Since we have been paying a lot of attention to the surface record given the recent revelations surrounding the adjustments to data and NOAA’s release of the State of the Climate Report claiming that the USA had the hottest year ever (but the globe did not) this paper seems like a good one to review.
How Natural is the Recent Centennial Warming? An Analysis of 2249 Surface Temperature Records
Horst-Joachim Lu¨decke, Rainer Link, and Friedrich-Karl Ewert
EIKE, European Institute for Climate and Energy, PO.Box 11011, 07722 Jena, GERMANY
Abstract. We evaluate to what extent the temperature rise in the past 100 years was a trend or a natural fluctuation and analyze 2249 world- wide monthly temperature records from GISS (NASA) with the 100-year period covering 1906-2005 and the two 50-year periods from 1906 to 1955 and 1956 to 2005. No global records are applied. The data document a strong urban heat island effect (UHI) and a warming with increasing station elevation.
For the period 1906-2005, we evaluate a global warm- ing of 0.58 0C as the mean for all records. This decreases to 0.41 0C if restricted to stations with a population of less than 1000 and below 800 meter above sea level. About a quarter of all the records for the 100-year period show a fall in temperatures. Our hypothesis for the analysis is – as generally in the papers concerned with long-term persistence of temper- ature records – that the observed temperature records are a combination of long-term correlated records with an additional trend, which is caused for instance by anthropogenic CO2, the UHI or other forcings. We apply the detrended fluctuation analysis (DFA) and evaluate Hurst exponents between 0.6 and 0.65 for the majority of stations, which is in excellent agreement with the literature and use a method only recently published, which is based on DFA, synthetic records and Monte Carlo simulation. As a result, the probabilities that the observed temperature series are natural have values roughly between 40% and 90%, depending on the stations characteristics and the periods considered. ’Natural’ means that we do not have within a defined confidence interval a definitely positive anthropogenic contribution and, therefore, only a marginal anthropogenic contribution can not be excluded.
Electronic version of an article published in International Journal of Modern Physics C, Vol. 22, No. 10, doi:10.1142/S0129183111016798
…
In this paper, we have used 2249 unadjusted monthly temperature records of 100 and 50 years in length and evaluated the temperature changes for the periods 1906-2005, 1906-1955, and 1956-2005. Our analysis was based exclusively on local records and applied DFA, Monte Carlo methods and synthetic records. The main results and conclusions are the following.
a) The mean of all stations shows 0.58 0C global warming from 1906 to 2005. If we consider only those stations with a population of under 1000 and below 800 meter above sea level this figure drops to 0.41 0C and would probably decrease even further if we were to take into account the warm biases caused by the worldwide reduction in rural stations during the 1990s, by changes to the screens and their environments, and by the appearance of automatic observing systems.
b) From 1906 to 2005, about a quarter of all records show falling temperatures.
This in itself is an indication that the observed temperature series are pre- dominantly natural fluctuations. ’Natural’ means that we do not have within a defined confidence interval a definitely positive anthropogenic contribution and, therefore, only a marginal anthropogenic contribution can not be ex- cluded. We evaluated – with a confidence interval of 95% – the probability that the observed global warming from 1906 to 2005 was a natural fluctuation as lying between 40% and 70%, depending on the station’s characteristics. For the period of 1906 to 1955 the probabilities are arranged between 80% and 90% and for 1956 to 2005 between 60% and 70%.
c) By separating stations into specific station groups, such as those with a defined minimum population, a strong UHI and elevation warming can be identified.
d) The vast majority of temperature stations are found on land and in the northern hemisphere, and have Hurst exponent of α ≈ 0.63 in such locations. However, two thirds of the Earth are covered with water, and the relatively few stations on islands or near oceans have higher Hurst exponent of α ≈ 0.7. Therefore, a real exponent for the entire Earth could be some- what higher than α ≈ 0.63. Records with higher exponents embody even higher probabilities for natural fluctuations.
Full PDF: http://www.eike-klima-energie.eu/uploads/media/How_natural.pdf
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I find the last sentence of the abstract too torturous for my taste:”‘Natural’ means that we
do not have within a defined confidence interval a definitely positive anthropogenic contribution and, therefore, only a marginal anthropogenic contribution can not be excluded.” What do they mean?
Leif Svalgaard says at 1:57 pm
Imo, anthropogenic contribution if any is marginal…
Leif Svalgaard says:
January 11, 2013 at 1:57 pm
I find the last sentence of the abstract too torturous for my taste:”‘Natural’ means that we
do not have within a defined confidence interval a definitely positive anthropogenic contribution and, therefore, only a marginal anthropogenic contribution can not be excluded.” What do they mean?
===============================================================================
Mr. Layman here. It does sound contradictory. Perhaps, “only a marginal anthropogenic contribution can be included.” ?
