There is a new paper out that investigates something that has not previously been well dealt with related to the surface temperature record (at least as far as the author knows). “Sensor measurement uncertainty”. The author has defined a lower limit to the uncertainty in the instrumental surface temperature record.
UNCERTAINTY IN THE GLOBAL AVERAGE SURFACE AIR TEMPERATURE INDEX: A REPRESENTATIVE LOWER LIMIT
Patrick Frank, Palo Alto, CA 94301-2436, USA, Energy and Environment, Volume 21, Number 8 / December 2010 DOI: 10.1260/0958-305X.21.8.969
Abstract
Sensor measurement uncertainty has never been fully considered in prior appraisals of global average surface air temperature. The estimated average ±0.2 C station error has been incorrectly assessed as random, and the systematic error from uncontrolled variables has been invariably neglected. The systematic errors in measurements from three ideally sited and maintained temperature sensors are calculated herein. Combined with the ±0.2 C average station error, a representative lower-limit uncertainty of ±0.46 C was found for any global annual surface air temperature anomaly. This ±0.46 C reveals that the global surface air temperature anomaly trend from 1880 through 2000 is statistically indistinguishable from 0 C, and represents a lower limit of calibration uncertainty for climate models and for any prospective physically justifiable proxy reconstruction of paleo-temperature. The rate and magnitude of 20th century warming are thus unknowable, and suggestions of an unprecedented trend in 20th century global air temperature are unsustainable.
INTRODUCTION
The rate and magnitude of climate warming over the last century are of intense and
continuing international concern and research [1, 2]. Published assessments of the
sources of uncertainty in the global surface air temperature record have focused on
station moves, spatial inhomogeneity of surface stations, instrumental changes, and
land-use changes including urban growth.
However, reviews of surface station data quality and time series adjustments, used
to support an estimated uncertainty of about ±0.2 C in a centennial global average
surface air temperature anomaly of about +0.7 C, have not properly addressed
measurement noise and have never addressed the uncontrolled environmental
variables that impact sensor field resolution [3-11]. Field resolution refers to the ability
of a sensor to discriminate among similar temperatures, given environmental exposure
and the various sources of instrumental error.
In their recent estimate of global average surface air temperature and its uncertainties,
Brohan, et al. [11], hereinafter B06, evaluated measurement noise as discountable,
writing, “The random error in a single thermometer reading is about 0.2 C (1σ) [Folland,et al., 2001] ([12]); the monthly average will be based on at least two readings a day throughout the month, giving 60 or more values contributing to the mean. So the error
in the monthly average will be at most 0.2 /sqrt60= 0.03 C and this will be uncorrelated with the value for any other station or the value for any other month.
Paragraph [29] of B06 rationalizes this statistical approach by describing monthly surface station temperature records as consisting of a constant mean plus weather noise, thus, “The station temperature in each month during the normal period can be considered as the sum of two components: a constant station normal value (C) and a random weather value (w, with standard deviation σi).” This description plus the use of a 1 / sqrt60 reduction in measurement noise together indicate a signal averaging statistical approach to monthly temperature.
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I and the volunteers get some mention:
The quality of individual surface stations is perhaps best surveyed in the US by way of the commendably excellent independent evaluations carried out by Anthony Watts and his corps of volunteers, publicly archived at http://www.surfacestations.org/ and approaching in extent the entire USHCN surface station network. As of this writing, 69% of the USHCN stations were reported to merit a site rating of poor, and a further 20% only fair [26]. These and more limited published surveys of station deficits [24, 27-30] have indicated far from ideal conditions governing surface station measurements in the US. In Europe, a recent wide-area analysis of station series quality under the European Climate Assessment [31], did not cite any survey of individual sensor variance stationarity, and observed that, “it cannot yet be guaranteed that every temperature and precipitation series in the December 2001 version will be sufficiently homogeneous in terms of daily mean and variance for every application.”
