April 2008

Climate change detection and indices

Exploring changes in South-East Asia temperature and precipitation extreme indices

WMO facilitates workshops on climate change detection and indices which provide some capacity-building for participants from countries within a data-sparse region. Participants bring a selection of the best meteorological records in their country and, with the supply of freely available software, they have the opportunity to quality-control their data and analyse extreme indices.

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A series of nine such workshops, sponsored by the Expert Team on Climate Change Detection and Indices (ETCCDI), has been held in Jamaica (2001), Morocco (2001), South Africa (2004), Brazil (2004), Turkey (2004), Guatemala (2004), India (2005), the Democratic Republic of Congo (2007) and Viet Nam (December 2007). The ETCCDI brings together experts from the WMO Commission for Climatology, the Climate variability and predictability study (World Climate Research Programme) and the Joint Technical Commission for Oceanography and Marine Meteorology (WMO-Intergovernmental Oceanographic Commission of UNESCO).

Seventeen participants from 11 countries in the South-East Asian region (Bhutan, Cambodia, Fiji, People’s Democratic Republic of Laos, Maldives, Myanmar, Nepal, Sri Lanka, Thailand, Timor leste and Viet Nam) attended the Viet Nam workshop. They brought daily data from at least one station in their country.

There were talks about the benefits of a regional approach to climate change and a a history of the ETCCDI workshops was presented, together with some relevant results for climate change in the region following an overview of the IPCC Fourth Assessment Report. WMO’s representative at the workshop gave a talk on climate data and information and development challenges including key climate issues, WMO’s role and programmes on climate.

Participants were introduced to general theory on quality control and the specifics of how it worked in the workshop softwareand the importance of homogeneity in data analysis. After an introductory talk, they started the process of checking their data for homogeneity. A presentation was given on work to develop improved tropical cyclone datasets—a topic of interest to many countries in the region.

The indices to be used in the data analysis were discussed, after which the participants were able to generate the indices for their stations and calculate trends if their time series were long enough. Participants presented their results and the trends were gathered together.

pile of paperNguyen Dang Que, deputy director of the Hydrometeorological Data Centre, invited participates to visit the archive, where great care has been taken in looking after the meteorological records. Most of these are still in paper form, as is common in the region, but staff are in the process of digitizing them.

For the workshops to be a continued success, it is important that a peer-reviewed publication is produced with the results from the workshop. Moreover, the indices data need to be shared with the international research community in order to continue to advance our understanding of variations and trends in climate extremes. Post-processing is invariably necessary since one week is not usually enough to perform a full quality control on all one’s data. Experience has shown that participants are willing to allow one person access to the raw daily data for the purposes of writing the paper on the understanding that this is the only purpose for which data will be used. The countries involved with this workshop were especially helpful in making their data available.

In addition to their specific goal of collating information relevant for assessing climate change in a region, this workshop, as with other previous workshops, was useful in providing training to participants in other aspects of climate data analysis, such as data homogeneity and the importance of metadata. The capacity of NMHSs in the region varies greatly, as does the availability of data. Some participating countries had records extending for a century or more, while others only had data for the last 5- 10 years (although archives from former colonial countries may provide scope to extend some of those records). Even those countries whose datasets were too short to contribute to an analysis of trends were able to make useful contributions, especially in assessing the effects of the 1997/1998 El Niño event, which had a major impact on temperature and rainfall in many parts of the region.

A detailed list of the areas where improvements could be made to the software was made and a report sent to the developers.

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An example of some of the trends obtained from the workshop for warm nights. Note that these are the results prior to the post processing that will be performed for peer-reviewed scientific publication.

More information on the work of the Expert Team can be found at http://www.clivar.org/organization/etccdi/etccdi.php. Detailed information on the workshop software and indices from previous workshops are available from http://cccma.seos.uvic.ca/ETCCDI/. It is the aim that the indices from this workshop will also appear on the Website when quality control is fully completed.

Lisa Alexander, Blair Trewin and John Caesar

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