Among the many motives for interest in the carbon cycle
(policy, economic, scientific, management, sustainable development,
public/societal), three provide compelling reasons for the establishment
and operation of global, systematic, long-term observations of the carbon cycle
and the associated aspects in the terrestrial and atmospheric domains:
- Policy imperative for a global carbon observing system has been well
established. Through international negotiations, national governments
have agreed to numerous conventions and multilateral agreements that specify
or imply the need for carbon cycle information and therefore systematic, long-term
observations (GTOS, 2000; GOOS, 1998). At the present time, the relevant conventions
include: the Framework Convention on Climate Change (UNFCCC) and the associated
Kyoto Protocol; the Convention on Biological Diversity; the Convention to
Combat Desertification; Agenda 21 (agreed to at the 1992 United Nations Conference
on Environment and Development); and the Global Plan of Action for the Protection
of the Marine Environment from Land-Based Activities. These and other conventions
identify needs and objectives to be satisfied through co-ordinated international
efforts.
To meet their obligations under the conventions, national governments and
international organisations need sound, consistent information on the terrestrial
and atmospheric aspects of the carbon cycle and the factors that affect it.
For example, land cover and use as well as their changes are essential to
most of the conventions. Conventions require assessments of the current status,
detection and projection of trends, and the implications from a policy perspective.
Such evaluations are conducted for example by the Intergovernmental Panel
on Climate Change in response to policy needs, based on published results
of analyses that in turn depend on systematic global observations. It should
be noted that the conventions also make provisions for observations; for example,
UNFCCC (COP 5) has called on Parties to undertake systematic observation and
research. UNFCCC requires transparent and verifiable reporting, and this will
likely also apply to the Kyoto Protocol. A globally consistent, data-based
approach such as proposed for the terrestrial carbon theme (section 4.) is
well suited to satisfy this requirement.
It is important to note that while recent policy discussions have concentrated
on the potential role of specific terrestrial sinks, the fundamental policy
issue is the impact of increasing atmospheric concentration of trace gases.
The increase depends on the uptake by the entire biosphere and is modulated
by local land use actions. Improved understanding of the carbon cycle also
necessitates consideration of the biosphere as a whole (IGBP Carbon Working
Group, 1998; see also below). For these and other reasons, the proposed concept
for terrestrial carbon observation (section 4, 6.) encompasses the entire
terrestrial biosphere and its interaction with the atmosphere. It also addresses
the land use-dependent sink/source role of the biosphere through land cover
and land use products at appropriate spatial scales (section 4.2), thus providing
the framework for ecosystem-specific carbon estimates.
- A well-established need exists for information on the biosphere to
support sustainable development and resource management. Knowledge
of the carbon cycle, especially terrestrial productivity, has long been vital
to manage the biospheric resources upon which human societies depend. Appropriate
management is particularly important for countries whose economic and social
structures depend on production or subsistence agriculture. This motivation
becomes stronger as a large and increasing portion of the net primary production
is employed in the economic sphere (~ 40%; Vitousek et al., 1986), and is
further strengthened by continuing concerns about the long-term sustainability
of managed terrestrial ecosystems in the face of threats from salinity, soil
impoverishment and erosion.
Terrestrial carbon information is thus important from both public and private
enterprise perspectives, but with different emphases. From the public perspective,
governments are seeking policy instruments (either administrative or financial)
to improve land use and land management practice, reduce or reverse trends
towards the degradation of natural resources, and lessen the impact of natural
disasters such as drought. The design of these instruments depends on reliable,
detailed observations and predictions about the linked cycles of carbon, water
and nutrients upon which human use of the terrestrial biosphere depends. From
the perspective of private enterprise, information is typically needed at
a detailed and local level (for instance to manage a project for maximum productivity
and minimum leakage of contaminants or to support carbon trading). However,
larger-area information is also necessary to interpret local information and
use it in strategic planning. The importance of the interplay between public
and private institutions is clearly evident in the post-Kyoto developments,
with financial implications for the management and trading of terrestrial
carbon stocks.
- Improved knowledge of the carbon cycle, its variability, and its
likely future evolution is essential. There are large uncertainties
in the magnitudes and locations of carbon fluxes between the land, oceans
and the atmosphere. Current observations indicate that on average, 55% of
the released fossil fuel emissions accumulates in the atmosphere, and that
the carbon removed from the atmosphere is roughly partitioned equally between
oceanic and (mostly northern hemisphere) terrestrial systems. Also, land sinks
are more variable from year to year, in response to climatic as well as human
factors.
We presently lack the understanding and observations needed to close the annual
carbon budget at the global level. Furthermore, it is not possible to unambiguously
determine the spatial (geopolitical) distribution of carbon sinks, and previous
attempts to do so have suffered from an inadequate data base. Remedial programs
are being established in some regions; while these are important steps, they
cannot take the place of a co-ordinated global observing system. Based on
recent international research activities, it is evident that further progress
in our understanding of the global carbon cycle and its likely future evolution
depends on improved observations of the terrestrial carbon processes. For
example, in a special issue reporting results of an IGBP model intercomparison,
Cramer and Field (1999, p. iv) stated "...At the heart of these (efforts)
are enhanced experimental and monitoring systems (flux measurements, satellite
sensors, field and laboratory experiments, global data archives) which are
being identified by every single paper in this collection as being important
for better parameterisation of terrestrial biosphere models". Improvements
in models of the carbon cycle are essential for better projections regarding
its behaviour, a critical pre-requisite for future policy discussions and
measures. Conversely, improved understanding of the carbon cycle and the resulting
models will facilitate increases in the efficiency and effectiveness of the
observing systems and reporting procedures.
In addition,
- Capability to observe key components of the carbon cycle and its
dynamics has been established. The capabilities for making atmospheric,
ocean, and terrestrial carbon cycle observations have grown dramatically over
the last 20 years. Global and regional atmospheric trace gas concentration
measurement programs have been operating for many years, and the quantity
and quality of measurements has been steadily improving. In the terrestrial
domain, similar advances in satellite remote sensing have led to global and
regional products of land cover, fire, and measures of vegetation productivity.
National and regional terrestrial networks are working through GTOS and FLUXNET
to achieve consistent world-wide coverage. In parallel, numerical models of
combined atmosphere-ocean-land system have advanced rapidly, keeping pace
with the increasing speed and capacity of super-computing technology. Effective
use and further improvements of these models directly depend on systematic
global observations.
