Half Mace is the postal address, but 53 degrees 20 minutes north, nine degrees 54 minutes west gives an idea of its westerly location. Forty years ago the site housed a coastal lookout post, but now the Mace Head Atmospheric Research Station is one of the important bases of its type in the northern hemisphere.
Situated some four miles towards the Atlantic beyond Carna, Co Galway, the extensive refurbishment of what was a derelict cottage looks modest enough. However, this image belies the fact that the complex represents a vital link in the World Meteorological Organisation's Global Atmospheric Watch network, which stretches from Ushuaia in Argentina to Ny Alesund on Norwegian Spitsbergen.
Last Friday the Minister for the Environment, Mr Dempsey, paid tribute to its role when he marked the 40th anniversary of the station's first measurements with a visit.
Its importance was already noted earlier this year, when Dr John Miller of the World Meteorological Organisation spoke of its work at a conference on atmospheric science and global change in NUI Galway.
The station picks up the first air travelling across the Atlantic to Europe on prevailing westerly winds. The relatively low levels of pollution carried enable crucial baseline data to be set.
Since 1987, for instance, Mace Head has been one of five sites in the world studying the life times of chlorofluorocarbon (CFC) gases in the atmosphere as part of the Advanced Global Atmospheric Gases Experiment (GAGE).
From 1987 to 1994 it was also one of four primary sites for the Atmosphere Ocean Chemistry Experiment on biogeochemical cycles in the North Atlantic, funded by the US National Science Foundation.
In 1994 and 1995 NUI Galway co-ordinated an EU-funded project to assess background maritime contribution to European atmospheric pollution; from 1987 it has been part of the European Tropospheric Research (TOR) network, and it still contributes to European and American studies of ground-level ozone concentrations.
A bilateral Irish-German scheme in the past decade has conducted extensive studies of heavy metals in the atmosphere, including elemental mercury. There are continuing studies of methane and carbon dioxide, including collection of flask samples which are analysed for isotopic constitution to trace their origin to fossil fuels or recent organic processes. The station also collects flask samples for the American NOAA long-term air sampling network.
The facilities have been used by scientists from about 100 universities and institutions in some 20 countries, and over 40 international scientists are currently conducting an intensive field campaign on the role of atmospheric aerosols, funded by the EU. Aerosols are fine particles which influence air pollution, climate and health and can contribute to respiratory problems and other adverse physical conditions.
There is a national dimension to its programmes. Galway scientists have specialised in the study of particulate matter in the atmosphere, such as the very small Aitken or condensation nuclei formed by combustion processes and gaseous reactions, the larger particles or cloud condensation nuclei on which cloud droplets form and particles of black carbon soot and of organic origin.
The condensation nuclei concentrations can vary from less than a hundred to more than a million per cubic centimetre, and are good indicators of clean maritime or polluted continental air.
The station/laboratory is run by a management committee of staff from the Department of Physics at NUI Galway. The scientific input makes a considerable contribution to the local economy, according to the university.
"Pollution does not recognise state boundaries, and emissions in one area can be transported around the world in a matter of days," Prof Gerard Jennings, of the Department of Experimental Physics at the university, said.
Together with Dr Aodhagan O Rodaigh and Dr Tom O'Connor, he heads the research team. He stresses that continuous measurement at Mace Head is necessary to determine long-term trends in atmospheric pollutant levels. International conventions are also influencing change, he said, and this can be detected by equipment at the research station. For instance, measurement of CFCs and their substitutes are taken by an automated gas chromatograph-mass spectrometer, the first introduced to a field station worldwide when installed in 1995.