June 19, 2003 — Carbon is the backbone of life on Earth, from the food that sustains us to the energy that fuels the world economies. In the form of carbon dioxide (CO₂) and methane (CH₄) in the atmosphere, it is also an important regulator of the Earth's climate as a major contributor to the planetary greenhouse effect. A small active fraction of the Earth's large carbon reservoirs exchanges naturally between the ocean, atmosphere and land. While the climate is directly affected by atmospheric concentrations of greenhouse gases, we must also understand how carbon cycles among these active reservoirs if we hope to be able to predict future atmospheric greenhouse gas concentrations accurately.

CO₂ and CH₄ concentrations have been increasing in the atmosphere since 1850 and are now higher than they have been for more than 400,000 years, primarily as a result of human use of fossil fuels and land clearing. Of the total emissions to the atmosphere, about half of the carbon emitted to the atmosphere (CO₂ and CH₄) is taken up by the oceans (and land). Specifically, the ocean (and land) is a sink for CO₂, while CH₄ is largely oxidized in the atmosphere (this explains why CO₂ has a relatively longer atmospheric lifetime compared to CH₄). Quantifying and reconciling these sinks with the remaining concentrations in the atmosphere has been and remains a major challenge, although recent advances have been made in understanding the continental U.S. land sink through NOAA-supported research.

A complete understanding of all the processes involved in the carbon cycle is still lacking, especially on land. Natural sources and sinks in the land and ocean are highly variable (in some years the sinks balance almost all emissions. In others they are effectively zero). Because we do not yet fully understand the direct causes of this variability, it is difficult to produce reliable forecasts of how they will change in the future. The coupled dynamics of carbon in the land, ocean and atmosphere could have a dramatic impact on future atmospheric CO₂, and therefore climate. (Click NOAA image below right for larger view of the Global Carbon Cycle).

Carbon Cycle Research
Recognizing the integrated nature of the carbon cycle, six federal agencies (Department of Energy, NASA, National Science Foundation, NOAA, U.S. Department of Agriculture, and U.S. Geological Survey) are coordinating their individual carbon cycle research programs to
address common research goals outlined in a U.S. Carbon Cycle Science Plan.

NOAA's Carbon Cycle Research
The main objective for the NOAA Global Carbon Cycle research program is to improve the ability to predict the fate of anthropogenic (man-made) CO₂ and future atmospheric CO₂ concentrations using a combination of global observations, process-oriented field studies and modeling. There are three major goals:

• Quantifying spatial patterns and variability of carbon sources and sinks at global to regional scales;
• Documenting the fate of anthropogenic CO₂ in the atmosphere and oceans; and
• Improving future climate predictions by incorporating a dynamic understanding of the carbon cycle into models.

A majority of NOAA's carbon cycle research is conducted by the following NOAA Research Laboratories:

• The Ocean Chemistry Division at the NOAA Atlantic Oceanographic and Meteorological Laboratory assess the ocean's role in controlling the exchange of CO₂ across the air-sea interface and its eventual penetration into the water masses of the deep ocean.
• The Carbon Cycle Greenhouse Gases group at the NOAA Climate Monitoring and Diagnostics Laboratory makes ongoing discrete measurements from land and sea surface sites and aircraft, and continuous measurements from baseline observatories and tall towers. These measurements document the spatial and temporal distributions of carbon-cycle gases and provide essential constraints to the understanding of the global carbon cycle.
• The GCC CO₂ Program at the NOAA Pacific Marine Environmental Laboratory in Seattle,
  Wash., conducts research on the sources and sinks of carbon dioxide in the oceans.
  Atmospheric and oceanic carbon dioxide data are collected on cruises onboard NOAA
  vessels and from the TAO moorings. Modeling studies employing these data enhance the understanding of the ocean's role in the global carbon cycle and the important feedback
  mechanisms that will affect future climate changes.
• The Earth System Applications Group at the NOAA Geophysical Fluid Dynamics
  Laboratory at Princeton, in close collaboration with close collaboration with
  the NOAA-funded Carbon Modeling Consortium at Princeton University form
  one of the leading centers for modeling and synthesizing data on the
  carbon cycle. Scientists within the group are developing models of
  carbon cycling in both the ocean and land biosphere. The output of these
  models is being closely compared with the data gathered by AOML, PMEL,
  and CMDL. Atmospheric and oceanic transport models under development at GFDL are
  also being used to establish the links between changing concentrations
  of CO₂ in both the atmosphere and ocean and the fluxes between the atmosphere,
  ocean and land biosphere that give rise to these fluctuations.

