Carbon
Cycle Science: An FY 2000 Initiative
Rising atmospheric carbon
dioxide concentration and its potential impact on future climate is an
issue of global economic and political significance. The need to understand
how carbon cycles through the Earth system is therefore critically important
to our ability to predict any future climate change. Recent policy debates
have demonstrated the need for a comprehensive, unbiased scientific understanding
of sources and sinks of carbon dioxide on continental and regional scales,
and how sinks might change naturally over time or be enhanced by human
activities. The National Research Council’s report, Global Environmental
Change: Research Pathways for the Next Decade, specifically emphasizes
the need for a comprehensive carbon cycle research strategy.
The USGCRP is answering this call by establishing the Carbon Cycle Science
Initiative. USDA, DOE, DOI, NASA, NSF, DOC/NOAA, and the Smithsonian will
take part in this initiative. The new program is poised to provide critical
unbiased scientific information on the fate of carbon dioxide in the environment
to contribute to the ongoing public dialogue. The program will:
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take advantage of ongoing
breakthrough advances in innovative scientific techniques to measure, monitor,
observe, and model the carbon cycle, making it possible to examine the
carbon cycle comprehensively as an integrated system;
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provide the scientific
foundation for estimating the capacity of land ecosystems and the ocean
to sequester and store carbon dioxide released as a result of human activities;
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integrate modeling, observational,
and process research to identify and quantify regional- to global-scale
sources and sinks for carbon dioxide and other greenhouse gases;
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seek to understand how
these sources and sinks will function in the future and provide this essential
information for future climate predictions; and
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evaluate potential management
strategies for enhancing carbon sequestration in the environment and in
capture and disposal strategies.
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Achieving these objectives
will provide information to policymakers and assist with the planning of
future climate research activities. It will also provide valuable information
to land and forest managers in the public and private sectors, and contribute
to the natural resource management missions of agencies such as USDA and
DOI.
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Full implementation of
the new program will require a significant investment of resources and
a new level of interagency coordination to ensure integration. Implementation
of this program will be closely coordinated with international programs
(e.g., the International Geosphere-Biosphere Programme and the World Climate
Research Programme) to ensure a comprehensive international research strategy.
Background
Carbon dioxide is exchanged naturally between three active
reservoirs: the atmosphere, the ocean, and land ecosystems. Human activity
has increased the amount of carbon dioxide now being exchanged between
these reservoirs. Carbon dioxide is initially added to the atmosphere as
a product of combustion of fossil fuel and as emissions from conversion
of forested land to agriculture. About half of what is added remains in
the atmosphere, and the rest is taken up by the other two reservoirs —
the ocean and land and freshwater ecosystems. Uptake of carbon dioxide
by these reservoirs is commonly referred to as a "sink." While we can measure
the concentration of carbon dioxide in the atmosphere quite accurately,
measurements of storage of carbon in the ocean and land ecosystems are
still considerably uncertain.
For the past decade or more, independent approaches and innovative tools
have greatly increased our understanding of how carbon dioxide is transported
and stored in the Earth system. Most past research has tended to focus,
appropriately, on each component of the carbon cycle separately. However,
the carbon system is fundamentally integrated, and understanding of each
component is now reaching the point where answers are available for how
the carbon cycle operates as an integrated whole. This information is essential
for use in designing and optimizing any potential carbon mitigation strategies
envisioned in the next two decades.
The storage reservoir, or sink, for carbon that we know the least about
is the land ecosystem. Estimates from atmospheric and oceanic data and
models have predicted that the terrestrial sink is larger in the Northern
Hemisphere than in the Southern Hemisphere. Recent studies have attempted
to refine the location of the Northern Hemisphere sink to a continental-scale
region. While there is considerable debate about the magnitude and location
of the terrestrial sink, there is strong evidence that it may be very significant.
However, humans may have inadvertently both created and destroyed terrestrial
carbon sinks in the past from their manipulation of the land surface for
settlement, food and energy production, and water management, for example.
Climate also likely influences the magnitude of both the terrestrial and
the oceanic sink. We have now reached a state of knowledge in the carbon
cycle research arena where we can begin to tackle these questions and provide
unbiased, scientific information to society about the location, magnitude,
and cause of carbon sinks.
Figure 7. Soil
organic carbon in the United States
(See Appendix E
for additional information)
Program
Goal
The overarching goal
of the Carbon Cycle Science Program (CCS) is to answer the following fundamental
questions:
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What has happened to the carbon dioxide that has already
been emitted by human activities (anthropogenic carbon dioxide)?
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What will be the future atmospheric carbon dioxide concentration
resulting from past and future emissions?
