A new data set of monthly and annual mean surface and upper-air climate data for the Antarctic has been created using in-situ observations. The means were derived from 6 or 12 hourly synoptic observations provided by the Antarctic operators that have been subjected to a rigorous quality control procedure. When synoptic observations could not be obtained CLIMAT messages were used or means provided by the operators. The project is known as READER (REference Antarctic Data for Environmental Research) and is being organised by the Scientific Committee on Antarctic Research (SCAR). The data set is available online at http://www.antarctica.ac.uk/met/READER/ and consists of means of surface temperature and wind speed, mean sea level pressure, and temperatures, heights and wind speeds at standard levels.

Trends at 18 key stations with long records have been examined in detail. The temperature trends indicate the complex nature of the changes that have taken place over the last 50 years, with eleven of the stations having warming trends and 7 cooling trends over their full records. The largest temperature change has taken place on the western side of the Antarctic Peninsula, where Faraday/Vernadsky station has warmed at a rate of 5.6 C/(100 years) on an annual basis (which is as large as any location on Earth) and at 10.9 C(100 years) during the winter, both figures statistically significant at the 5% level. Running thirty year trends of annual mean temperature indicate that at all but two of the 18 stations examined the warming trend was greater (or the cooling trend less) during the 1961-90 period compared to 1971-2000. This points to possible recovery from more extensive sea ice conditions in the 1960s. All the continental stations for which MSLP data were available showed negative trends in the annual mean MSLP over the periods considered, which we attribute to the trend in recent decades towards the Southern Hemisphere annular mode (SAM) being in its high index state. Thirty year trends of MSLP show that for all stations on the Antarctic continent, except Halley, that the trends for 1971-2000 were more negative than for 1961-1990. All but two of the coastal stations have recorded increasing wind speeds over recent decades, which is also consistent with the change in the nature of the SAM.