![image42[1]](http://wattsupwiththat.files.wordpress.com/2014/05/image421.png?quality=75)
By Paul Homewood A guest post earlier today by David Dohbro, comparing satellite and surface temperature datasets, appears to have attracted a certain amount of criticism, not least because it has tried to compare anomalies based on different baselines. This is an update to that analysis.
To get around this issue, I am posting a comparison of GISS surface temperatures and RSS satellite numbers, both based on a baseline of 1979-98, which is the one used by RSS. (GISS still use 1951-80).
This change of baseline means that all GISS temperatures anomalies are reduced by 0.28C.
The graph below shows the GISS minus RSS temperature anomalies from January 1979, the start of the satellite record, to April 2014. I have not shown individual months, as monthly variations can be quite large, and would simply serve to muddy the waters. Instead, I have shown the 12-Month average of the differences.
There are some marked ups and downs in the record up to about 1995. This may be due to early inaccuracies in the satellite dataset, though this would be pure speculation on my part.
Since then, though, certain patterns emerge:
1) During the major El Ninos of 1998 and 2010, RSS temperatures spike to higher levels than GISS. In other words, GISS minus RSS goes negative.
2) There was a period of a few years after 1998, when the two datasets ran closely together.
3) From around 2004, though, there has been a distinct and growing divergence, with GISS showing relatively more warming.
4) Over the full period, as the graph shows, there is a trend is towards greater warming on GISS.
It is also worth noting that the April 2014 temperature anomalies, based on the same 1979-1998 baseline, are as follows:
| GISS | RSS |
| 0.45C | 0.25C |
In other words, GISS are currently showing 0.20C more warming than RSS. This is a significant number, being nearly half of the observed warming, as measured against the 1979-98 average.
The purpose of this post is not to point the finger, and say that one or the other dataset is wrong. Nevertheless, I believe that the differences observed raise serious questions about the accuracy of our global temperature measurements.
See the original Dohbro post
Sources
1) GISS –
http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt
2) RSS
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What ever happened to UAH? I thought it was the satellite record of choice for folks here, given that Christy and Spencer created it?
What Zeke said. UAH follows the surface measures. It is RSS that diverges.
Here is what Roy Spencer said:
“Anyway, my UAH cohort and boss John Christy, who does the detailed matching between satellites, is pretty convinced that the RSS data is undergoing spurious cooling because RSS is still using the old NOAA-15 satellite which has a decaying orbit, to which they are then applying a diurnal cycle drift correction based upon a climate model, which does not quite match reality.”
Paul – thanks for the post! Great analyses.
You wrote [Quote] “The purpose of this post is not to point the finger, and say that one or the other dataset is wrong. Nevertheless, I believe that the differences observed raise serious questions about the accuracy of our global temperature measurements.” [unQuote].
That is EXACTLY what I tried to accomplish with my analyses as well. I am not finger pointing, just raising questions. As I wrote in my essay “One can write a long essay about all the important difference between how each calculates the monthly GSTA, and for sure that is important, [this of course refers to the different base-line temperatures!] but here I simply and only want to compare each data set and see how well (or bad) they match each other. E.g. is one data set consistently reporting higher or lower than the others, are these differences increasing or decreasing over time or not? Etc. I am not assigning any subjective value to these possible differences; I just want to see if there are any differences and if there is a trend in these differences.” That was all, and is all.
Follow up posts like yours were my intent so we start to think about these different data sets and what they report and how the data discrepancies may differ (more) over time. However, and in addition, your work using similar base-lines finds the same pattern as my work: increasing difference over time in reported GSTA between (a) land-based and (a) satellite-based data set. That’s all there is to it, and that’s all we need to know, and warrants attention.
