622551keelingvol4.jpg For more than a decade, my research group has been engaged in measuring changes in atmospheric oxygen (O2) concentration. Oxygen is closely linked to carbon dioxide by photosynthesis, respiration, and combustion reactions. We have shown that oxygen concentrations in the clean atmosphere vary with season and are slowly decreasing from year to year. By measuring these changes along with changes in carbon dioxide, we can learn about the fate of the carbon dioxide emitted each year by humans: How much remains in the air? How much enters the oceans? How much is taken up by land plants? Recently, I have also been engaged in developing theories for why atmospheric carbon dioxide was lower during Pleistocene glacial periods, and why the global climate was also highly unstable during these times. E-mail: rkeeling@ucsd.edu

"A broad overview of specific themes and enquiry methods for biogeochemists and atmospheric geochemics. ...A huge amount of material has been brought together in the book and synthesized by the well-know and active practitioners in the field. It is highly recommended." --Shaocai Yu, PhD, National Exposire Research Laboratory, US Environmental Protection Agency, NC, USA

• 1. Oxidative capacity, ozone source/sinks, constraints on OH abundance (R.G. Prinn). 2. Geochemistry of reactive nitrogen species. 3. Geochemistry of atmospheric methane (W.S. Reeburgh). 4. Tropospheric halogen chemistry (P.J. Crutzen, R. von Glasow). 5. Non-mass dependent isotopic fractionation: mechanisms and applications (M.H. Thiemens). 6. Isotopic composition of atmospheric CO2 and O2 (D. Yakir). 7. Radiocarbon (W.S. Broecker). 8. Atmospheric water isotopes (J. Jouzel). 9. Aerosol chemistry. 10. Tropospheric aerosol composition and properties (P.R. Buseck, S.E. Schwartz). 11. Biomass burning (J.S. Levine). 12. Tracers of atmospheric circulation (M. Heimann). 13. Atmospheric radionuclides other than 14C (K.K. Turekian, W.C. Graustein). 14. Chemistry of the stratospheric ozone layer (J.M. Rodríguez). 15. Stratosphere-troposphere exchange (K.A. Boering). 16. Planetary degassing (D.R. Porcelli, K.K. Turekian).