Atmospheric Chemistry in a Changing World An Integration and Synthesis of a Decade of Tropospheric Chemistry Research

1 Changes in the Chemical Composition of the Atmosphere and Potential Impacts.- 1.1 Introduction.- 1.2 Global Atmospheric Chemistry and the IGACProject.- 1.3 Past Changes in Atmospheric Chemical Composition.- 1.4 Causes of Atmospheric Changes.- 1.5 Impacts of Changes in Atmospheric Composition.- 1.6 Some Important Questions.- 2 Biosphere-Atmosphere Interactions.- 2.1 Introduction.- 2.2 KeyBiogenicGasesor Familiesand their Relevance to Atmospheric Chemistry.- 2.3 A Paleoclimatic Perspective on CH4 and DMS.- 2.4 Atmospheric Compounds as Nutrients or Toxins.- 2.5 Approaches for Studying Exchange.- 2.6 Terrestrial Highlights.- 2.7 Background: Emissions and Deposition.- 2.8 Marine Highlights.- 2.9 Summary of Achievements and Remaining Research Challenges.- 3 Atmospheric Photooxidants.- 3.1 Introduction.- 3.2 Ozone Precursors.- 3.3 Photochemistry in the Troposphere.- 3.4 Transport and Mixing Processes.- 3.5 A Climatology of Tropospheric Ozone.- 3.6 Long-Range Transport of Pollution and Impact on the Ozone Budget.- 3.7 Summary of Principal Achievements and Remaining Uncertainties.- 4 Tropospheric Aerosols.- 4.1 Introduction.- 4.2 Integrated View of the Present State of Knowledge of Atmospheric Aerosols.- 4.3 Selected Recent Developments.- 4.4 Research Approaches.- 4.5 Highlights and Remaining Challenges.- 5 Advances in Laboratory and Field Measurements.- 5.1 Introduction.- 5.2 Laboratory Studies.- 5.3 Field measurements: Gas Phase.- 5.4 Field measurements: Aerosols.- 5.5 Satellite Instruments for Tropospheric Chemistry.- 5.6 Long-Term Measurements.- 5.7 Summary and Conclusions.- 6 Modelling.- 6.1 Introduction.- 6.2 Types of Models.- 6.3 Model Components.- 6.4 Model Evaluation.- 6.5 Model Applications.- 6.6 Current Developments and Future Challenges.- 7 An Integrated Viewof the Causes and Impacts of Atmospheric Changes.- 7.1 Introduction.- 7.2 What Determines the Chemical Composition of the Atmosphere?.- 7.3 How Have Human Activities Altered Atmospheric Composition?.- 7.4 How Have Human Activities Changed the Global Atmospheric Budgets of Carbon, Nitrogen, and Sulphur?.- 7.5 What Controls Tropospheric Ozone?.- 7.6 Is the “Cleansing Efficiency” of the Atmosphere Changing?.- 7.7 How Does Atmospheric Chemistry Affect the Biosphere and Food Production?.- 7.8 How Does Atmospheric Chemistry Affect Human Health?.- 7.9 What is the Connection between Atmospheric Composition and Climate?.- 7.10 How Might Chemical Composition Evolve in the Future?.- 7.11 Are There Risks of Abrupt Changes and/or Irreversible Changes in Atmospheric Composition?.- 7.12 What Should the Research Strategy Be to Address Unresolved Questions?.- References.