No reference to Watts el al in the 84 references.
Nature means we cannot detect the hand of mann?
Not sure if this is an honest evaluation or an introduction of a weasel clause.
Personally I prefer E.M. Smiths explanation, as he’s covered most of this in a language I can understand.
They can’t rule out some – small to minuscule to infinitesimal – AGW effect.
Well I guess the meaning may be obscure but the implication seems to be we anthropomorphs are not natural entities.
Leif has it right. Bafflegab with multiple negatives leaves the readers mystified.
A technical paper with practical conclusions.
I think they mean to say that a marginal anthropogenic contribution can not be excluded.
To me this means that an important anthropogenic contribution can be excluded.
For the period 1906-2005, we evaluate a global warm- ing of 0.58 0C as the mean for all records. This decreases to 0.41 0C if restricted to stations with a population of less than 1000 and below 800 meter above sea level.
————
Geeeee wizzz. They have discovered the urban heat island effect all by themselves.
And then simply waved their hands around busily and declared that all of the 0.4 degrees rise they found must be natural. With no evidence produced one way or the other. And ignoring the logic of the obvious: the trend “by itself” is not evidence of causation.
And just making stuff up by declaring “probably” with lots of speculation and no evidence.
And hope no one notices they ignore both the ocean temperature and satellite trends.
And no novelty to justify this as a scientific publication. This kind of analysis has been done to death already.
Leif–They give a rather simpler definition on p. 7:
‘Natural’ denotes that there is no defi nite anthropogenic trend in the record.
Then on p. 9 there is a long section explaining how they establish a confidence level roughly corresponding to a 95% range within which an external (anthropogenic) trend can be excluded. They appear to be of the same opinion as Leif and several commenters here since they express dissatisfaction with their own definition, calling it “correct but somewhat clumsy”
I think this is what the authors are saying is ’Natural’ means that we do not have within a defined confidence interval a definitely positive anthropogenic contribution but that said, a marginal anthropogenic contribution cannot be excluded. Or in other words temperature fluctuations in the period studied are probably mainly due to natural causes but with a small amount probably due to human actions
” ’Natural’ means that we do not have within a defined confidence interval a definitely positive anthropogenic contribution and, therefore, only a marginal anthropogenic contribution can not be excluded.”
….
I think that is the ‘Get Out of Peer Review Free Card’ They know darn well they can not come right out and say the study shows no sign of “a definitely positive anthropogenic contribution “ and get the paper published so they put in that bit of bafflegab to get it past the journal editor and reviewers.
Figure 6 provides an estimate of the strength of UHI compared to stations with populations less than 1000: about 0.3 C higher for Pop=10,000, 0.5 C (100,000), 0.8 C (1,000,000), >1 C for
>4,000,000.
Considering the 100-year increase was only 0.58 C, this appears to indicate that UHI was a substantial fraction of the increase (as our host suggests in his latest draft paper.)
The authors used the GISS unadjusted monthly data, so did not allow the grid-based homogenization to mess up their estimates.
I think the last paragraph of the abstract is a classic. Given the degree to which the doom-sayers are logic-challenged, it might head them off at the pass.
@Leif they mean English is not their first language
Leif – In all probably it’s either translated from German or it’s not in the writer’s first language. Maybe a bit of leeway should be granted on the exact wording.
General comment –
The study uses population as a station selection criterion. It would have been better to use the physical surroundings of the stations as in Watts 2012. Obviously that can’t be done (too many stations) if the information is not readily available.
The study’s stated probabilities in (b) look odd to me. I would expect the probability for any particular proposition (in this case that the observed global warming is a natural fluctuation) would be nearer to 50% (the “don’t know” value) for shorter study periods (because, if the study period is very short then you just can’t tell). Their probabilities go the other way. I *think* this may come from their use of linear trends, since counterintuitively the trends in the two halves of an interval can both be greater (or both less) than the trend of the whole (because the two half trends don’t have to meet in the middle). Or, it may come from the way the proposition is interpreted (“‘Natural’ denotes that there is no defi nite anthropogenic trend in the record.“). Either way, I *think* that means that their probabilities are incorrect. Unless some kind individual can explain it to me nice and simply, it looks like I’ll have to spend a lot more time on the paper in order to understand its findings.
That temperature trends for single stations are not statistically significant is no surprise. If you want to see changes in the global climate, you do so by computing and analyzing the global mean temperature. A local time series of a single station, or even an average over a signal nation, will show a much larger natural variability as the global mean temperature.
To make matters worse, the authors have used inhomogeneous data in which jumps (relocations, screen changes, instrument changes, etc.) and gradual trends (for example due to urbanization) are still present. This is a large part of the long term variability. The statement that the variability is natural is thus false, the variability is to a large part due to inhomogeneities.
