What are Aerosols?

Changing Global Cloudiness

Why Isn't Earth Hot as an Oven?

Changing Global Land Surface

The Roles of the Ocean in Climate Change

About the Terra Spacecraft

Figure 1. Artist's rendering of the Terra spacecraft.

4.5-billion-year history is a study in change. Natural geological forces have been rearranging the surface features and climatic conditions of our planet since its beginning. Today, there is compelling scientific evidence that human activities have attained the magnitude of a geological force and are speeding up the rates of global changes. For example, carbon dioxide levels have risen 25 percent since the industrial revolution and about 40 percent of the world’s land surface has been transformed by humans. (Terra’s five main science objectives are discussed in detail in the fact sheets listed in the left-hand column of this page.)

Scientists don’t understand the cause-and-effect relationships among Earth's lands, oceans, and atmosphere well enough to predict what, if any, impacts these rapid changes will have on future climate conditions. Scientists need to make many measurements all over the world, over a long period of time, in order to assemble the information needed to construct accurate computer models that will enable them to forecast the causes and effects of climate change. The only feasible way to collect this information is through the use of space-based Earth “remote sensors” (instruments that can measure things like temperature from a distance). Consequently, NASA’s Earth Observing System has begun an international study of planet Earth that is comprised of three main components: 1) a series of satellites specially designed to study the complexities of global change; 2) an advanced computer network for processing, storing, and distributing data (called EOSDIS); and 3) teams of scientists all over the world who will study the data.

On February 24, 2000, Terra began collecting what will ultimately become a new, 15-year global data set on which to base scientific investigations about our complex home planet. Together with the entire fleet of EOS spacecraft, Terra is helping scientists unravel the mysteries of climate and environmental change. If you want to learn more about other EOS missions, visit the EOS Missions Page. If you want to learn about new EOS science results, visit the Earth Observatory.

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