Saturday, 15 December 2012

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.

The NVAP dataset

The NASA Water Vapor Project dataset is made to study climate, but not to study trends, its strength is being able to study spatial patterns in humidity. To cite from the paper:

"Changes to input datasets and selected algorithms were made with each phase of processing, incorporating improved data and processing methodologies, but resulting in several time-dependent artifacts that degraded the dataset’s decadal uniformity. These changes, in combination with the dataset’s relatively short period of record, make the heritage NVAP dataset unsuitable for long-term trend analysis [Trenberth et al., 2005]."

The heritage NVAP dataset is the previous version with data from 1988 to 2001 (thank you RomanM for noting that this should be explicitly stated). This dataset has strong jumps (inhomogeneities), which you can even see by eye; see Figure 1 of the article. For the new dataset, they have put effort into reducing these artifacts. This is explained in the Auxilary Material, especially in Text S1; it looks like this material is not behind a pay wall. Still they only claim:

"NVAP-M Climate is designed for studies on seasonal to interannual timescales on various spatial scales."

There is no claim of usefulness to study trends. From a previous dataset you can see the beautiful global spatial patterns that can be observed by satellites. If you click on the image you go to a page where you can see a beautiful animation of the pattern for an entire year.


Further mistakes

Furthermore the post claims that "Climate modelers assume that water vapor, the principle greenhouse gas, will increase with carbon dioxide". This is wrong or at least misleading: humidity is expected to follow the temperature, in as much as temperature follows carbon dioxide, humidity will indirectly follow carbon dioxide.

In one of the comments of Mims, he complains about the line: "Thus water vapour at the surface and through the troposphere has very likely been increasing since the 1970s." in the Second Order Draft of the upcoming IPCC report. And he claims: "This conclusion is contradicted by the 2012 NVAP-M paper discussed in the rows immediately above." However, the NVAP-M dataset started in 1988 and there is thus no contradiction.

Open access publishing

Water vapor is an interesting variable. It is a strong greenhouse gas and an integral part of the hydrological cycle. Getting the spatial pattern of humidity and its temporal variability is thus very important. Consequently, it is important that we understand the quality of available measurement datasets well and that climate models reproduce the humidity measurements accurately. Unfortunately, the WUWT post was no contribution to such a scientific debate, it was just a lot of misinformation. Once again.

I wish all scientific articles were open to the public. That would make this type of misinformation by climate "skeptics" more difficult.

Fortunately, more and more people seem to realize the quality of WUWT and the reach of this blog, as measured by Alexa is going down.


Further reading

Water Vapor Trends
The Science of Doom has two long posts about trends humidity in radiosonde, satellite and reanalysis data. The posts are long because parts provide much background information for a lay audience.

More posts on homogenisation

Homogenisation of monthly and annual data from surface stations
A short description of the causes of inhomogeneities in climate data (non-climatic variability) and how to remove it using the relative homogenisation approach.
New article: Benchmarking homogenisation algorithms for monthly data
Raw climate records contain changes due to non-climatic factors, such as relocations of stations or changes in instrumentation. This post introduces an article that tested how well such non-climatic factors can be removed.
HUME: Homogenisation, Uncertainty Measures and Extreme weather
Proposal for future research in homogenisation of climate network data.
A short introduction to the time of observation bias and its correction
The time of observation bias is an important cause of inhomogeneities in temperature data.

More posts on WUWT

The age of Climategate is almost over
Shows that the number of readers of WUWT and climate audit is going down and that the number of comments at WUWT is down by 100 comments a day.
Blog review of the Watts et al. (2012) manuscript on surface temperature trends
A fast preliminary review of an unpublished erroneous manuscript by Anthony Watts and colleagues.
Investigation of methods for hydroclimatic data homogenization
An example of the daily misinformation spread by the blog Watts Up With That? In this case about homogenization.

Reference

Vonder Haar, T. H., J. L. Bytheway, and J. M. Forsythe (2012), Weather and climate analyses using improved global water vapor observations, Geophys. Res. Lett., 39, L15802, doi: 10.1029/2012GL052094.

