The Earth System Print E-mail

Earth System Interactions

U.S. Carbon Cycle Science Program

The seemingly separate elements of Earth system science are in reality all connected across multiple dimensions and pathways. Some of the most important and challenging areas of future study will be located at the dynamic interfaces between components and processes - the ways in which one part of the Earth system influences the others.

Understanding global change is difficult because the Earth system is complex, with behavior that emerges as a result of many interactions on multiple scales among the atmosphere, ocean, ice sheets, land surface, and the biosphere.

People add to this complexity because they are a part of the Earth system. They not only influence but are influenced by Earth system changes. They can also consciously choose how to respond to these changes while considering and observing the implications of their response.

To advance scientific understanding of the changing Earth system, and to build a more integrated global change science program, the U.S. Global Change Program (USGCRP) must consider the interdependencies of Earth's different components and processes.

USGCRP Efforts

USGCRP aims to achieve a deeper, more fundamental understanding of the physical, chemical, biological, and human components of the Earth system, and the richness of behaviors that result from the interactions of these systems with each other. In order to to deepen the understanding of individual natural and human Earth system components and processes USGCRP works to:

  • Consider an expanded range of global change dimensions and their interaction with climate change
  • More fully integrate the biological and ecological sciences, and the social, behavioral, and economic sciences with physical climate science
  • More comprehensively explore the multiple space and timescales that characterize global change processes, including the role of natural climate variability and the importance of extremes
  • Investigate the complex, nonlinear behaviors in the Earth system and the tipping points that might be crossed as a result of global change

Please click on the buttons below for more information on the core efforts USGCRP is undertaking to improve our understanding of the Earth system.


For many systems and sectors, particularly at local scales and in the near-term, climate change is not the only important stressor. Effective responses to global change rarely involve climate change in isolation. In order to achieve a more comprehensive understanding of the complex, system-oriented phenomena that create global change, a more holistic view of the dimensions of global change is necessary.

In addition to climate change, global change has multiple linked and nested dimensions, including:

  • Land-use and land-cover change
  • Modification of the carbon, nitrogen, phosphorous, and sulfur cycles
  • Pollution
  • Loss of biodiversity and ecosystem functions and services
  • Alteration of hydrologic systems
  • Human population dynamics, including growth, migration, and demographic shifts

To advance Earth System understanding, USGCRP considers an expanded range of global change dimensions and their interaction with climate change. USGCRP research addresses not only the dynamical interactions among atmosphere, ocean, land, and ice, but also the interactions between these climate system processes and other key dimensions of global change, such as ecosystem dynamics, key biogeochemical cycles, and human alteration of the water cycle.

Greater integration of physical climate system research with the biological sciences (including but not limited to the biogeochemical and ecological sciences) is essential for advancing integrated Earth system science and the knowledge base for managing risk.

Global change research includes the range of interactions between the biosphere and climate dynamics, from the exchange of carbon dioxide among different terrestrial and oceanic reservoirs, to the cycling of water, to the impacts of the biosphere on the radiative properties of the Earth’s surface and atmosphere.

Processes at the population, species, community, and ecosystem levels are all critical for understanding the causes and consequences of global change. For example, a number of important ecosystem services (e.g., crop pollination) can only be understood through population- and community-level studies.

Gaps remain in critical areas ranging from Earth system tipping points to the decisions humans make on sustaining and managing natural systems under a changing climate and other global change pressures. Better coordination of the biological sciences with climate change research will provide the new knowledge and knowledge syntheses that will be required to inform decisions about managing the risks of global change.

Many of the critical questions related to understanding and responding to global change cannot be adequately addressed without substantial contributions from the social, behavioral, and economic sciences.

For example, population dynamics, natural resource consumption patterns, economic development, governance, and the development and adoption of new technologies underlie the human drivers of global change. Global change will affect death and migration rates, consumption of energy and other resources, and attitudes about the adoption of new technologies.

Similarly, the cognitive basis for decision making governs individual and societal responses to global change, and these actions occur within, and are constrained by, institutions, social networks, and political, economic, and cultural contexts. These, in turn, interact with public understanding of science and technology, as well as risk perception and communication.

Meeting this challenge requires expanding the engagement of the social, behavioral, and economic disciplines in global change science to achieve a deeper understanding of the vulnerabilities and responses to global change. To foster and integrate the contributions of multiple disciplines, USGCRP:

  • Uses the coordination mechanisms of the Program to enhance dialogue and collaboration between these communities
  • Leverages the expertise in agencies, or parts of agencies, that have not traditionally been part of USGCRP
  • Harnesses the enhanced capacity in social, behavioral, and economic sciences that is being developed and sustained under the auspices of the National Climate Assessment (NCA).

USGCRP established a Social Sciences Task Force to identify options, and provide recommendations, for accelerating this integration. Read more about the Social Sciences Task Force.

USGCRP is comprehensively exploring the multiple space and timescales that characterize global change processes, including the role of natural climate variability and the importance of extremes to better inform decisions in agriculture, water resources, disaster management, and many other societally critical sectors.

To better address scales, natural variability, and extremes, USGCRP conducts observations, and improved modeling of the Earth’s energy budget – at the top of the atmosphere, in melting ice, atmospheric convection, and other transformations of water, and in the ocean. The program also:

  • Focuses on finer spatial and temporal resolution in observations and modeling to link, for example, climate system processes with the dynamics of ecosystems and human communities
  • Integrates the aggregate effects of small-scale, short-term processes and behaviors (both human and natural) into the understanding of Earth system behaviors at the global scale
  • Focuses not just on long-term averages, but on the effects of global change on much shorter timescale phenomena such as the extremes discussed previously

The multiplicity of interconnections among different Earth system components, and among processes occurring at different scales, can lead to changes that are difficult to observe, measure, monitor, or model as they are starting to occur. Thus, anticipating these changes and responding effectively are more challenging.

Research on the properties of complex systems suggests that large, abrupt changes in the Earth system will become increasingly likely with increasing disturbance. Earth may approach new and as yet unidentified tipping points in its biological systems, the biogeochemical cycles that help regulate the concentrations of greenhouse gases in the atmosphere, ocean circulation patterns, and ice sheet stability. Such changes could occur so rapidly that they would challenge the ability of human and natural systems to adapt.

Current scientific understanding must be improved significantly before the above mentioned risks can be comprehensively assessed and used to inform risk management decisions and strategies. In response to this need, USGCRP places a high priority on research to understand rates, processes, mechanisms, and consequences of global change and the complex, nonlinear climatic, ecological, and social system dynamics leading to abrupt changes, thresholds, and tipping points.

Understanding past changes in temperature, precipitation, ocean chemistry, sea level, and sensitivity to changes in atmospheric carbon dioxide levels gained from studying the paleoclimatic record play a critical role in USGCRP's research. The long time series data provided by paleoclimatic records are invaluable for improving understanding of natural variability on decadal and longer timescales, and the sampling of climatic conditions from past centuries provides crucial tests of model performance.

In addition, the Program fosters significant advances in the understanding of the potential unintended consequences of actions taken in response to global change, as such actions themselves have the potential to upset natural balances in significant and potentially unexpected ways.