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Thus, there apparently has never been a survey of temperature sensor noise variance or stationarity for the stations entering measurements into a global instrumental average, and stations that have been independently surveyed have exhibited predominantly poor site quality. Finally, Lin and Hubbard have shown [35] that variable field conditions impose non-linear systematic effects on the response of sensor electronics, suggestive of likely non-stationary noise variances within the temperature time series of individual surface stations.
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The ±0.46 C lower limit of uncertainty shows that between 1880 and 2000, the
trend in averaged global surface air temperature anomalies is statistically
indistinguishable from 0 C at the 1σ level. One cannot, therefore, avoid the conclusion
that it is presently impossible to quantify the warming trend in global climate since
1880.
The journal paper is available from Multi-Science publishing here
I ask anyone who values this work and wants to know more, to support this publisher by purchasing a copy of the article at the link above.
Congratulations to Mr. Frank for his hard work and successful publication. I know his work will most certainly be cited.
Jeff Id at the Air Vent has a technical discussion going on about this as well, and it is worth a visit.
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Part III of my reply.
Part I is here.
Part II is here.
This will be mercifully short, and will only focus on points EFS_Junior neglected in his follow-up.
In his first criticism, here, EFS_Junior wrote that separating error into its independent terms is “bogus, unnecessary, and without merit.”
In Part I, I described three authoritative sources doing exactly that, namely separating instrumental error into independent terms in order to assess their properties and contributions to total error. One of those sources was the surface temperature article by Brohan, et al. (2006), the paper I criticized in my E&E article.
In his replies to my post, EFS_Junior was silent on this point. He did not acknowledge these sources or withdraw his opinion.
EFS_Junior remained silent on his mistaken claim that the instrumental uncertainty sigma does not propagate through temperature time series.
EFS_Junior remained silent on his mistaken claim that my paper did not discuss bias offset errors.
EFS_Junior remained silent on his mistaken claim that my published analysis assumed all errors are stationary (“symmetric about a zero mean”).
He also remained silent on the obvious fact that his own analysis assumed all instrumental error is stationary and therefore averages away.
In his reply, EFS_Junior mistakenly interpreted the invisibility of systematic error to a test for random error, to mean that systematic error averages away.
This not only shows unfamiliarity with systematic error, but a general unfamiliarity with experimental error. Very little of experimental error is random. Non-random error always propagates and rarely autocancels.
EFS_Junior has remained silent on this central point.
EFS_Junior was also very pejorative of E&E, which reviewed and published a paper that he obviously had trouble understanding even after two readings and my explanation. His dismissive attitude toward E&E is therefore unjustified and so far unapologetic.
More on this point: from the Climategate emails, we know that scientists central to AGW have used reviewer privilege and pressured editors (who apparently often complied) to suppress contradictory science. Climate journals have thereby become systematically hostile to manuscripts with results contrary to AGW. This has forced some researchers to publish in alternative journals. The AGW-central scientists then exploit the use of alternative journals to politically discredit the contradictory papers and their authors; suggesting that if the science was truly sound it would be published in a climate journal (as theirs is). We know that, in science, arguments stand or fall by their internal merit, not by the paper they’re written on. So the tactic of the AGW scientists, of specious disparagement, is strictly an abuse of science.
EFS_Junior’s aspersive attitude toward E&E, while surely an honest opinion, seems likely in part due to the dishonest politics of collegial disparagement prevalent in AGW circles.
At the end, the points EFS_Junior failed to address are exactly those that play into the realization that surface air temperatures, especially 20th century surface air temperatures, are systematically inaccurate. Of course, how inaccurate they are will almost certainly remain unknowable because no one ever bothered to independently monitor the uncontrolled environmental variables.
And that lack points up the further truth that 20th century air temperatures were always for no-need-to-be-very-precise local weather use. Never for precision climate studies.
And in that we see that the temperature record has been systematically abused.
Yet one more unappreciated systematic error.