1. Keeling, C. D. et al. in Aspects of Climate Variability in the Pacific and the Western Americas, Geophys. Monogr. 55 (ed. Peterson, D. H.) 165–236 (American Geophysical Union, Washington DC, 1989).
2. Tans, P. P., Fung, I. Y. & Takahashi, T. Science 247, 1431–1438 (1990).
3. Broecker, W. S. & Peng, T.-H. Tracers in the Sea (Lamont-Doherty Geological Observatory, New York, 1982).
4. Liss, P. S. & Merlivat, L. in The Role of Air-Sea Exchange in Geochemical Cycling (ed. P. Buat-Menard) 113–127 (Reidel, Dordrecht, 1986).
5. Keeling, R. F., Bender, M. M., Najjar, R. G. & Tans, P. P. Glob. biogeochem. Cycles (submitted).