New article on the multiple breakpoint problem in homogenization

An interesting paper by Ralf Lindau and me on the multiple breakpoint problem has just appeared in a Special issue on homogenization of the open access Quarterly Journal of the Hungarian Meteorological Service "Időjárás".

Multiple break point problem

Long instrumental time series contain non-climatological changes, called inhomogeneities. For example because of relocations or due to changes in the instrumentation. To study real changes in the climate more accurately these inhomogeneities need to be detected and removed in a data processing step called homogenization; also called segmentation in statistics.

Statisticians have worked a lot on the detection of a single break point in data. However, unfortunately, long climate time series typically contain more than just one break point. There are two ad hoc methods to deal with this.

The most used method is the hierarchical one: to first detect the largest break and then to redo the detection on the two subsections, and so on until no more breaks are found or the segments become too short. A variant is the semi-hierachical method in which old detected breaks are retested and removed if no longer significant. For example, SNHT uses a semi-hierachical scheme and thus also the pairwise homogenization algorithm of NOAA, which uses SNHT for detection.

The second ad hoc method is to detect the breaks on a moving window. This window should be long enough for sensitivity, but should not be too long because that increases the chance of two breaks in the window. In the Special issue there is an article by José A. Guijarro on this method, which is used for his homogenization method CLIMATOL.

While these two ad hoc methods work reasonably, detecting all breaks simultaneously is more powerful. This can be performed as an exhaustive search of all possible combinations (used by the homogenization method MASH). With on average one break per 15 to 20 years, the number of breaks and thus combinations can get very large. Modern homogenization methods consequently use an optimization method called dynamic programming (used by the homogenization methods PRODIGE, ACMANT and HOMER).

All the mentioned homogenization methods have been compared with each other on a realistic benchmark dataset by the COST Action HOME. In the corresponding article (Venema et al., 2012) you can find references to all the mentioned methods. The results of this benchmarking showed that multiple breakpoint methods were clearly the best. However, this is not only because of the elegant solution to the multiple breakpoint problem, these methods also had other advantages.

Could we get more Earthquakes due to global warming and thermal expansion of the Earth's crust?

Thermal expansion can release quite some force as is seen in bridges and railroad tracks that are deformed due to hot weather. I am wondering whether thermal expansion of the Earth's crust due to global warming can similarly lead to seismic activity, especially at subduction zones where one crustal plate slides under another one.

I have searched the scientific literature, but was unable to find any articles on the topic, while it sounds quite straight forward to me. Did really no one have this idea before, or was it already debunked in 1960?

Dear journalists, This is not a press release; I do not like science by press release. While I am a scientist, I have no special expertise in geology. Please only write about this if the standards of your publisher are so low that you would also write about it if you next-door neighbour would have this idea. In other words, please wait until there is a scientific publication on this. Even better would be to wait until there are several papers, but I realise that that is illusory. Dear "skeptics", I did not write that your SUV is responsible for the seismic atomic genocide of the the Japanese population. This post is only written to bring the idea under the attention of the right scientists. At this stage, it is very likely that the idea is wrong and that nothing will happen. Dear colleagues, the reason to write this post is to attend someone with the skills to investigate it. It is thus highly appreciated if you could forward it to someone who may have the right skills. I guess two skills are needed: 1) modelling of the warming of the crust and 2) dynamical modelling of the crust expansion. If you have one of these skills, please contact me, maybe someone with the second skill also responded. If you have both skills or know someone, feel free to act as if it is your own idea. Ideas are cheap and this back-of-the-envelope computation was quickly made. The real innovative step is deciding which idea is worth spending a year of your time on to make it into science. It would be nice if after publication you could act as if a colleague attended you to this post and send me a copy of the article. I am curious.

