Monday, June 30, 2014

Global Land Surface Databank: Version 1.0.0 Release

The International Surface Temperature Initiative is pleased to release version 1 of a new monthly dataset that brings together new and existing sources of surface air temperature. Users are provided a way to more completely track the origin of surface air temperature data from its earliest available source through its integration into a merged data holding. The data are provided in various stages that lead to the integrated product. 

This release is the culmination of three years effort by an international group of scientists to produce a truly comprehensive, open and transparent set of fundamental monthly data holdings. The databank has been previously available in beta form, giving the public a chance to provide feedback. We have received numerous comments and have updated many of our sources. 

This release consists of:
  • Over 50 distinct sources, submitted to the databank to date in Stage 0 (hardcopy / image; where available), Stage 1 (native digital format), and Stage 2 (converted to common format and with provenance flags).
  • All code to convert the Stage 1 holdings to Stage 2.
  • A recommended merged product and several variants which have all been built off the Stage 2 holdings. 2 ASCII formats are provided (ISTI format, GHCN format), along with a CF Compliant netCDF format.
  • All code used to process the data merge, along with statistical auxiliary files.
  • Documentation necessary to understand at a high level the processing of the data, including the location of the manuscript published in Geoscience Data Journal.
The entire databank can be found here and the merged product is located here. Earlier betas are also found here. Because the databank is version controlled, we welcome any feedback. We will be providing updates on the blog regarding any new releases.
  • For more information, please visit our website:
  • General Comment? Please email

Location of all stations in the recommended version of the Stage Three component of the databank. The color corresponds to the number of years of data available for each station.

Station count of the recommended merge by year from 1850-2010. Databank stations in red compared to GHCN-M, version 3 in black.

Saturday, June 28, 2014

Understanding the effects of changes in the temperature scale standards through time

Since records of surface temperature started being made there have been iterations of the fixed points standards used by national metrological institutes (that is not a typo). Assuming that all meteorological measurements through time have been made to such standards (which may be a considerable stretch) this would have imparted changes to the records that are not physical in origin. As part of meteomet efforts have been made to understand this. It is a relatively small effect compared to effects of other long recognized data issues. Nevertheless it is important to properly and systematically consider all sources of potential biases as exhaustively as possible.

The work itself was led by Peter Pavlasek of the Slovak Institute of Metrology. His introduction is reproduced below:
Temperature is one of the main quantities measured in meteorology and plays a key role in weather forecasts and climate determination. The instrumental temperature recordings now spans well over a century, with some records extending back to the 17th century, and represents an invaluable tool in evaluating historic climatic trends. However, ensuring the quality of the data records is challenging, with issues arising from the wide range of sensors used, how the sensors were calibrated, and how the data was recorded and written down.  In particular, the very definition of the temperature scales have evolved. While they have always been based on calibration of instruments via a series of material phase transitions (fixed points), the evolution of sensors, measuring techniques and revisions of the fixed points used has introduced differences that may lead to difficulties when studying historic temperature records. The conversion program here presented deals with this issue for 20th century data by  implementing a proposed mathematical model to allow the conversion from historical scales to the currently adopted International Temperature Scale of 1990 (ITS-90). This program can convert large files of historical records to the current international temperature scale, a feature which is intended to help in the harmonisation processes of long historic series. This work is part of the project “MeteoMet” funded by the EURAMET, the European association of National Institutes of Metrology, and is part of a major general effort in identifying the several sources of uncertainty in climate and meteorological records.

Michael de Podesta, who has served on the steering committee since ISTI's inception, reviewed the software for ISTI and had the following summary:
Assuming that calibration procedures immediately spread throughout the world – homogenisation algorithms might conceivably see adjustments in 1968, with smaller adjustments in 1990.
If undetected, the effect would be to create a bias in the temperature record. This is difficult to calculate since the bias is temperature dependent, but if the mean land-surface temperature is ~10°C and if temperature excursions are typically ±10 °C then one might expect that the effect to be that records prior to 1968 were systematically overestimated by about 0.005 °C, and records between 1968 and 1990 by about 0.003 °C.

Michael's full summary which includes some graphical and tabular summaries can be found here.

The code package is a windows operating system based package. It is available here.

Wednesday, June 4, 2014

Paper describing benchmarking concepts in OA review

Just briefly to note that a discussion paper is now open for comment authored by the members of the benchmarking working group. This paper discusses the concepts and frameworks that will underpin all aspects of the benchmarking and assessment exercise. Its open to review until July 30th. Please do, if you have time and inclination, pop along and have a read and provide a constructive (!) review. The discussion site is at .

Also, watch this space at the end of this month for exciting developments on the first pillar of the ISTI framework - the databank.

Finally, we are rapidly hurtling towards the SAMSI/IMAGe/ISTI workshop on surface temperatures and their analyses. Its going to be a busy few weeks so expect this blog to be somewhat less moribund than of late ...