Carbon is a fundamental part of the Earth system. It is one of the primary building blocks of all organic matter on Earth and a key element in setting Earth’s temperature. Carbon moves from the atmosphere to the land, ocean, and life through biological, chemical, geological and physical processes in a cycle called the carbon cycle. Because some carbon gases are greenhouse gases, changes in the carbon cycle that put more carbon in the atmosphere also warm Earth’s climate.
On the short time scale, the carbon cycle is most visible in life. Plants on land and in the ocean convert carbon dioxide to biomass (like leaves and stems) through photosynthesis. The carbon returns to the atmosphere when the plants decay, are eaten and digested by animals, or burn in fires. Because plants and animals are an integral part of the carbon cycle, the carbon cycle is closely connected to ecosystems. As ecosystems change under a changing climate, the carbon cycle will also change. For example, plants may bloom earlier in the year and grow for more months (assuming sufficient water is present) as the growing season gets longer, altering the food supply for animals in the ecosystem. If more plants grow, they will take more carbon out of the atmosphere and cool temperatures. If, on the other hand, warming slows plant growth, habitats will shift and more carbon will go into the atmosphere where it can cause additional warming.
Terra and the Carbon Cycle
Terra’s five instruments provide measurements of plant (vegetation) composition, structure, extent, and change. All four measurements are necessary to estimate how much carbon plants take up as they grow, and how much is being released to the atmosphere over time. Terra also measures concentrations of carbon monoxide in the atmosphere. Since Terra measurements begin in 2000, they provide a record of the rate and extent of change for more than a decade.
MODIS measures chlorophyll concentrations and fluorescence at the ocean surface to assess the concentration and health of photosynthesizing organisms like phytoplankton. Such measurements indicate how much carbon is taken up by ocean biology. MODIS also measures particulate organic carbon and particulate inorganic carbon, which can be used to gauge how much carbon the ocean exchanges with the atmosphere directly. See The Ocean’s Carbon Balance on the Earth Observatory.
MISR collects data on the general height and structure of broad areas of vegetation (the canopy structure), the area covered by photosynthesizing leaves, and the amount of energy absorbed by leaves. Such measurements provide insight into carbon flux. MODIS collects a variety of measurements that indicate how much plants are growing, including vegetation indices, leaf area index, primary productivity, and evapotranspiration. See Measuring Vegetation on the Earth Observatory.
Land cover change
The MODIS land cover product indicates what type of vegetation is growing (forest, grassland, etc.) in a given location. Disturbance products, including the burned area product, show how land cover changes through deforestation or reforestation, agriculture, fire, urbanization, and so forth. ASTER’s 15 meter resolution imagery can be used to assess land cover change on a local scale, particularly as it relates to events like fires, floods, landslides, or volcanic eruptions. Although CERES does not directly collect data on carbon; it does collect data on energy flux, in relation to energy balance, that takes place in vegetation and land surface.
MOPITT measures carbon monoxide in the atmosphere. While carbon monoxide (CO) is not itself a greenhouse gas, CO is chemically linked with methane, ozone, and carbon dioxide, and therefore impacts both climate and air quality. Primary sources of CO include fossil-fuel burning, biomass burning and methane oxidation. MOPITT measurements of CO concentrations in the troposphere are based on observations made with a suite of gas correlation radiometers operating in two CO-sensitive spectral bands. MOPITT CO products are used to study the movement of pollution in the atmosphere, to quantify CO emissions and to support air quality forecasts.