PROGRAM TITLE:	Carbon Cycle Research
ACTIVITY STREAM:	Processes, Modeling, Assessment
SCIENCE ELEMENT: 	Biogeochemical Dynamics, Human Dimensions


DESCRIPTION:  Goals are to understand and model changes of CO2 
concentration caused by natural and human-induced activities.  Objectives 
are to: 1) document fossil fuel and biospheric emissions of CO2; 2) observe 
atmospheric CO2 change; 3) understand processes affecting CO2 retention in 
the atmosphere, including controls on atmosphere-ocean and atmosphere-
land CO2 exchange.  Data bases on carbon emissions, fluxes and storage are 
assembled, from which models are developed, tested and used to predict 
future atmospheric CO2 concentration and rates of change.  Products from 
emissions research are integrated data bases on global fossil fuel CO2 
emissions (e.g., Rotty and Marland), and calculated future CO2 emissions 
using the Second Generation Model (Edmonds).  Estimated biosphere CO2 
source is based on Houghton's analysis, which uses field data on biomass 
density and historical land-use change data (Brown, Richards and others).  
These combined efforts produce the integrated time trend of CO2 emissions, 
which is the greenhouse gas forcing used in GCM studies of climate 
sensitivity.  Continued research improves the geographic detail of the data 
bases, and produces reliable greenhouse gas scenarios for integrated studies of 
carbon cycle, climate and ecosystem response to greenhouse gases emissions.  
Scientific products from atmospheric CO2 and global carbon cycle modeling 
include CO2 measurements of atmospheric CO2 change (i.e., the Keeling data 
base as a touchstone of the Global Change Program), and the modeling of 
physical, chemical and biological processes governing CO2 change.  Data and 
models provide the framework for scientific evaluations of rate and amount 
of atmospheric CO2 increase, and for determining what happens to the excess 
CO2 from fossil fuel and deforestation.
STAKEHOLDERS: International measurement and modeling communities 
(both scientific and institutional bodies) rely on "Keeling" atmospheric CO2 
data. Real-time emissions data and the "Edmonds Second Generation Model" 
are the basis for emissions projections of many integrated and worldwide 
assessments (e.g., IPCC).  Combined with reduced-form carbon cycle and 
climate models, these efforts are the foundation for an "Integrated Climate 
Change Assessment Model (ICCAM)" - jointly carried out by industry and the 
federal government.  These are important ingredients of the USGCRP's 
integrated assessment program.
SHORT-TERM POLICY PAYOFFS:  The research is directly relevant to the 
central question of how CO2 generated by human activities contributes to 
global changes in the atmosphere, biosphere and climate.  Carbon cycle 
models and energy-economic-ecologic data bases and models are used in real-
time analysis of policy issues; carbon density data bases are used to quantify 
sources and sinks of CO2, and the integrated carbon cycle models contribute to 
Integrated Assessments of greenhouse gases and climate change.  The 
combined models are primary tools for predicting future atmospheric CO2 
concentrations, and for evaluating impacts of mitigative actions for 
greenhouse gases and energy policy decisions, e.g., for defining mitigation and 
management strategies and alternative technologies for controlling 
greenhouse gas emissions.  This combination of models is the near-term 
methodology for policy analysis of CO2 stabilization scenarios.  Products 
contribute to both National assessments and to the IPCC.  In the future, as 
greenhouse gas mitigation steps are adopted, atmospheric CO2 measurements 
and the global data base will become increasingly important for evaluating 
the effectiveness of policy actions.
PROGRAM CONTACT:  Roger C. Dahlman, DOE, ER-74, Washington, DC 
20585, 301-903-4951