Connected Earth systems, illustration. Like the human body, Earth comprises diverse processes and systems that interact with one another in complex ways. Scientists study these systems and their responses to natural and human-induced changes, using Earth-observing satellite and airborne missions to observe and understand the planet on global and regional scales. Measurements recorded include surface temperature, winds, water vapor, clouds, precipitation, soil moisture, ocean salinity, and other aspects of the environment. Global numerical models allow the study of component system interactions to show how the Earth functions as one integrated system.