Due to the inhomogeneities also the Hurst coefficient is overestimated and consequently the authors overestimate the uncertainty in the trends.
It is probably not a coincidence that the paper is published in a computational physics journal. Climate “skeptics” like such journals, as they are less likely to have reviewers that are knowledgeable. Which physicist knows that there are inhomogeneities in the climate record? I surely did not after studying physics. That is something I learned when I started working on climatological problems. Also a physicist is less likely to realize that it makes a difference whether you study a local station time series or a global average. Only a small fraction studies complex systems and this topic is typically not part of the physics curricula.
REPLY: Well, you are entitled to your speculation, doesn’t mean it is right- Anthony
I’ve been saving about 30 stations of temp data listed on GISS site for some time. Just in the last few months there have been unusually large changes to the past data. About a third of the stations have had the last several years of data vanish. My saved text files show that most of those had shown significant cooling in those last few years. Three stations, Beaver City, Honolulu and Norfolk Island have had early 20th century data replaced to show massively cooler temps, resulting in what now appears to be an obvious warming trend. Almost every station has had substantial changes in at least of few years of data. One station, Hilo, has “vanished”
A few stations seem to be resisting alteration, Vostok, Halley and Davis in Antarctica. The Amundsen-Scott data are usually stabel but now show small changes.
There are thousands of stations accessible from the GISS page, but if those stations are being changed in the same proportions as the my small sampling, then there are massive problems with the GISS data. I can’t imagine any valid scientific justification for what has recently been happeining. I hope others who are watching past surface station data maintain their old data files.
Sorry, boys and girls, for how long this comment is, but:
THIS is the paper I was looking for when I first became interested in global warming – as a neutral observer with no bone to pick. That was over a decade ago. I had never found it. Till now.
Thanks to Lüdecke, Link, and Ewert! FINALLY someone has done this study. Bravissimo!
And now that they have, what do they find?
1. Anthropogenic forcings are a minor player.
2. UHI is a considerable factor [duh] (…the real anthropogenic factor in global warming…)
3. The 1989 Dying of the Thermometers needs to be looked at and included
4. Global averages are a BAD way to do it, because, as the authors say:
Those two points – the attenuation and the standard deviation – about the Mannian global averaging I have ranted about more than once here, though not using the standard deviation specifically (though in my mind it is a natural fallout of the attenuation). In my mind, losing sight of the extremes is a sure sign that the methodology is WRONG.
Temporal Rectification of proxies to each other
I also think that the global proxies have extremes within each proxy that are lost when combining them and not trying to temporally rectify their extremes. I saw this on one spaghetti graph posted here about four years ago (the author I can’t recall), where extremes of the different proxies were time-shifted from each other. I made the point here (and I think also at CA) that the uncertainty factors apply to TIME as well as magnitude. Why? Because the time element in many proxies (if not all) is uncertain, and this makes extremes in one misalign with extremes of others. When homogenizing for combining, these extremes cannot but be minimized, when in reality all the extremes do show up in the individual proxy records, and if those extremes are flattened/attenuated by the combining method, then the method CANNOT be correct. Averaging in itself will attenuate. But without consciously attempting to keep the those extremes in the record, through to the final graph, the extremes will be flattened and perhaps lost altogether (which is what Mann’s Hockey Stick HANDLE is all about). The extremes are REAL in the data. If any method overly attenuates them, then that should be a red flag that a better method (probably more complex) needs to be applied. If that method doesn’t exist, then a careful development of such a method needs to be developed and vetted I.e., the homogenization cannot be left standing as the proper way to analyze and/or present the data. It is imperative to develop that better method; until that is done, everyone is farting in the wind.
I am just ecstatic that this study has finally been done. To me, THIS is the definitive paper, the one that can BEGIN the beginning of an assessment of our true climate history. It MAY even make it possible to have good climate models, once people get rid of the wrong assumptions and accept the strength of the natural variations. Just adding in correct individual UHI values for stations will be a great step forward (instead of adding a global UHI value out of sheer laziness).
Steve Garcia
The Graph of Temperature vs. Number of Stations
http://www.uoguelph.ca/~rmckitri/research/nvst.html
Says it all?
Feet2theFire- link to paper would be useful thanks.
Bravo. Simple thesis: Recent changes are unusual, but NOT global. Different areas are changing in DIFFERENT DIRECTIONS. Therefore you can’t possibly assume a global cause. You have to look for local or regional causes.
Remove the fogging double negative and the last sentence means that a definitely positive anthropogenic contribution can be excluded. Now I’ll go read comments and see if anyone agrees.
==========
Well, several and many agree. There is a metaphor with climate, foggy at times. It’s always been all about the albedo.
===========
AK, @ur momisugly 1:55 AM. Ungodly. Eyeballing, that’s nearly a two degree warp.
==================