Highlights of currently funded research

• NOAA Carbon Air Sampling Studies: The NOAA CMDL Cooperative Air Sampling Network and a global climatology based on ocean data are key tools to monitor CO₂concentrations in the global atmosphere and document sources and sinks for carbon. Several modeling groups use these data to calculate global sources and sinks at the broad continental scale. Research suggests that land masses in the Northern Hemisphere (North America, Eurasia) are a net sink for excess CO₂ in the atmosphere. However, quantifying this sink over continents is a major challenge because of the complex covarying signals of CO₂ exchange over the land. A major program combining field observations, modeling and data assimilation seeks to test and build the next generation of observational tools to quantify sources and sinks at regional scales over North America and adjacent ocean basins. This program is the first effort to be collaboratively managed by the Carbon Cycle Interagency Working Group. NOAA hopes to support this effort through atmospheric observations over the land and ocean, surface carbon measurements in adjacent ocean basins and innovative data assimilation and modeling techniques.
  
• NOAA Carbon Air-Sea Exchange Studies: NOAA also funds process research to improve the quality of observations and to be able to use data more accurately at global to regional scales. One example of this research is the NOAA GCC's focus on air-sea exchange, currently a major source of uncertainty in quantifying ocean uptake at regional scales. NOAA and NSF are supporting a coordinated field campaign (Gas Ex 2001) studying the complex physical, chemical and biological forcing functions of CO₂ air-sea exchange in the equatorial Pacific. Once the CO₂ enters the surface ocean, its fate is further dependent upon physics, chemistry and biology in the ocean interior. Quantifying ocean interior inventories of total dissolved CO₂ and the anthropogenic CO₂ is very difficult on a global scale. NOAA and NSF are coordinating a repeat ocean survey of some of the major survey lines sampled as part of the Joint Global Ocean Flux Study and the World Ocean Circulation Experiment. These interdisciplinary surveys will be jointly sponsored by the CLIVAR program (Climate Variability).
  
• NOAA Carbon Modeling: Finally, model development is required to project future concentrations of CO₂ in the atmosphere, to aid in planning optimal sampling networks and to narrow uncertainty in model disagreements, including the role of oceanic CO₂ uptake. NOAA will endeavor to reduce these uncertainties through the development of coupled models that evaluate carbon fluxes, identify key processes and predict future atmospheric CO₂ concentrations. GFDL is one of the leading U.S. centers for modeling and predicting climate change. Work done at GFDL in the 1990's suggested that climate change could greatly affect the uptake of carbon by the oceans, but that ocean biology
  might mitigate this change. The uncertainty in how much carbon the atmosphere
  and ocean will take up over the next century amounts to hundreds of gigatons
  of carbon. GFDL is currently engaged in a an intensive model development program. New atmospheric, oceanic, and sea ice models have already been coded and coupled together and new carbon cycle models in the land and ocean are currently being developed and tested. These models will assist in designing operational observational systems, and bring dynamic understanding of the carbon cycle to be incorporated into improved climate forecasting products.

