Earth system science
Viewing the Earth with a systems approach allows scientists to examine a dynamic and complex collection of parts that contribute to our understanding of the interactions within and between the atmosphere, biosphere, hydrosphere, and lithosphere. These parts, the "spheres" themselves, encompass the physical, chemical, and biological processes that have occurred on our planet through time. Although our planet can be viewed in the much larger context of the solar system and galaxy, sometimes termed the exosphere, this page will not address the impact of asteroids and comets on Earth.
Discussions around Earth system science began in 1983 when the NASA Advisory Council established the Earth System Sciences Committee, which published their revolutionary report  in 1986. The report established that the goal of Earth system science "is to obtain a scientific understanding of the entire Earth system on a global scale by describing how its component parts and their interactions have evolved, how they function, and how they may be expected to continue to evolve on all timescales" (p. 4). Interestingly, although a motivation for the Earth system science view was the growing impact of humans on the Earth system and need to provide solutions, the study of the social drivers and their consequences for the changes that were occurring was not incorporated in these early discussions.
Basic Elements of the Earth system
Each sphere is a component of the Earth system, and each component is made up of elements (a grasshopper is an element of the biosphere, a metamorphic rock is an element of the lithosphere, etc.). At any moment in time, all matter and energy on Earth is part of one or more of these spheres, and across time, all of Earth's matter cycles through two or more of these spheres.
Earth's atmosphere, nicknamed "the gaseous layer," surrounds the planet and is composed primarily of nitrogen, oxygen, argon, and carbon dioxide. The atmosphere is divided in to five separate layers defined by changes in temperature that happen with increasing altitude. The lower layer of the atmosphere, termed the troposphere, includes clouds, water vapor, solid particles such as dust and pollen, and is the layer of all weather on Earth. Atmospheric researchers are very interested in investigating how atmospheric processes determine patterns of surface precipitation, temperature, and other aspects of surface climate.
The biosphere, or "living sphere," includes living organisms and their activities, such as photosynthesis, respiration, and decay. The biosphere includes plants, animals, and all ecosystems, from the highest mountains to the ocean floor. Because life can exist in the air and in the water, the biosphere will overlap with the other existing spheres. Humans and human activity, such as burning forests or fossil fuels, is sometimes noted as a subsphere termed the anthrosphere. Planet Earth was designated by some as Biosphere 1 after the completion of Biosphere 2, a self-contained dome-like structure with humans living with five biomes and an agricultural area in the Arizona desert.
The "water sphere" includes all bodies of fresh and frozen water on the planet, from lakes to rivers to the oceans. The hydrosphere covers approximately 70% of the surface of the Earth. The hydrosphere also includes water below the surface in groudwater systems, and water vapor (clouds and fog) located in the atmosphere. When water is in its solid form (ice or snow), it is sometimes referred to as the cryosphere.
The lithosphere is the solid, rigid, "rocky" outermost layer of Earth that includes the crust and uppermost mantle materials. In an Earth system science context, the lithosphere includes tectonics, earthquakes, volcanism, and erosion and sedimentation. Sometimes called the "geosphere," scientists will add the outermost soil layer to this classification or place soil in a subsphere named the pedosphere.
Each of the spheres has events that are contained within an individual sphere and that cut across spheres. An event in one sphere may cause an action or reaction that may then have an effect in one or more sphere. Studying the interactions within and between spheres is a critical part of Earth system science.
- Earth System Science Committee (1986). Earth System Science Overview: A Program For Global Change. Washington DC, NASA.
- Mooney et al., 2013. Evolution of natural and social science interactions in global change research programs. Proceedings of the National Academy of Sciences, v. 110, p. 3665-3672.
- NASA Science - Earth, Atmospheric Composition.
- Egger, A., The Composition of Earth's Atmosphere. Visionlearning, Vol. EAS (5), 2003.
Other closely related articles in this wiki include:
- Earth system science in a nutshell (http://serc.carleton.edu/introgeo/earthsystem/nutshell/index.html) - background article designed for middle school to university faculty to explain using a systems approach in teaching. A more detailed description of each system (air, water, land, life, the human dimension) is provided online.
- Earth system science (http://www.cotf.edu/ete/ESS/ESSmain.html) - from NASA Classroom of the Future, additional background information suitable for middle school to university faculty and students
- Earth System Science EarthLabs for Educators and Policy Makers (http://serc.carleton.edu/earthlabs/climate/index.html) - hosted at SERC, written as high school laboratory modules that can be scaled up or down to appropriate grade levels
- The Encyclopedia of Earth - atmosphere and biosphere,
- On the National Geographic Education site: atmosphere, biosphere, hydrosphere, lithosphere