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Striking a Solar Balance
Narrator: Planet Earth is an oasis of life. But without the Sun, our home planet would be little more than a frozen rock stranded in space.
Narrator: The Sun is a powerful, blazing star. It radiates huge amounts of electromagnetic energy in all directions. Earth is only one small recipient of the Sun’s energy; the Sun’s rays extend far out into the solar system, illuminating all the other planets.
Narrator: The Sun warms the Earth and makes life possible here. Its energy also generates clouds, cleans our water, and drives ocean currents, thunderstorms, and hurricanes.
Narrator: For three decades, NASA scientists have investigated the unique relationship between the Sun and the Earth. They study the solar power arriving at Earth, and they examine how it breaks down into different wavelengths. 30% of incoming solar power is reflected back into space by things like clouds, aerosols, ice, and snow. The remaining 70% is absorbed by the land, ocean, and atmosphere, and this solar power is what drives the climate system. The Earth’s energy budget is a delicate balance between incoming solar and outgoing thermal energy.
Bob Cahalan: It’s the balance between those two forms of energy that determines the temperature of the planet. Our energy budget is a little bit out of balance now, and that’s due to the carbon dioxide & other greenhouse gases in the atmosphere.
Narrator: As humans burn fossil fuels, greenhouse gases accumulate in the atmosphere and block Earth’s outgoing heat. The resulting imbalance will cause the Earth to heat up over the next century, accelerating the melting of polar ice caps, causing sea levels to rise, and creating more violent global weather patterns.
Narrator: Humans affect Earth’s climate internally, and the Sun is the primary external influence. Sunspots and solar weather cause incoming solar power to vary, and long-term fluctuations in the solar cycle can impact Earth’s climate.
Narrator: As the Earth warms, scientists strive to better understand the Sun’s direct and indirect effects on the Earth. For the past three decades, a suite of NASA satellites has provided scientists with measurements of total solar irradiance. This uninterrupted 30-year record of incoming solar power is a critical tool for examining Earth’s vital relationship with the Sun.
Narrator: The Total Irradiance Monitor, or TIM instrument, was launched in 2003 as part of NASA’s SORCE mission. TIM measures total solar irradiance with state of the art accuracy, and has been rebuilt as part of NASA’s upcoming Glory mission. Scheduled to launch in 2009, Glory will also collect data on aerosols, one of the least understood components of the climate puzzle. As our home planet changes in unprecedented ways, researchers will continue to rely on NASA missions to illuminate their understanding of the Earth and the Sun.
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