Back-of-the-envelope computation

The length of the Equator is roughly 40x10⁶ metres. And my high-school tables book gives thermal expansion coefficients for various stone types between 4 and 12x10^-6 K^-1. So for a one degree temperature change one would expect that the Earth's crust would expand by 160 to 480 metre. (More accurately, one would use the size of a plate not the circumference of the Earth. On the other hand, the projected temperature change is larger than one degree.) For the sake of the argument, let's say that it is about 100m. One thing I do not know is whether the crust is sufficiently brittle/solid (like a railway track or bridge that deforms by heat) or whether there are air and liquid pockets and cracks which could absorb the expansion. Furthermore, maybe the additional pressure would mainly increase the width of the crust not its length or the crust would just crumple a little more.

A database with daily climate data for more reliable studies of changes in extreme weather

In summary:

• We want to build a global database of parallel measurements: observations of the same climatic parameter made independently at the same site
• This will help research in many fields
• Studies of how inhomogeneities affect the behaviour of daily data (variability and extreme weather)
• Improvement of daily homogenisation algorithms
• Improvement of robust daily climate data for analysis
• Please help us to develop such a dataset

Introduction

One way to study the influence of changes in measurement techniques is by making simultaneous measurements with historical and current instruments, procedures or screens. This picture shows three meteorological shelters next to each other in Murcia (Spain). The rightmost shelter is a replica of the Montsouri screen, in use in Spain and many European countries in the late 19th century and early 20th century. In the middle, Stevenson screen equipped with automatic sensors. Leftmost, Stevenson screen equipped with conventional meteorological instruments. Picture: Project SCREEN, Center for Climate Change, Universitat Rovira i Virgili, Spain.

We intend to build a database with parallel measurements to study non-climatic changes in the climate record. This is especially important for studies on weather extremes where the distribution of the daily data employed must not be affected by non-climatic changes.

There are many parallel measurements from numerous previous studies analysing the influence of different measurement set-ups on average quantities, especially average annual and monthly temperature. Increasingly, changes in the distribution of daily and sub-daily values are also being investigated (Auchmann and Bönnimann, 2012; Brandsma and Van der Meulen, 2008; Böhm et al., 2010; Brunet et al., 2010; Perry et al., 2006; Trewin, 2012; Van der Meulen and Brandsma, 2008). However, the number of such studies is still limited, while the number of questions that can and need to be answered are much larger for daily data.

Unfortunately, the current common practice is not to share parallel measurements and the analyses have thus been limited to smaller national or regional datasets, in most cases simply to a single station with multiple measurement set-ups. Consequently there is a pressing need for a large global database of parallel measurements on a daily or sub-daily scale.

Also datasets from pairs of nearby stations, while officially not parallel measurements, are interesting to study the influence of relocations. Especially, typical types of relocations, such as the relocation of weather stations from urban areas to airports, could be studied this way. In addition, the influence of urbanization can be studied on pairs of nearby stations.

The social dimension of health

Maybe I could even have title this post: the social dimension of life.

Many people seem to interpret "survival of the fittest" as relating to the fitness studio. While the fittest are simply those who survived. Whether you survive depends on lot on your tribe and only partially on your self, if you do not behave too stupidly.

Frank Forencich speaking at the Ancestral Health Symposium, 2012, explains this social part of health and a full life.


Frank Forencich is blogging at The Exuberant Animal and is a refreshing sound in the paleo world. His posts are thought provoking and well worth reading.

A real paper on the variability of the climate

I am searching for papers on the variability of climate and its natural variability and possible changes due to climate change. They are hard to find.

The New Climate Dice

This weekend I was reading a potential one: the controversial paper by James Hansen et al. (2012) popularly described as "The New Climate Dice". Its results suggest that variability is increasing. After an op-ed in the Washington Post, this article attracted much attention with multiple reviews on Open Mind (1, 2, 3), Sceptical Science and Real Climate. A Google search finds more than 60 thousand webpages, including rants by the climate ostriches.

