The disclosure of climate data from the Climatic Research Unit at the University of East Anglia - Science and Technology Committee Contents

Memorandum submitted by Nicholas Barnes and David Jones (CRU 57)

  We are writing with regard to the evidence your committee has heard on the Climatic Research Unit (CRU) at the University of East Anglia. We are software experts with long industrial experience. We also have some expertise in climate science software such as that discussed in evidence, particularly the oral evidence from Professor Jones of CRU and Professor Slingo of the Met Office, and a number of evidence memoranda. We hope that our submission may clarify some of the issues raised by that evidence.

  Nicholas Barnes has been a professional software engineer since 1990; David Jones has been a professional software engineer since 1994. In 1997, Nicholas founded a software consultancy firm called Ravenbrook Limited, which he continues to run today. David has worked for Ravenbrook since 2003. We work in various industry sectors, including desktop data analysis, games development, memory management, software tool integration, and robotic control. We both have degrees in mathematics, and post-graduate diplomas in computer science, from the University of Cambridge. We both have life-long interests in science and in computers.

  In 2008 we started Clear Climate Code, a volunteer pro-bono project, because we saw that the clarity of software published by climate scientists was disrupting the public debate about climate change. You have asked questions and heard evidence about this disruption.

  The goals of the Clear Climate Code project are:

    1. To produce clear climate science software;

    2. To encourage the production of clear climate science software; and

    3. To increase public confidence in climate science results.

  We aim to increase public confidence in results by publishing and clarifying the software which produces those results. That process will certainly uncover and correct errors. These corrections are essential to the goal. We don't want the public to trust incorrect results; any incorrect results should be visibly corrected, so that the public may trust them.

  Several other people around the world have joined and helped us in our efforts. We publish all of our work at and make presentations about it at conferences.

  The main focus of Clear Climate Code so far has been on GISTEMP.

  GISTEMP is a gridded dataset of global historical surface temperature anomalies, substantially similar to the HadCRUT3 dataset produced jointly by the Met Office Hadley Centre and by CRU. GISTEMP produces a "Global Land-Ocean Temperature Index", a chart that shows how global temperatures have changed since 1880. see This chart is the analogue of HadCRUT3's "Global average temperature" chart, see

  The source code that produces the GISTEMP analysis is published, see All the data used in the GISTEMP analysis is also published. Clear Climate Code have been reimplementing this analysis, with an emphasis on clarity. The intention is that anyone interested in the subject, and capable of understanding a program, should be able to download our software and easily follow it. Collectively we have closely examined every part of the original GISTEMP source code and produced a new version that produces exactly the same results as GISTEMP. We continue to refine our version, to improve its clarity. Dr Reto Ruedy, a mathematician at NASA GISS with responsibility for GISTEMP, has said recently that they would like in future to use our version.

  As part of this process, we have read several of the scientific papers that describe the GISTEMP analysis, including:

    J Hansen, R Ruedy, J Glascoe, Mki Sato, J Geophys Res 104, 30997-31022, doi:10.1029/1999JD900835 (1999).

    J E Hansen, S Lebedeff, J Geophys Res 92, 13345-13372 (1987).

  It is obvious to us that the original GISTEMP software is not engineered to a high quality. But this is not at all unusual for scientific software, or for software in the commercial sector.

Scientists generally receive little or no training in software development. In making our new implementation we have found a few minor problems or "bugs" in the GISTEMP software. We have reported these to Dr Ruedy at NASA GISS who has in all cases fixed them and thanked us for reporting them. The problems we have found either do not affect the published results, or only affect them by tiny amounts, far less than the uncertainty. For instance, one month's reading might change by a hundredth of a degree.

  As our work continues, we have also investigated some questions raised by critics of GISTEMP, for instance whether the warming signal of the results could be due to rounding numbers in the GISTEMP system, or due to the urban heat-island adjustment, or due to changes in weather station numbers in the 1990s. We have been able to show very easily that these factors are not significant—the effect of each factor is tiny, and the effects are often in the opposite direction to that suggested by critics.

  Regarding GISTEMP we conclude:

    — the source code could be clearer;

    — the source code is free of any major errors;

    — it performs as described in the scientific literature;

    — it produces a result which is substantially the same as HadCRUT3, and other similar datasets;

    — the result is also substantially the same when the factors commonly mentioned by critics are removed; and

    — we have no reason to doubt the output of the GISTEMP analysis.

  By "substantially the same" we mean that the conclusions regarding warming in the latter part of the 20th century that one can draw from the GISTEMP analysis are the same as the conclusions one can draw from the HadCRUT3 analysis.

  Of course, none of our work supporting these conclusions would have been possible without the full publication of the original GISTEMP software and the data which it uses.

  If you have any questions regarding this submission, or our work more broadly, we are of course available to give further evidence, in person if necessary.

Nicholas Barnes


David Jones


Ravenbrook Limited

March 2010

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