FY
2000 Program Highlights
The major focus of
the initiative in FY 2000 will be on determining the location, magnitude,
and cause of carbon sinks in North America, and how North America compares
to other key regions, such as South America. Estimates of the Northern
Hemisphere sink range widely; a program of integrated observations, process
research, and modeling will narrow this range and provide a more accurate
estimate of the North American terrestrial sink and its variability. The
strategy will be to combine appropriate research approaches from the atmosphere,
oceanic, terrestrial, and human dimensions aspects of the carbon cycle,
providing information on various temporal and spatial scales, necessary
to providing an accurate picture of the current state of the terrestrial
carbon sink over North America.
To accomplish these objectives, carbon cycle science research activities
will include:
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Atmospheric and oceanographic
sampling field campaigns over the continent and adjacent ocean basins,
combined with atmospheric transport models to develop more robust estimates
of the continental and subcontinental-scale magnitude and location of the
sink (includes DOE, NOAA, and NSF).
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Local-scale experiments
conducted in various regions that will begin to identify the mechanisms
involved in the operation of carbon sinks on land, the quantities of carbon
assimilated by ecosystems, and how quantities might change or be enhanced
in the future (includes DOE, NSF, Smithsonian, and USDA).
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Evaluation of information
from past and current land-use changes, both from remotely-sensed and historical
records, to assess how human activity has affected carbon storage on land
(includes NSF, NASA, USDA, NOAA, DOI, and DOE).
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Enhanced long-term monitoring
of the atmosphere, ocean, forests, agricultural lands, and rangelands,
using improved inventory techniques and new remote sensing, to determine
long-term changes in carbon stocks (includes USDA, NASA, NOAA, DOE, and
DOI).
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Evaluation of potential
management strategies for maximizing carbon storage, including evaluation
of the variability, sustainability, lifetime, and related uncertainties
of different managed sequestration approaches (includes USDA and DOE).
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Integration of new observations
and understanding of carbon cycle processes in regional and global carbon
system models to improve projections of future atmospheric concentrations
of carbon dioxide and other greenhouse gases (includes DOE, NOAA, NSF,
NASA, DOI, USDA, and Smithsonian).
Understanding from each of
these areas will be synthesized to represent our current state of knowledge
of the carbon system, as well as incorporated into carbon system models,
to provide a best estimate of how carbon sources and sinks may change in
the future. This integrated approach will be the most efficient and effective
way to understand the carbon sink and to provide the most accurate information
on the current state of the sink over North America.
Carbon Cycle Science Initiative
FY 2000 Budget by Agency
(Dollars in Millions)
7.0 DOC/NOAA
14.8
DOE
3.4
DOI
81.1
NASA Space-Based Observations
37.5
NASA Scientific Research
13.1
NSF
0.3
Smithsonian
31.5
USDA
____
_______________
188.7
Total
|
Achieving this task will require new technologies for measuring the atmosphere-land-ocean
carbon system. In addition, the existing observational networks and monitoring
programs will be maintained and enhanced, especially observations of undersampled
aspects of the global CO2
cycle, such as spatial distributions in the atmosphere, ocean temporal
variations, changes of net ecosystem production (e.g., carbon gain), soil
carbon transformations, and land use/vegetation changes in the tropics.
Large-scale observations will be tested with locally-derived process models
and hypotheses about spatial and temporal variability of CO2
exchange among the major Earth system reservoirs. Models to predict carbon
sources and sinks and their interannual/decadal variability (ocean and
land) will be refined, incorporating the most important mechanisms and
providing predictions with enhanced credibility.
Carbon cycle science has a unique opportunity. Exciting techniques and
a new threshold of understanding have paved the way for the next stage
of carbon cycle science in the United States: developing an integrated,
whole system predictive capability for the carbon system. The ultimate
goal is to provide integrated estimates of carbon sources and sinks, with
a focus in FY 2000 on implementing activities to determine the magnitude,
location, and cause of the North American terrestrial sink. The knowledge
base will then be available to provide input on how sinks might be enhanced
and how they might change in the future — information of critical importance
to potential decisions to manage the carbon system.
In FY 2000, activities in the Carbon Cycle Science program will provide
the following results:
A state-of-the-science
report assessing the magnitude, location, and cause of the North American
terrestrial sink from available data, and a research strategy for addressing
uncertainties in the terrestrial sink estimates that are not reconcilable
with current data;
Implementation of integrated
observation, research, and modeling activities to provide more accurate
information on the location, magnitude, and cause of the North American
terrestrial sink based on these identified uncertainties;
A synthesis of global
ocean carbon dioxide data, enabling the design of a research strategy for
monitoring changes and identifying variability in the oceanic sink;
Improved parameterization
of key processes controlling carbon storage, such as air-sea gas exchange,
a major uncertainty in ocean sink estimates;
An improved, long-term,
integrated monitoring strategy for carbon measurements in the atmosphere,
ocean, and land ecosystems.