Big Questions for Terra

Terra (formerly EOS AM-1) is the flagship satellite of NASA's Earth observing systems. Terra is the first EOS (Earth Observing System) platform and provides global data on the state of the atmosphere, land, and oceans, as well as their interactions with solar radiation and with one another. This mission is part of SMD's Earth Systematic Missions program.

How is the global earth system changing?

Earth is currently in a period of warming. Over the last century, Earth's average temperature rose about 1.1°F (0.6°C). In the last two decades, the rate of our world's warming accelerated and scientists predict that the globe will continue to warm over the course of the 21st century. Is this warming trend a reason for concern? After all, our world has witnessed extreme warm periods before, such as during the time of the dinosaurs. Earth has also seen numerous ice ages on roughly 11,000-year cycles for at least the last million years. So, change is perhaps the only constant in Earth's 4.5-billion-year history.

How does the earth system respond to natural and human-induced changes?

Climate scientists have been monitoring Earth's energy budget since the 1978 launch of NASA's Nimbus-7 satellite. That mission carried a new instrument into space called the Earth Radiation Budget Experiment (or ERBE), designed to measure all of the energy leaving through the top of Earth's atmosphere. All of the incoming sunlight minus all of the reflected sunlight and emitted heat is our world's energy budget. The second law of thermodynamics compels Earth's climate system to seek equilibrium so that, over the course of a year the amount of energy received equals the amount of energy lost to space. So typically the global energy budget is in balance.

How will the Earth system change in the future?

As the world consumes ever more fossil fuel energy, greenhouse gas concentrations will continue to rise and Earth's average temperature will rise with them. The Intergovernmental Panel on Climate Change (or IPCC) estimates that Earth's average surface temperature could rise between 2°C and 6°C by the end of the 21st century.