The President's Climate Change Research Initiative places emphasis on enhanced carbon sequestration (either through enhancement of biospheric carbon storage or through engineering solutions to capture carbon and store it in repositories, such as the deep ocean and geologic formations) as a near-term policy option to slow the rise in atmospheric CO₂ and provide more time to develop a wider range of viable mitigation options. Current interest in carbon sequestration centers on land management practices that enhance the storage of carbon in soils and biomass, fertilization of the ocean via iron inputs that enhance biological uptake of carbon, and direct CO₂ injection into the deep sea or geological features. However, uncertainties remain about how much additional carbon storage can be achieved, the efficacy and longevity of carbon sequestration approaches, whether they will lead to unintended environmental consequences, and just how vulnerable the global carbon cycle is to such manipulations. Despite these uncertainties and limited scientific information to evaluate the full range of impacts of these various carbon management strategies, NOAA's carbon cycle research is (and will continue to be) at the forefront of this issue.

Relevant Web Sites
Global Carbon Cycle (GCC) program

Global Carbon Cycle Themes

NOAA CLIMATE AND GLOBAL CHANGE GLOBAL CARBON CYCLE PROGRAM (GCC)
FY2004 Information Sheet

NOAA’s CLIMATE ACTIVITIES

THE CONTRIBUTION OF NOAA BUOYS TO A GLOBAL OCEAN OBSERVING SYSTEM:
BENEFITS TO CLIMATE PREDICTION AND RESEARCH

U.S. Carbon Cycle Science Plan

Carbon Cycle Interagency Working Group

Climate Change Research Initiative

AOML CO₂ Group

CMDL Carbon Cycle Greenhouse Gases (CCGG)

PMEL Global Carbon Cycle Program

NOAA Tropical Atmosphere Ocean Project

NOAA Ocean and Atmospheric Research

Climate Change Research Initiative

A Large-Scale CO2 Observing Plan: In Situ Oceans and Atmosphere

Autonomous Strategies for a Global Carbon Cycle Monitoring System

Air-Sea Gas Transfer Velocity: Its Dependence on Small-Scale Surface Waves and Surface Films

Oceanic CO2 Uptake Rates Determined from an Ocean-wide 13C/12C-DIC Data Set

Development of a Global Carbon System Model

Air-Sea Carbon Dioxide Fluxes and Surface Physical Processes

Measurements of Variations in Atmospheric O2/N2 and Ar/N2 Ratios and CO2 Concentrations in Relation to the Carbon Cycle and Climate

SURFACE ENERGY AND CARBON FLUX MEASUREMENTS SYSTEMS FOR REAL-TIME ASSESSMENT OF LAND SURFACE MODELS

CO2 Budget and Rectification Airborne Study - North America (COBRA-NA)

Atmospheric CO2 Inversion Intercomparison Project (Trans Com)

Transport and Storage of Carbon in the Pacific Ocean: Estimates from Inverse Models

2003 American Meteorological Society Conference: "The Need for a Global Observing System."
Vice Admiral (Ret.) Conrad C. Lautenbacher Jr., U.S. Navy Undersecretary of Commerce for Oceans & Atmosphere and NOAA Administrator. Long Beach, Calif. February 11, 2003

WRITTEN STATEMENT ON THE NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION'S FY 2003 BUDGET BY THE UNDER SECRETARY OF COMMERCE FOR OCEANS AND ATMOSPHERE CONRAD C. LAUTENBACHER, JR.
VICE ADMIRAL, U.S. NAVY (RET.) FOR THE SENATE COMMITTEE ON COMMERCE, SCIENCE AND TRANSPORTATION. MAY 1, 2002

Climate Observations and Services: Carbon Cycle Program. NOAA FY 2002

NOAA Climate and Global Change Program, Program Announcement; Global Carbon Cycle Element, FY 2002

PROGRAM ANNOUNCEMENT: National Oceanic and Atmospheric Administration Climate and Global Change Program. FY2002 Program Description and Timetable

Media Contact:
Jana Goldman, NOAA Research, (301) 713-2483