Updates

8th May 2003
This data-set has been superseded by the updated version, TYN CY 1.1.

10th February 2003
1. A table is available, accessible via 'Data' on the left frame, that summarises the full range of data-sets available.
2. A new country-by-country climate data-set has been added, presenting information on modelled climate changes during the 21st century. See TYN CY 3.0.

21st August 2002
The Climatic Research Unit and the Tyndall Centre are currently re-organising the dissemination of data-sets. As part of this re-organisation, related data-sets are being labelled under a consistent scheme of acronyms. We urge users of these data-sets to use these acronyms wherever possible, to enable the data-sets that they have used to be identified clearly and unambiguously. This data-set is now labelled TYN CY 1.0.

19th August 2002
1. A page has been added giving examples of published academic work that uses the country climate data-sets. I welcome the opportunity to add details of your work (see the page for details)!
2. I have added an electronic version of the paper describing the observed country climate data, which was published in a peer-reviewed journal called Area.
3. The corrected cloud time-series files are now available.

26th July 2002
Errors have been found in the cloud time-series files. These have therefore been withdrawn. The corrected version is expected in late August 2002.

27th May 2002
A new country-by-country climate data-set (TYN CL 2.0) has been added to my website, presenting information on modelled climate changes during the 21st century. The new data-set has not yet been approved by the IPCC-DDC; therefore it does not constitute part of the IPCC-DDC website, nor is it recommended for use by the IPCC-DDC, unlike the observed data provided on this page.

23rd April 2002
1. The attribution has been updated, to: Mitchell,T.D., Hulme,M., and New,M., 2002: Climate data for political areas. Area 34:109-112.
2. The units of two of the variables have been changed: frost day frequency and wet day frequency are now given in days, rather than days/month.
3. The units of precipitation are now millimetres consistently across the data-set.

Introduction
The data set described here provides a summary of the climate of the 20th century for 289 countries and territories.

• The primary product is the average climate in the recent past (1961-1990), which is supplied for nine climate variables.
• A secondary product is the set of year-by-year variations over the 20th century (1901-1998), which is supplied for seven climate variables.

• each calendar month (January-December),
• each climatic season (March-May, June-August, September-November, December-February),
• the calendar year (January-December).

Guidance
This data set is intended for use in trans-boundary research, where it is necessary to average climatic behaviour over a wide area into statistics that are representative of the whole area. The user should note that any single country may contain substantial spatial variations of climate within it, and that climate changes over time.

This data set should not be used to represent climate at a point, or for sub-regions of the countries and territories supplied here. If climate data is required for points or sub-regions, enquiries should be made to the national meteorological agency of the country concerned.

The credibility of the data set rests upon the work of others, who have made the observations and placed them on to a half-degree grid covering the globe (see details of the original data). The work of this author was to aggregate the grid box values into averages representing countries and territories (see details of the data processing).

For many countries, the accuracy is better for more recent decades than for earlier decades of the 20th century (although data is provided wherever possible). In addition, the useful precision of the data may be less in earlier decades of the 20th century (although the recorded precision is constant throughout). For some variables and countries there is insufficient data to make a reasonable estimate of year-to-year variations in the early part of the 20th century; in such cases, the values recorded are 'relaxed' towards the average from 1961-1990, and therefore are not representative of the real-world year-to-year variations.

One climatic season (December-February) overlaps from one calendar year to the next. The value we supply begins in the December of the year recorded, and ends in the February following the year recorded. Therefore the last year recorded always contains the missing value (-999.0) in the DJF column.

Further information may be obtained from the research paper published in Area. An electronic version is available.

Data Structure
The TYN CY 1.0 data-set has now been superseded by the updated version, TYN CY 1.1. Therefore although the documentation is still available, the data has been withdrawn from the public domain. Users should adopt TYN CY 1.1 instead, which includes all the information available under TYN CY 1.0, and additional information.

Ownership
The creator of this data set (Dr. T. D. Mitchell) retains full ownership rights over it. The data set may be freely used for non-commerical scientific and educational purposes, provided it is described as TYN CY 1.0 and attributed to the following publication (available here):
Mitchell,T.D., Hulme,M., and New,M., 2002: Climate data for political areas. Area 34:109-112.

Disclaimer
The author bears no responsibility for the accuracy of the data set. The countries listed below include a variety of sovereign states, dependent territories, and disputed territories. No political statement is being made by the inclusion or exclusion of a particular territory, or by the labelling of a particular territory by a particular name.

Data Processing
The original data took the form of a value for each month and each box on a 0.5 degree latitude / longitude grid. We assigned each box to a single country. For each country we calculated the weighted mean of the values from its constituent grid boxes for each month in turn. Each grid box was weighted by surface area, using the cosine of the latitude. The seasonal and annual values are the means of their constituent months.

Original Data
Station observations were first collected by national meteorological, hydrological and related services, and were acquired through the free and unrestricted exchange of meteorological and related data. These observations were gridded by collaborators at the Climatic Research Unit. The gridded data-set is publicly available, and has been published in a peer-reviewed scientific journal:
New, M., Hulme, M., and Jones, P., 1999: Representing twentieth-century space-time climate variability. Part I: Development of a 1961-1990 mean monthly terrestrial climatology. Journal of Climate 12: 829-856