8 comments:

thefordprefect said...

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-86-2-245

Worth a visit - download the free paper and check out figure 8

2 moth lag between temperature and water vapour - ish

This from the abstract TPW=total precipitable water:
...Further, we found out that the TPW anomalies are driven by the global surface temperature anomalies, but with a lag.

William Connolley said...

Thanks for that. I'd wondered what was wrong with Mims's analysis, but not hard enough to find out for myself.

Anonymous said...

In a discussion of the increase in water vapor in the atmosphere on a popular debate forum, one of the denier cultists posted the stuff from Mims via WUWT so I checked him out. If you check his Wikipedia entry, you'll find that he graduated from Texas A&M University in 1966 with a major in government and minors in English and history, he has no formal academic training in science, he is an advocate for Intelligent Design, and he is an avowed skeptic of global warming. One thing in the Wiki entry that sort of summed up where this guy is at for me was this: "In May 1988 Mims wrote to Scientific American proposing that he take over The Amateur Scientist column, which needed a new editor. Despite concern about his views, he was asked to write some sample columns, which he did in 1990. Mims was not offered the position, due, Mims alleges, to his Christian and creationist views."

Victor Venema said...

Link to that Wikipedia article. I had not expected that being a creationist would be a problem for the Scientific American. That would exclude almost half of the American population?

Anthony Watts does not seem to fear colorful guests. There was recently a WUWT guest post by Henry H. Bauer (>Wikipedia), who believes in the monster of Loch Ness, does not believe that HIV causes AIDS, etc.

And is it just me, or are the comments at WUWT getting worse? Some are outright insane and naturally claim that their theories are not accepted because scientists do not understand high-school physics. Sounds like the decline in number of readers the last year is mainly because of normal people leaving and the radicals are left behind.

PeeBee said...

I tried to post a comment on WUWT, stating it should be permissible to call someone a denier if they didn't agree with generally accepted scientific fact such as the sun being the centre of the universe or the earth was a globe or the earth has increased in temperature in the last 150 years or the concentration of CO2 concentration in the atmosphere was increasing. Needless to say it didn't get past the moderators! No wonder you are left with mutters posting when you have such a strict moderation policy.

Victor Venema said...

I guess they have the house right, but it is another blow to their credibility that they complain that other do what they do so unfairly.

In the discussion below the Mims guest post, people like Mario Lento can make trolling comments such as: "People are suffering and many deaths can be blamed on policies created as a result of the IPCC. Would you like proof of that? Do you feel any amount of shame for helping promote death?"

This comment would have been deleted for trolling if I had made it about them. Pure hypocrisy.

The opposition to the term climate denier is of a similar hypocritical vein. They simply do not like it because it indicates that they are the fringe group and then start to claim that it sounds holocaust denier. At least I had never made the connection before I heard it from them.

The main problem I see with the word "denier" is that it is too easy to circumvent. Such as this funny guy: "Climate change has happened, though I’m not sure how much after how much the actual station data is tortured to get a rising trend, but the question is how much is from CO2, which I believe is maybe 0.2 degrees."

0.2 is practically denying, but officially not, even if technically such a trend would probably not be significant. I like the term "climate ostrich" nowadays. That includes this fuzziness and has no connection with WWII.

Still, try to keep commenting politely at WUWT once in a while. You will not convince the regulars, but there are much more readers and it is good when such readers can find arguments and links to better information.

Carrick said...

PeeBee: I tried to post a comment on WUWT, stating it should be permissible to call someone a denier

I'm not sure why you assume that, because you don't find a particular label offensive, that immediately nobody else should either. It's somebody else's blog paid for from their pocket, they get to pick what words they are offended by and which they are not. I agree with Victor that there is some value in posting tempered comments that don't make value judgements on other's beliefs. I don't see any value of complaining about censorship when you violate commenting rules for a blog though.

Shadeburst said...

A very interesting post showing that you can prove anything with a play on words.

'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less.'

'The question is,' said Alice, 'whether you can make words mean so many different things.'

'The question is,' said Humpty Dumpty, 'which is to be master — that's all.'