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No single scientific discipline or research method can address the full range of questions related to global change. Physical, geological, chemical, biological, ecological, social, behavioral, and economic processes interact with each other in various ways—with changes to one system inevitably affecting many others.

Understanding the full picture of complex interactions requires diverse expertise, capabilities, and scientific approaches—ranging from controlled laboratory experimentation and field research campaigns, to modeling of complex multivariate systems and analyzing data trends across vast scales of time and space.

It is the job of scientists to stitch together insights that emerge from these various lines of inquiry, identify gaps or weaknesses in collective understanding, and seek new ways to address them. This iterative process is what ultimately leads to discovery and progress.

Two of the main ways in which the agencies that make up the U.S. Global Change Research Program (USGCRP) study climate and global change, are making observations and applying computer models.

Make Observations

The Earth System

Observations across all of Earth’s domains – atmospheric, oceanic, and terrestrial – improve understanding of how Earth systems operate and how they respond to human activities. Satellite observations of changes to the Greenland ice sheet, for example, help scientists document the effects of human-induced global change on the high-latitude environment and potential implications for sea level rise.

By definition, observations reveal processes and impacts that have already occurred, or are ongoing. But they also underpin our ability to predict future behavior. For example, observations are used to test and evaluate models that predict future long-term global change, and to inform short-term weather forecasts, among other critical tasks.

USGCRP works to integrate observations of all essential Earth system components and processes in order to better understand the Earth system and to more effectively manage the risks of global change. Such integration is essential for developing theories and explanations of the causes and consequences of global change. Read more about how we make observations.

Develop and Apply Models

The Earth System

Models help scientists understand the behavior of Earth systems that sometimes interact in surprising ways, like links between aerosols, ocean temperatures, and weather patterns. Models also allow scientists to predict the future behavior of systems, including how they will respond to human influences (such as increases in greenhouse gases and large-scale land-use change) over time.

The earliest climate models incorporated atmosphere and land-surface components. Over time, additional components that we now know are critical pieces of the climate system—such as oceans and sea ice—began to be incorporated.

More recently, climate models have been expanded to include detailed representations of ice sheets, atmospheric chemistry, biogeochemical cycles, and more. Scientists are continuously testing, evaluating, and improving these components so that models simulate Earth systems as accurately as possible. Read more about how we develop and apply models.

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