While I was reading this paper the Berkeley Earth Surface Temperature group send out a newsletter announcing that they have also written two memos about Hansen et al.: one by Wickenburg and one by Hausfather. At the end of the Hausfather memo there is a personal communication by James Hansen that states that the paper did not intend to study variability. That is a pity, but at least saves me the time trying to understand the last figure.

Reinhard Böhm

That means that the best study I know on changes in variability is a beautiful paper by Reinhard Böhm (2012), who unfortunately recently passed away, an enormous loss. His paper is called "changes of regional climate variability in central Europe during the past 250 years". It analyses the high-quality HISTALP dataset. This dataset for the greater Alpine region contains many long time series; many of the earliest observations were performed in this region. Furthermore, this dataset has been very carefully homogenized.

Reinhard Böhm finds no change in variability, not for pressure, not for temperature and not for precipitation. His main conclusions are:

• The first result of the study is the clear evidence that there has been no increase of variability during the past 250 years in the region.
• We can show that also this recent anthropogenic normal period [1981-2010, red.] shows no widening of the PDF (probability density function) compared to preceding ones.
• It shows that interannual variability changes show a clear centennial oscillating structure for all three climatic elements [pressure, temperature and precipitation, red.] in the region.
• For the time of being we have no explanation for this empirical evidence.

Catastrophic Anthropogenic Climate Change is a Fraud

Have you ever been called a proponent of the theory Catastrophic Anthropogenic Climate Change (CACC) or Catastrophic Anthropogenic Global Warming (CAGW)? Typically just the abbreviation. No? Then you probably never commented at a climate "skeptic" blog and suggested that possibly some aspect of climate science might be sound, if only by accident.

Photo of a wild fire by Zach Dischner used under a creative commons CC BY 2.0 license.

My guess would be that the "proponents of CAGW" are supposed to be scientists and people that tend to believe climatologists over climate "skeptics". So what does the scientific literature say about catastrophic climate change? In the Web of Science, you can find one article for the term "Catastrophic Anthropogenic Climate Change". For comparison there are "approximately 75,755" articles on "Climate Change".

This article is "the evolution of an energy contrarian", an autobiographical essay by a gas company manager and researcher Henry R. Linden. It does not make the impression that it was reviewed.

Abstract: An analysis of the forces that have shaped energy and energy-related environmental policies is presented through the eyes of an active participant in their evolution over the past 53 years. ... Today, proponents of catastrophic anthropogenic climate change, again claiming scientific consensus, threaten to create even greater energy market distortions at large social and economic costs. The author traces his conversion to energy contrarian to the general failure of consensus and to his own misjudgments in these critical policy areas.

(my emphasis)

Furthermore, there is one article for the term "catastrophic anthropogenic global warming", while there are "approximately 17,866" articles on "global warming". This article is another single-author paper and written by Alan Carlin (Wikipedia | his blog) for the Special Issue on Advances in Environmental Economics with guest editor Alan Carlin(!). This journal publishes very fast: one article of the special issue was published in 1 month, while Carlin's article took the longest, but it was still published within 3 months.

Abstract: Economic analyses of environmental mitigation and other interdisciplinary public policy issues can be much more useful if they critically examine what other disciplines have to say, insist on using the most relevant observational data and the scientific method, and examine lower cost alternatives to the change proposed. ...
The economic benefits of reducing CO(2) emissions may be about two orders of magnitude less than those estimated by most economists because the climate sensitivity factor (CSF) is much lower than assumed by the United Nations because feedback is negative rather than positive and the effects of CO(2) emissions reductions on atmospheric CO(2) appear to be short rather than long lasting. ...
The risk of catastrophic anthropogenic global warming appears to be so low that it is not currently worth doing anything to try to control it, including geoengineering.

(my emphasis)

You got to love it when an economist from the RAND company knows better what the climate sensitivity is as climatologists ("United Nations"). The irony is that this paper, which is a peer-review catastrophe, explains at length why citing non-reviewed works is fine and the peer reviewed literature on the climate sensitivity needs to be ignored.

