph that includes the “Tisdale method” as Figure 7.
Apparently, Tamino believes that a comparison of the GISS model projection that intersects the OHC data midway between 2003 and 2010 would better represent the comparison. Refer to Figure 8. The linear trend of the model projection is still about 14 times higher than the linear trend of the ARGO-era (2003-2010) OHC observations.
Let’s take a look at a visual comparison of the graph Tamino finds offensive (Figure 2) and a graph that Tamino might not find offensive (Figure 10). Animation 1 is a .gif animation that shows the comparison graphs of the GISS Model Projection versus ARGO-era OHC Observations:
1. with the Ocean Heat Content Data and GISS Model Projection zeroed at 2003, and
2. with the GISS Model Projection Intersecting With The Data Midway Between 2003 and 2010
Both show that the GISS Model Projection is about 14 times higher than the NODC Global Ocean Heat Content Data.
THE “FIT” OF THE MODEL WITH OBSERVATIONS, OF COURSE, DEPENDS ON THE REV. LEVEL OF THE DATA AND ON THE BASE YEARS
This is a discussion of the model projection/prediction, not the linear trend of the data from 1993 to 2002 that was used by Tamino.
Figure 9 is the comparison of the 2009 version of the NODC OHC data and the GISS Model–ER from the RealClimate post Updates to model-data comparisons, Gavin Schmidt of GISS notes the following about the base years he used for the model data:
Note, that I’m not quite sure how this comparison should be baselined. The models are simply the difference from the control, while the observations are ‘as is’ from NOAA.
He further explains his baseline for the model data in his reply to blogger Chad. Refer to comment 188 and the reply at 29 Dec 2009 at 10:19 PM. With respect to OHC, his reply reads:
…for ocean heat content it is more important and I plotted the drift corrected values in the second figure. You still need to baseline things (as I did in figure 1, following IPCC), but I’m still not sure what the OHC data are anomalies with regard to, and so I haven’t done any more processing for that. As it stands the spread in the OHC numbers is related to absolute differences in total heat content over the 20th C – if you just wanted the change in heat content since the 1960s or something, the figure would be a little different.
In other words, the base years for the GISS model in Figure 9 were established by a complicated method. And if you were to read the Levituset al (2009), you’d discover that Gavin Schmidt is correct, determining what they had used for a climatology in that version was confusing. Note also that the presentation of the data in Figure 9 runs from 1955, the start of the NODC OHC dataset. The climate model is identified as the coupled GISS Model ER, with the “R” standing for Russell ocean.
In October 2010, the NODC revised and corrected its Ocean Heat Content data. As mentioned earlier, I discussed those changes in the post Update And Changes To NODC Ocean Heat Content Data. In addition to the changes to the ARGO-era data shown in Figure 3, the revisions and corrections lowered the overall global OHC trend by approximately 9%. That was a sizeable decrease, with most of it occurring in the Southern Hemisphere. If you were to compare the NODC OHC data in both of the RealClimate model-data updates, Figures 9 and 10, you’d notice they’re different (because of the corrections to the data between the two RealClimate posts).
Figure 10 is a similar comparison from the 2010 updates to model-data comparisons post at RealClimate. For it, Gavin Schmidt writes:
I am baselining all curves to the period 1975-1989, and using the 1993-2003 period to match the observational data sources a little more consistently.
You’ll note that the model ensemble members are more closely grouped in this presentation. In other words, the span of the ensemble members during the period of 1975-1989 is much smaller in the 2010 update than it was in the 2009 update. RealClimate has also excluded the data before 1970 in the 2010 update. It’s a cleaner presentation, even with addition of the Lyman et al (2010) data.
So far RealClimate has presented the OHC data and model outputs two ways, using different base years. Recall that between those two RealClimate posts, the NODC revised and corrected its OHC data. Now note where the linear extrapolations from the model means intersect the data in both RealClimate graphs. In Figure 9, it’s much closer to 2010 than in Figure 10. That should be due primarily to the significant revisions and corrections to the observations.
Figure 11 is yet another GISS model-data comparison. It is from a 2008 presentation by Gavin Schmidt of GISS. The graph can be found on page 8 of the .pdf file GISS ModelE: MAP Objectives and Results. I provided a link to this presentation in the “ARGO-era post,” for “those who might be concerned that extending the linear trend does not represent the actual model simulations.” One difference with this graph is the addition of the coupled GISS Model-EH, where “H” represents the HYCOM ocean model. The NODC OHC data has the hump from the 1970s to the 1980s, and based on the timing of this presentation, it should be the NODC OHC data based on Levitus et al 2005, linked earlier. That dataset ended in 2003, so Gavin Schmidt has tacked on a few more years of data. Notice the dashed lines from 2003 to 2004. A significant difference with this graph is the units. All of the data in this post so far has been presented in terms of 10^22 Joules. The units in Figure 11 are watt-years per square meter.
I’ve highlighted the 2003 OHC observation and the base years of 1955 to 1970. Why did Gavin Schmidt use 1955 to 1970? Using those base years for the models and the data allowed him to show that the two models “bracketed” the observations. Refer to his note at the bottom of the slide. But for the graph in Figure 10, he was “baselining all curves to the period 1975-1989, and using the 1993-2003 period to match the observational data sources a little more consistently.” So it’s apparently acceptable practice by climate scientists to adjust the data as one sees fit to present the effect one wishes to illustrate. It could be to bracket the observations or to “match” the observations.
