Monday 30 September 2013

Reviews of the IPCC review

The first IPCC report (Working Group One), "Climate Change 2013, the physical science basis", has just been released.

One way to judge the reliability of a source, is to see what it states about a topic you are knowledgeable about. I work on homogenization of station climate data and was thus interested in the question how well the IPCC report presents the scientific state-of-the-art on the uncertainties in trend estimates due to historical changes in climate monitoring practices.

Furthermore, I have asked some colleague climate science bloggers to review the IPCC report on their areas of expertise. You find these reviews of the IPCC review report at the end of the post as they come in. I have found most of these colleagues via the beautiful list with climate science bloggers of Doug McNeall.

Large-Scale Records and their Uncertainties

The IPCC report is nicely structured. The part that deals with the quality of the land surface temperature observations is in Chapter 2 Observations: Atmosphere and Surface, Section 2.4 Changes in Temperature, Subsection 2.4.1 Land-Surface Air Temperature, Subsubsection Large-Scale Records and their Uncertainties.

The relevant paragraph reads (my paragraph breaks for easier reading):
Particular controversy since AR4 [the last fourth IPCC report, vv] has surrounded the LSAT [land surface air temperature, vv] record over the United States, focussed upon siting quality of stations in the US Historical Climatology Network (USHCN) and implications for long-term trends. Most sites exhibit poor current siting as assessed against official WMO [World Meteorological Organisation, vv] siting guidance, and may be expected to suffer potentially large siting-induced absolute biases (Fall et al., 2011).

However, overall biases for the network since the 1980s are likely dominated by instrument type (since replacement of Stevenson screens with maximum minimum temperature systems (MMTS) in the 1980s at the majority of sites), rather than siting biases (Menne et al., 2010; Williams et al., 2012).

A new automated homogeneity assessment approach (also used in GHCNv3, Menne and Williams, 2009) was developed that has been shown to perform as well or better than other contemporary approaches (Venema et al., 2012). This homogenization procedure likely removes much of the bias related to the network-wide changes in the 1980s (Menne et al., 2010; Fall et al., 2011; Williams et al., 2012).

Williams et al. (2012) produced an ensemble of dataset realisations using perturbed settings of this procedure and concluded through assessment against plausible test cases that there existed a propensity to under-estimate adjustments. This propensity is critically dependent upon the (unknown) nature of the inhomogeneities in the raw data records.

Their homogenization increases both minimum temperature and maximum temperature centennial-timescale United States average LSAT trends. Since 1979 these adjusted data agree with a range of reanalysis products whereas the raw records do not (Fall et al., 2010; Vose et al., 2012a).

I would argue that this is a fair summary of the state of the scientific literature. That naturally does not mean that all statements are true, just that it fits to the current scientific understanding of the quality of the temperature observations over land. People claiming that there are large trend biases in the temperature observations, will need to explain what is wrong with Venema et al. (an article of mine from 2012) and especially Williams et al. (2012). Williams et al. (2012) provides strong evidence that if there is a bias in the raw observational data, homogenization can improve the trend estimate, but it will normally not remove the bias fully.

Personally, I would be very surprised if someone would find substantial trend biases in the homogenized US American temperature observations. Due to the high station density, this dataset can be investigated and homogenized very well.

Friday 27 September 2013

AVAAZ petition to Murdoch to report the truth about climate change

AVAAZ is a digital civil rights organisation, whose petitions and actions have influenced many important political decisions in the last few years.

Because, the summary for policy makers of the new IPCC report is published today, they are now organising a petition asking Rupert Murdoch to report the truth about climate change. The petition just started; they already have half a million signatures after one day.

To Rupert Murdoch:

The scientific consensus that human activities are causing dangerous climate is overwhelming, yet your media outlets around the world continue to seed doubt and spread inaccuracy. Any journalism that does not first acknowledge the evidence that humans are causing this problem is dangerous and irresponsible. As concerned citizens we call on you to tell the truth about man made climate change and report on what we must do to solve this problem.

You can sign this petition here. Please spread the word.

Tuesday 10 September 2013

NoFollow: Do not give WUWT & Co. unintentional link love

The hubris at WUWT.
Do you remember the search engine AltaVista? One reason it was overrun by Google, was that Google presented the most popular homepages at the top. It did so by analysing who links to who. Homepages that receive many links are assumed to be more popular and get a better PageRank, especially when the links come from homepages with a high PageRank.

The idea behind this is that a link is a recommendation. However, this is not always the case. When I link to WUWT, it is just so that people can easily check that what I claim WUWT has written is really actually there. It is definitely not a recommendation to read that high-quality science blog. To the readers this will be clear, but Google's algorithm does not understand the text, it cannot distinguish popularity from notoriety.

This creates a moral dilemma. Do you link to a source of bad information or not? To resolve this dilemma, and make linking to notorious pages less problematic, Google has introduce a new HTML-tag:

<a href="" rel="nofollow">Some homepage</a>.

If you add NoFollow to a link, Google will not follow the link and not interpret the link as a recommendation in its PageRank computation.

Skeptical sunlight

We are not the only ones with this problem. Many scientifically minded people have this problem, especially people from skeptical societies. Note, that here the word skeptical is used in the original meaning. From them I have this beautiful quote:
As Louis Brandeis famously said, "sunlight is the best disinfectant". Linking directly to misinformation on the web and explaining why it is wrong is like skeptical sunlight. ...

I think the correct way to proceed is to continue providing skeptical sunlight through direct linking. For one thing this demonstrates that we are not afraid of those who we oppose. In general they don’t link back to us, and that demonstrates something to casual readers who take note of it. ...

But while we are doing this we must be constantly vigilant of the page rank issue. Page ranking in Google is vitally important to those who are pushing misinformation on the web. It is how they attract new customers to their vile schemes, whether they be psychics or astrologers or homeopaths or something else. Even if we as skeptics are providing only a miniscule fraction of a misinformation peddler’s page rank, that fraction is too much.
Our links are probably the smallest part, but they may be important nonetheless. These links connect the climate ostrich pages with the main stream. Without our links, their network may look a lot more isolated. This is also important, PageRank is not just about links, but about links from authoritative sources.

If you search in Google using:

You will find many pages linking to WUWT that most likely do not want to promote the disinformation, on the contrary.

Wednesday 4 September 2013

Proceedings of the Seventh Seminar for Homogenization and Quality Control in Climatological Databases published

The Proceedings of the Seventh Seminar for Homogenization and Quality Control in Climatological Databases jointly organized with the Meeting of Cost ES0601 (Home) Action MC Meeting (Budapest, Hungary, 24-27 October 2011) has now been published. These proceedings were edited by Mónika Lakatos, Tamás Szentimrey and Enikő Vincze.

It is published as a WMO report in the series on World Climate Data and Monitoring Programme. (Some figures may not be displayed right in your browser, I could see them well using Acrobat Reader as stand-alone application and they did print right.)