Search

A companion paper discusses the history of, and rationale for, the development of a CSIRO programme of atmospheric carbon dioxide (CO2) concentration measurements in Australia based on aircraft air sampling, field and laboratory measurements.1 Here, we describe parallel efforts to establish a permanent, ground-based atmospheric Baseline Station at Cape Grim, north-west Tasmania, the political activity required for its establishment, and the work undertaken to select a site commensurate with its long-term objectives. Additional CO2 measurements undertaken to complement the aircraft and Cape Grim measurements are discussed. The development of the Australian Baseline Station was part of an emerging international effort to obtain high-precision measurements of trace gas and aerosol composition of the atmosphere, and to quantify any changes in composition that might be occurring and their possible impact on global climate. We discuss the early development of global carbon cycle models, including the representations of atmospheric transport, and the interpretation of modern atmospheric CO2 data and historic air samples encapsulated in Antarctic ice and firn. The accumulated knowledge from these research activities, together with that collected by international colleagues, forms the basis of our understanding of changes occurring in CO2 concentration. It has contributed to an understanding of the mechanisms of the past and present biogeochemical cycling of CO2, providing predictions of future changes in CO2 concentration. [ABSTRACT FROM AUTHOR]

The potential for carbon dioxide (CO2) in the atmosphere to influence global surface temperatures was first recognized in the mid-nineteenth century. Even so, high-precision measurements of atmospheric CO2 concentration were not commenced until the International Geophysical Year (1957-8), following concerns of the climatic impact of increased use of fossil fuels and the concomitant release of CO2 into the atmosphere. In Australia, an early (1960s-70s) interest in the high-precision measurement of CO2 concentration was stimulated by a study of the photosynthesis and respiration of a wheat crop. This study conducted in north-easternVictoria during 1971-2 led two young CSIRO scientists, J. R. Garratt and G. I. Pearman, encouraged by their Chief, C. H. B. Priestley, to extend micro-environment CO2 studies to larger-scale measurements of CO2 concentration in the background atmosphere. The significant extension of the observation programme required refined measurement techniques to improve both the precision and absolute comparability with observations made by laboratories overseas. Joined in 1974 by P. J. Fraser, they identified the impact of pressure broadening on calibration techniques used in the non-dispersive infrared absorption method of CO2 concentration measurement. This, in turn, led to improved inter-comparability of CO2 concentration data collected around the globe. A comprehensive aircraft-based air sampling programme was established in the early 1970s, leading to increased understanding of the time and space variability of CO2 concentration throughout the depth of the troposphere and lower stratosphere in the mid-latitudes of the Southern Hemisphere. In turn this led to: (i) the establishment of a permanent ground-based observatory at Cape Grim, north-western Tasmania; (ii) the development of carbon cycle models; and (iii) measurements of 12CO2, 13CO2 and 14CO2 relative abundances in current and past atmospheres, the last from air samples trapped in ice cores (described in Part 2, the companion paper). The accumulated data from these studies, together with those collected by international colleagues, form the basis of our understanding of the changes of CO2 concentration over thousands of years. In addition, the data have contributed to our understanding of the mechanisms of past and present biogeochemical cycling of CO2 that provides the predictive basis for future changes in CO2 concentration. [ABSTRACT FROM AUTHOR]