Air samples are analysed at CGBAPS to determine both the composition and chemistry of our atmosphere and how it is changing over time. Also measured are weather and climate indicators like wind speed and direction, rainfall, temperature, humidity and solar radiation.
The long-lived greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and synthetic GHGs such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6), are a core part of the measurement program. Chemicals which deplete the ozone layer (called ozone depleting substances or ODSs) are also measured, for example chlorofluorocarbons (CFCs) and halons, which are themselves potent GHGs. The number of atmospheric GHGs & ODSs measured at Cape Grim now exceeds 80.
Other core compounds measured at CGBAPS are aerosols including black carbon, reactive gases including tropospheric ozone, nitrogen oxides, volatile organic compounds, radon (an indicator of recent terrestrial influences), solar radiation, rainfall chemical composition, mercury, and persistent organic pollutants (POPs).
The Cape Grim Science Program originated from a commitment by the Australian Government to the United Nations Environment Program in the early 1970s to monitor and study global atmospheric composition for climate change purposes as a result of human activities and natural variability. As a result, the Cape Grim Baseline Air Pollution Station (CGBAPS) first began measuring the composition of the atmosphere in April 1976 and has been in continuous operation since that date. Located on the north-west tip of Tasmania, Cape Grim BAPS is able to measure ‘true background’ air – air that is uncontaminated by point sources – when the wind blows in to the south-west sector from across the Southern Ocean.
The Cape Grim Baseline Air Pollution Station is a joint responsibility of the Australian Bureau of Meteorology (BoM) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The BoM funds and operates the CGBAPS, and partners with CSIRO to manage the science program, in collaboration with the University of Wollongong and the Australian Nuclear Science and Technology Organisation In collaboration with other institutions, CSIRO scientists analyse and model the resultant data, which are made publically available for use by Australian Government agencies, industry, citizens and international agencies.
Together with the stations at Mauna Loa in Hawaii and Alert in the Canadian Arctic, CGBAPS is one of three premier Baseline Air Pollution Stations in the World Meteorological Organization-Global Atmosphere Watch (WMO-GAW) network.
Some of the air samples collected at Cape Grim have been archived for future analyses. The Cape Grim Air Archive commenced in 1978 and is invaluable in determining changes in the historical abundance of a wide range of gases. For some of these gases, accurate and precise analytical methods only evolved well after they first appeared and began accumulating in the atmosphere (for example HFCs and PFCs).
The measurements are state-of-the-art in precision and accuracy. They are used to identify trends in trace gases and particles in the Southern Hemisphere, which are then used to validate and drive Earth System models and to identify processes that cause changes in the climate system.
Most GHGs (for example carbon dioxide, nitrous oxide, HFCs, PFCs, sulfur hexafluoride) have shown continuous increases in concentration since the mid-to-late 1970s. However for some GHGs that are also ozone depleting substances, such as CFCs and halons, and thus banned under the Montreal Protocol, measurements show that their abundance in the atmosphere is now declining.
Since the station first began measurements in 1976, carbon dioxide levels have increased by more than 20 per cent. Concentrations of methane and nitrous oxide at Cape Grim have also increased significantly since 1978 by about 23 and 10 per cent respectively. These increases are caused by human activities such as fossil fuel use and various agricultural practices.
Cape Grim data are freely available from major global data archives. They have been widely cited in all 5 international assessments of climate change by the Intergovernmental Panel on Climate Change (1990–2013), in all 11 international assessments of ozone depletion from the United Nations Environment Programme and World Meteorological Organization (1985–2018), in all 5 Australian State of the Climate reports (2010, 2012, 2014, 2016, 2018), and in tropospheric ozone assessments.
Cape Grim data are also used by the Australian Government to meet international obligations. For example, Cape Grim greenhouse gas data have been used to provide independent verification of components of Australia’s National Greenhouse Gas Inventory, which reports Australia’s annual emissions to the United Nations Framework Convention on Climate Change (UNFCCC); Cape Grim POPs data have been reported to the Stockholm Convention on Persistent Organic Pollutants; and Cape Grim mercury data have been reported to the Minamata Convention on Mercury. Cape Grim ODS data are also used to track the efficacy of the Montreal Protocol on Substances that Deplete the Ozone Layer.
Cape Grim BAPS data have also been used in hundreds of research papers on climate change and atmospheric pollution. Through its work with universities, Cape Grim BAPS is a training ground for the next generation of climate scientists.
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