I’m really glad to see a discussion of temperature measurement errors. We should all remember that each temperature measurement, satellite or ground, has some error. To measure air temperature to 0.2 degrees C takes a very good and very expensive thermometer and enclosure and a very good location. If one has a large number of good thermometers and averages them, the accuracy improves somewhat, but never to perfection. And, lets face it, this whole debate is over temperature anomalies that are larger than the error of any thermometer made prior to 1900. I own a $400 Omega platinum resistance thermometer and I have routinely measured a 0.5 degree F (0.28 deg. C) temperature difference (in the shade, in a louvered container) between my front yard and back yard with it. The error, day or night, is never less than 0.1 deg. C. So even with the best equipment, short distances matter. I wonder if this whole debate is useless because of the small differences we are arguing about. The Younger Dryas warming dwarfs all of this.
The graph at Nick’s Moyhu site also shows that RSS is an outlier–if Paul were to compare UAH (or any other other ground-based systems) to RSS he would see something similar to the GISS-RSS comparison.
http://www.moyhu.blogspot.com.au/p/latest-ice-and-temperature-data.html#Px1
When UAH data is presented, it’s decried as being produced by “skeptics” and “you should be using RSS instead.”
As Spencer’s page says…”So, why the discrepancy? Well, if it was OUR (UAH) data that was cooling relative to RSS, people would accuse us of being bought off by Exxon-Mobil (I wish!…still waiting for that check..). At least that has been the history of this debate.
But now WE are the ones with “excess” warming. So where are the accusations that RSS is being bought off by Big Oil?…”
Something I’ve noticed over time (as a layman) is that the GISS plot, compared to the satellite series, seems to be adjusted to maintain an overall upward trend possibly to accord with the monotonic increase in CO2:
http://woodfortrees.org/plot/gistemp/from:1979/mean:13/offset:-0.2/plot/rss/mean:13
Paul – just wanted to say that -not surprisingly- using the none-baseline-adjusting the difference between GISS and RSS follows the exact same pattern as what you described both for the monthly data as well as for the 12 month running average data (I can’t post a plot here, so please see: https://www.dropbox.com/s/4c9kovx9n8zsvsv/GISS%20vs%20RSS.pdf). You didn’t provide a trendline (slope). So could you please be so kind to let us know what the the trendline, slope, for the baseline-adjusted data is, so we can compare that with the none-adjusted data.
Nonetheless, adjusting the data doesn’t change the fact that the data-bases are increasingly diverging over time, which is what’s important.
thanks!
david
I dunno Nick, seems like UAH has historically been diverging from GISS as well, at least until recent years.
Better define “follows the surface measures.”
david dohbro,
As one of the folks who raised some criticisms of your essay, I would like to extend thanks to you for bringing up the idea of the analysis. I do wish you had been given the opportunity to better complete your own analysis. Perhaps you and Paul can collaborate on future posts to analyze more the differences between the datasets.
Jimmy – thanks for the critiques and thanks for your kind words here. Collaboration is always good and I am always open to it. Especially since I have a few other data-analyses on going which are much more data-intense and much more extensive, complicate and I can therefore use all the help I can get!
Technically, this is the opposite of what the theory predicts.
The lower troposphere is supposed to warm by 1.3 to 1.4 times as fast as the surface. Instead, it is more like 0.5.
So, that either indicates surface data tampering or the theory is incorrect. Take your pick Nick and Zeke.
Obviously, you don’t care what the data shows. Repeat after me three time. Global warming is real, and it is caused by humans, Global warming is real …
II’m totally confused. If you choose the UAH and RSS trends from 1979 (over a third of a century) at WFTs UAH is lower than RSS. What am I missing and please don’t put the boot in too hard. As usual I can’t supply a link at WUWT.
@Nick Stokes & @Zeke Hausfather
As per the link you provided here is the full quote –
“If we look at the entire 30+ year record, we see that the UAH and RSS temperature variations look very similar, with a correlation coefficient of 0.963 and linear trends which are both about +0.14 deg. C per decade.”
In other words there is no difference between RSS and UAH over the period of the analysis because RSS is a bit warmer in the past and a bit cooler in the present.
