For over four decades, NASA has been unraveling the intricate dance of energy between the Sun and Earth, but the story is far from over.
Imagine trying to balance a scale where one side holds the relentless energy of the Sun, and the other, the delicate equilibrium of our planet’s climate. This is the essence of Earth’s energy budget, a concept that has captivated scientists since the late 19th century. But it wasn’t until 1958, with the launch of Explorer 1—America’s first satellite—that we began to measure this cosmic interplay. Though Explorer 1’s mission ended in 1958, its legacy sparked a revolution in Earth observation. By 1975, NASA’s Nimbus instrument took the stage, offering the first global glimpse of solar radiation flowing in and out of our atmosphere. This breakthrough not only refined early climate models but also paved the way for the Earth Radiation Budget Experiment (ERBE).
And this is the part most people miss: Determining the ‘top of the atmosphere’ wasn’t just a technical detail—it was a full-day debate for the ERBE team in the 1970s. After much deliberation, they settled on a boundary roughly 18 miles (30 kilometers) above Earth’s surface. This precision laid the foundation for ERBE’s launch in 1984 aboard the Earth Radiation Budget Satellite (ERBS), carried by the space shuttle Challenger. Bruce Barkstrom, a retired ERBE scientist, recalls the emotional launch: ‘The shuttle’s exhaust lit up the overcast sky, and minutes later, the sun reflected off the exhaust, creating a second burst of light. It’s hard to describe without feeling moved.’
For a decade, ERBE provided critical data on how the Sun’s energy interacts with clouds and Earth, revealing that clouds play a cooling role in our climate. This discovery fueled the development of the Clouds and the Earth’s Radiant Energy System (CERES), which launched in 1997. CERES instruments, described by Principal Investigator Kory Priestley as ‘small, elegant, and NASA’s most accurate radiometry,’ have since expanded our understanding of solar energy reflection, planetary heat emission, and cloud dynamics. The final CERES instrument joined the Joint Polar Satellite System (JPSS)-1 in 2017, continuing this legacy.
But here’s where it gets controversial: Despite 42 years of observation, our grasp of Earth’s energy budget remains incomplete. ‘You’re always at the mercy of somebody discovering something new,’ Barkstrom notes. This ever-evolving understanding underscores the importance of missions like NASA’s Total and Spectral Solar Irradiance Sensor (TSIS)-1, which measures the Sun’s energy input from the International Space Station. Since 1978, such measurements have been vital for studying solar variability’s impact on Earth’s ozone, atmosphere, and ecosystems.
So, why does this matter? Accurate, long-term data on Earth’s energy budget improves climate models, enabling better seasonal and long-term forecasts. These insights guide industries and policymakers in preparing for the future. Yet, the science is far from settled. What if clouds’ role in climate cooling is more complex than we think? Or if solar variability has greater impacts than current models predict? These questions invite us to keep exploring, debating, and discovering. What’s your take? Do you think we’re close to fully understanding Earth’s energy budget, or is there still much to uncover? Share your thoughts below!