In my simple model-data graphs, I elected to show the model projection intersecting at the beginning of the ARGO-era data instead of intersecting with it elsewhere. It was my choice. But let’s consider something else.
Notice also how the ensemble mean for the GISS Model-ER data LEADS the observations at 2003 in Figure 11. As noted earlier, the older version of the NODC Global OHC data (0-700meters) on an annual basis is still available through their website (older ), and, of course, so is the current version (current). We can change the base years of both versions to 1955-1970, the same base years used by Gavin Schmidt in his presentation and then plot both datasets. Refer to Figure 12. With those base years, would the GISS Model-ER data have intersected with the current version of the NODC OHC data during 2003 to 2010? No. In 2003, the older version of the OHC data lags the model data and the current version of the data lags the older version.
What can we conclude from this part of the discussion? The point at which the GISS model mean or its linear extrapolation intersects with the global OHC data depends on the version of the data and on the base years selected by those presenting the data, which depends on what the presenter wants to show. It also illustrates that my starting the GISS Model data at 2003 does not misrepresent the GISS projection.
Some readers might describe Tamino’s post as smoke and mirrors.
SPEAKING OF SMOKE AND MiRRORS
A last minute addition to the post: I just discovered Tamino’s follow-up post Five Years.
In fact I have a prediction: that Bob Tisdale will deny he meant what he meant with his deceptive graph tricks, instead he’ll plead that he was just talking about the “trend” since 2003. Yeah … since 2003.
It’s all smoke and mirrors.
No. I haven’t lost sight of the fact that the graphs that Tamino finds so offensive show the observations have been relatively flat since 2003, a period I have described as the ARGO era. And since the model projection does not flatten, the observations are diverging from the GISS Model Projection. We can illustrate this another way. We can subtract the observations from the Model projections, Figure 13. Because the observations are so flat during that period, we can show that the difference between the model projections and observations are growing almost as fast as the model projections.
Tamino then discusses why he is smoothing the datasets with 5-year time spans. Later, in his reply to a blogger’s comment at May 10, 2011 at 5:16 am, Tamino describes how he’s smoothed the data:
[T]he data points are successive non-overlapping 5-year means — about as simple as it gets. The smoothed curves are a lowess smooth of the original data.
Tamino also throws in another remark that refers to Anthony Watts and me while he’s discussing his Ocean Heat Content graph:
Let Bob Tisdale and Anthony Watts focus on too-too-short time scales — when you look at the big picture, again the trend is clear. Upward.
For those who are trying to figure out what Tamino has done to the data in those graphs, let me explain it in more detail. With the Ocean Heat Content anomalies, he’s averaged the data from 1955 to 1959 and shown it as a 1957 data point. The next data point is five years later, 1962, and it represents the average of the OHC data from 1960 to 1964, and so on. And between the 5-year data points, there are straight lines. I’ve reproduced Tamino’s 5-year span filter in Figure 14, and added the original OHC data. I’ve also highlighted the years with the data points. As noted on the graph, Tamino’s method samples 5-year averages on 5-year intervals. But don’t the 5-year averages of the years between those 5-year intervals have any significance? Why not sample those as well? Why not utilize a more commonly used smoothing method: a 5-year running-mean (running-average) filter? Tamino has used running-mean filters in earlier posts. GISS uses a 5-year running-mean in their presentation of annual data on their Graphs webpage.
Why didn’t Tamino present the data smoothed with the more commonly used 5-year running-average filter? Because the data that’s been smoothed with a 5-year running-average filter, as shown in Figure 15, flattens in recent years.
The Ocean Heat Content data is not a noisy as the other datasets Tamino presented in that post, so he probably could have used a 3-year running-mean filter, Figure 16. But that would have extended the relatively flat period back to 2003.
Tamino’s graphs show what he wants to show. My graphs show what I want to show. As Richard M wrote in his May 10, 2011 at 4:06 pmcomment on the WUWT thread, “Looks to me like this debate is much ado about nothing. Both views are reasonable approaches. Neither one is clearly right or wrong, they are just different ways of looking at the data.” As far as I’m concerned, that comment is applicable to Tamino’s “Five years post”, too.
A TOPIC FOR A FUTURE POST
I had wanted to discuss the difference between the two GISS projections. For the last two OHC posts, I have used the projection trend that’s illustrated in the RealClimate model-data posts of 0.7*10^22 Joules per year. Before that I had used the trend of 0.98*10^22 Joules per year from the Hansen response and Pielke Sr. post. But this post is much too long to start a new discussion, so I’ll save it for a future post.
I will, however, show both model-projection trends in a final model-data comparison graph, Figure 17. Note the question I’ve added to it. It implies that I understand the period is too short to disprove the climate models, but it also reinforces that observations are rising at a rate that is significantly less than model projections during the ARGO era.
I abstained from responding to the unwarranted comments from Tamino’s disciples on the The GISS divergence problem: Ocean Heat Content thread at WUWT. I felt it was more important to document and illustrate where Tamino’s critique failed. But many persons did take the time to reply to Tamino’s followers, so to them, I’d like to say thanks.