Organization: Department of Commerce (DOC)

Research Title: Atmospheric Chemistry Project

Funding Level (millions of dollars):

FY94 7.3
FY95 7.2
FY96 6.4

Committee on Environment and Natural Resources (CENR) Component:
(a) Subcommittee: Global Change Research Subcommittee (100%)
(b) Environmental Issue: Climate Change (50%); Ozone and Ultraviolet Radiation (50%) System Structure and Function (Processes) (90%); Comprehensive Assessment (10%)
(c) Research Activity: System Structure and Function: Prediction (100%)

Organizational Component:
Office of Global Programs
NOAA Aeronomy Laboratory
Mail Code R/E/AL
325 Broadway
Boulder, CO 80303

Point of Contact:
Daniel L Albritton
Phone: 303-497-5785

Research Goals:
To improve the understanding and prediction of the global trends, controlling processes, and radiative impacts of (i) greenhouse gases, notably carbon dioxide, methane, nitrous oxide, halocarbons, and tropospheric ozone, and, also, aerosols; and (ii) chemicals that deplete the stratospheric ozone layer, in both polar regions and globally, and the relation of ozone losses to climate change.

Research Description:
The project focuses an integrated effort composed of global time-series measurements (20%), process-oriented lab and field studies (60%), and theory and modeling (20%) on improving the understanding of greenhouse-gas and aerosol budgets, stratospheric ozone depletion, and their relation to the radiation budget.

Greenhouse Gases and Aerosols. (i) NOAA's global baseline observatories are characterizing the atmospheric trends of major greenhouse gases. These studies have discovered recently that the growth rates of carbon dioxide, methane, and nitrous oxide, which had recently been anomalously slow, have begun to return to earlier growth rates, and that the halocarbon growth rates have slowed as expected in accordance with international restrictions on their production. Over the next few years, expanded work will focus on characterizing the terrestrial carbon dioxide sink. (ii) Lab studies are defining the chemical removal reactions (sinks) of radiatively important gases, and the perfluorocarbons (PFCs) have been shown to be powerful greenhouse gases, with residence times of millennia. (iii) Field studies have a major emphasis in the North Atlantic Ocean where the regional-to-global scale processes could be a key to characterizing the formation of upper tropospheric ("greenhouse") ozone, and the Equatorial Pacific Ocean where background processes can be characterized. (iv) Radiative forcing calculations have discovered that both the depletion of ozone and the presence of aerosols in the atmosphere can cause less radiation to reach the surface-troposphere system and gaining a more quantitative understanding will be the focus of increasing research emphasis in coming years.

Ozone Depletion. (i) Monitoring of background ultraviolet radiation will be added to the long-term ozone monitoring at Mauna Loa Observatory, in collaboration with New Zealand, and the ground-based efforts will focus on a better definition of the emerging trends of the chlorofluorocarbon (CFC) replacements. (ii) 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. (iii) Airborne field campaigns, in collaboration with NASA and others, are addressing polar ozone-loss processes and their potential roles in contributing to the observed downward trends in mid-latitude ozone in both hemispheres. The emphases are on assessing the vulnerability of the Arctic during the coming decade when chlorine levels will peak and on helping (with NASA) assess the environmental impact of aircraft, both supersonic and subsonic. (iv) Theoretical investigations are focusing on the possible causes of the global downward trends in lower stratospheric ozone, on attribution of the causes, and on their relation to climate change.

The project is supporting both in-house NOAA laboratory research activities and non-Federal (largely academic) research investigations.

Program Interfaces:
The Project's research is a part of or coupled with national and international activities:

Program Milestones:
Summer, 1995. Updated Global Warming Potentials (GWPs) for the 1995 comprehensive assessment of climate change by the Intergovernmental Panel on Climate Change. Summer, 1996. International field campaign in the North Atlantic Ocean to characterize ozone forming processes in the Northern Hemispheric mid-troposphere. Summer, 1997. International field campaign in the North Atlantic Ocean to characterize the impact of anthropogenic aerosol emissions on climate.

Policy Payoffs:
Climate Change. Better understanding of global trends, sinks, and variations of greenhouse gases and aerosols, providing insight into budgets and improved future scenario projections for ongoing meetings of the Climate Convention. Quantified CFC cooling effect, yielding more accurate predictions of surface temperature changes which will aid the attribution of the causes of climate change. Characterization of tropospheric (greenhouse) ozone, which will help define the relationship between pollution abatement and greenhouse gas abatement, and provide a more-complete description of the changes in radiative forcing. 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 recovery from maximum ozone depletion expected around the year 2000. Early evaluation of CFC substitutes for industry, thereby avoiding costly plant-investment errors.