This "paper" should never have been published in the scientific literature. Fortunately, it is well hidden in a journal on public health were no climatologist or economist will find it. In this way, the peer-review system did do its filtering job.

No trend in global water vapor, another WUWT fail

Forrest M. Mims III Forrest Mims is an interesting character. To quote from the introduction to his Science article on amateur science: "Forrest M. Mims III is a writer, teacher, and amateur scientist. He received a Rolex Award for developing a miniature instrument that measures the ozone layer and has contributed projects to “The Amateur Scientist” column in Scientific American. His scientific publications have appeared in Nature and other scholarly journals."

Anthony Watts just published a guest post by Forrest M. Mims III with the title: "Another IPCC AR5 reviewer speaks out: no trend in global water vapor". I have no special expertise in this area, but I am privileged being able to read the article that is discussed. This is sufficient to see that the article and its post are two different worlds. Update: An earlier draft is available (thanks, michael sweet).

First, note that being a "expert reviewer" does not say much. There are over a thousand reviewers, even Anthony Watts himself is an IPCC "expert reviewer". On the other hand, Mims may be an amateur, but did do valued scientific work on UV measurements.

The trend in global water vapor

The post discusses a paper by Vonder Haar et al. (2012) on the NASA Water Vapor Project (NVAP) dataset. The main piece of information missing from the post is that this dataset is only 22 years long. Almost any climatological measurement will not have a statistically significant trend over such a short period, but the story is even weirder.

Just as in the misleading post on homogenization of climate data earlier this year, Anthony Watts again proofs to have a keen eye in finding the best misinformation.

Mims added a list with all the comments of his review. In this list, Watts found this comment:

This paper concludes,

“Therefore, at this time, we can neither prove nor disprove a robust trend in the global water vapor data.”

Non-specialist readers must be made aware of this finding and that it is at odds with some earlier papers.

The complete citation from the Geophysical Research Letters article is:

"The results of Figures 1 and 4 have not been subjected to detailed global or regional trend analyses, which will be a topic for a forthcoming paper. Such analyses must account for the changes in satellite sampling discussed in the auxiliary material. Therefore, at this time, we can neither prove nor disprove a robust trend in the global water vapor data."

In other words, they cannot say anything about the trend, because they have not even tried to compute it and estimate its uncertainty. Especially estimating the error in the trend will be very difficult as the dataset uses different satellites for different periods of the dataset, which invariably creates jumps in the dataset that should not be mistaken for true climate variability or trends.

The paper is thus not at odds with earlier papers. These earlier papers studied longer periods and probably datasets which were more homogenenous and consequently did find a statistically significant trend. There is thus no contradiction.

Changing the political dynamics of greenhouse gas reductions

Photo by Caveman Chuck Coker, Creative Commons by-nd licence

Another climate conference failed miserably. Maybe we need a completely different system, a system in which forerunners are rewarded and not punished.

A stable, predictable climate is a common good. Climate change is one of the most difficult tragedies of the commons. There are great benefits to using energy and the climate costs are spread almost perfectly to everyone. No single industry or country contributes much to the problem, but some industries and countries do benefit strongly and have a large incentive to halt the negotiations and to spread doubt. This makes greenhouse gas mitigation arguably the most difficult tragedy of the commons.

It is possible to solve such tragedies, the Montreal protocol to curb emissions of chlorofluorocarbons (CFC) to protect the ozone layer seems to work well. The ozone layer is now at its thinnest, but scientists expect that is will start to become thicker soon and return to almost normal levels in several decades. However, in case of the Montreal protocol only the producers of fridges, air conditionings and spray cans were affected. Greenhouse gasses are emitted by the energy, agricultural and building sectors. These are powerful parties and this makes a global treaty difficult. Maybe it is better to solve the tragedy of the commons by allowing countries and regions that want to reduce their CO₂ emissions to protect themselves against unfair competition.