PROGRAM TITLE: Atmospheric Chemistry Project (IGAC) ACTIVITY STREAM: Process Research SCIENCE ELEMENT:
Biogeochemical Dynamics NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATIONDESCRIPTION: The Project focuses global measurements, lab studies, and theory on improving the understanding of greenhouse gas budgets and stratospheric ozone depletion. Greenhouse Gases. (i) NOAA's global baseline observatories are characterizing the atmospheric trends of major greenhouse gases, e.g., CO2, CH4, N2O, halocarbons, and tropospheric ozone. These studies have recently discovered that the growth rates of CH4 and the halocarbons have slowed. Over the next few years, work will focus on characterizing the terrestrial CO2 sink and the emerging trends of the CFC replacements. (ii) Lab studies are defining the chemical removal reactions (sinks) of radiatively important gases. The residence time (hence Global Warming Potential, GWP) of CH4 was found to be 25% larger than thought, and perfluorocarbons have been shown to be powerful greenhouse gases, with residence times of millennia. (iii) Radiative forcing calculations have discovered that depletion of ozone can cause less radiation to the surface- troposphere system, thereby lowering the CWP's of the CFCs et al. Future calculations are focusing on quantifying, within a year, the effect of ozone depletion on surface temperature and on calculating the net GWPs of the CFCs. Ozone Depletion. (i) Lab studies are providing the atmospheric lifetimes that are needed to determine accurate Ozone Depletion Potentials (ODPs) of the CFC and Halon substitutes and methyl bromide. (ii) Theoretical investigations are developing a refined method of calculating ODPs using atmospheric measurements, rather than purely models. An Overall Performance Measure. A substantial fraction of the new discoveries noted in the Executive Summary of the 1992 IPCC assessment supplement were results from this Project [see pp. 8-9, NOAA Contributions to the 1995 IPCC Assessments (1993)]. STAKEHOLDERS: The Project provides: USGCRP. Ground truth for NOAA/NASA satellites. Collaboration with NSF in studying global chemical sinks and with DOE in tropospheric ozone formation. Partner with NASA in polar ozone campaigns. International. Leader of the North Atlantic Regional Experiment (greenhouse ozone formation) of IGAC and major contributor of two other IGAC efforts. Assessments. Overall assessment, cochair and chairs of 2 chapters of the 1994 Ozone Assessment for the UN Montreal Protocol, cochairs of 2 of the 5 chapters of the 1994 IPCC assessment, and science advisor to the US for the IPCC and Climate Convention. SHORT-TERM POLICY PAYOFFS: Climate Change. Better global trends, sinks, and variations of greenhouse gases, providing insight into budgets and future scenario projections for the Climate Convention. Quantified CFC cooling effect, yielding more accurate predictions of surface-temperature changes. Characterizing tropospheric (greenhouse) ozone, which will help define the relation between pollution abatement and greenhouse-gas abatement. Ozone Depletion. Defining the atmospheric trend response to CFC emission reductions, which can be used to evaluate global compliance. Sounder ODPs for the UN Montreal Protocol and the US Congress, yielding better choices for managing the maximum ozone depletion around the year 2000. Early evaluation of CFC substitutes for industry, thereby avoiding costly plant-investment errors. PROGRAM CONTACT: Dan Albritton, Environmental Research Laboratory,325 Broadway, Boulder, CO 80303, (303-497-5785) and Joel Levy, Office of Global Programs, 1100 Wayne Avenue, Suite 1225, Silver Spring, MD 20910, (301-427-2089 X756).