I appreciate skepticism. I even appreciate skepticism of skepticism. But I see little point in being skeptical if the result is to mislead. It is hard to believe this was merely due to ignorance when your claim is refuted in the very link you provided.
Bill Illis says:”…that either indicates surface data tampering or the theory is incorrect.”
Bingo! Game, set and match!
Settled Science Update At GISS
“In 1997, GISS showed a strong warming trend in the Southern Hemisphere from 1880 to 1910. Now they show a strong cooling trend during that same period. All to a precision of 0.01 degrees.”
http://stevengoddard.wordpress.com/2014/03/27/settled-science-update-at-giss/
Bill Illis says:
May 19, 2014 at 4:34 pm
According the GHG hypothesis, the atmosphere should warm earlier & more than the surface. In reality, just the opposite has been observed. But since the surface “data” have been so stepped on, bent, folded, spindled & mutilated, who knows?
CACA busted, again.
“But I see little point in being skeptical if the result is to mislead. “
I took it from David Dohbro’s post:
1979-2014
RSS-UAH y=-0.0034x+.. is -0.34°C/century
GISS-UAU = 0.0018x+.. or 0.18°C/century
And the quote I gave is correct.
In other words Nick, UAH diverges from GISS, just not as badly as RSS. Yippee.
Bill illis
Unfortunately its not that simple. This [is] well trammelled ground. No clear answers.
See discussions at climateaudit and climatedialog.
An inquiry. You indicate you have used a 12-month running average. Is this correct? This is a lagging indicating with respect to the time. Is that what you want to show? This is commonly used in stock analysis.
I have used for many years this same arguement that GISS was diverting at an ever increasing rate when I spotted it on the Junkscience.com data site:
Comparing UAH and RSS we find them closely matched: http://junksciencearchive.com/MSU_Temps/MSUvsRSS.html
Yet when we compare UAH to GISS there is an ever increasing divergence by GISS towards the positive: http://junksciencearchive.com/MSU_Temps/MSUvsGISTEMP.html
GISS under the direction of Hansen were [caught] out repeatedly “readjusting” their data so that older temps were lowered and newer temps were raised so that the line had a definite rise from left to right as it was viewed:
http://jonova.s3.amazonaws.com/graphs/giss/hansen-giss-1940-1980.gif
When it comes to temp data sets run by activists that want all industrialisation shut down like Hansen does, I get very wary and look for more unbiased sources.
I’ll just add what should be an obvious point here…divergence should be minimal considering the fact that temperatures have been flat for about half of the 1979-2014 period.
“””””…..Andy May says:
May 19, 2014 at 3:39 pm
I’m really glad to see a discussion of temperature measurement errors. We should all remember that each temperature measurement, satellite or ground, has some error……”””””
Andy, as I’m sure you know, there are some quite exquisite thermometers, capable of very precise temperature measurements. One of them is the HP quartz crystal thermometer, that can easdily resolve a thousandth of a degree C. Semiconductor (silicon) junction thermometers, can also resolve small increments.
A more important question for the silicon thermometers, is the absolute calibration accuracy; an area, where your PRT has a good reputation.
But in the end the MOST important consideration is ; just WHAT is it, that has the temperature being displayed on the readout. Is it the thermometer itself, or is it some other physical entity, whose Temperature you want to know.
This question is of paramount importance, when that “temperature” reading is something you are trying to control via some feedback loop. Offsets between the system, and the sensor, are a common source of process control errors.
@ur momisugly Steve Mosher
Yes, Gavin and the Big Red Dog at CA circa 2008. The theory really isn’t that complicated if you’ve been following the tripe for the last 25-30 years.
http://climateaudit.org/2008/12/28/gavin-and-the-big-red-dog/#comment-170492
Steve McIntyre says:
#24. Santer (Schmidt) et al begins:
Tropospheric warming is a robust feature of climate model simulations driven by historical increases in greenhouse gases (1–3). Maximum warming is predicted to occur in the middle and upper tropical troposphere.
That sure sounds like Clifford the Big Red Dog. Maybe they’ve “moved on”.