
The difference between the sunlight the planet absorbs and the heat it radiates back, measured from satellites (CERES). Positive means the planet is gaining heat.The imbalance is small—about 0.5 to 1 watt per square meter—but over the whole planet, that adds up to an enormous amount of energy, roughly 20 times the world's total energy consumption. This excess heat does not stay in one place: about 90% of it goes into warming the ocean, with the rest melting ice, warming the atmosphere, and heating the land. Tracking EEI is therefore essential for understanding how fast sea levels will rise, how much heat stress the ocean will experience, and how quickly the atmosphere will warm. It also serves as a check on our understanding of the climate system: if models and observations disagree on EEI, something is missing from the models.
The concept of Earth's energy balance dates back to the 19th century, but precise satellite measurement of the imbalance became possible with the CERES instruments, which began flying in 1997 on the TRMM satellite and later on Terra and Aqua. The sustained record from these missions has provided the most accurate estimates of EEI.
EEI is measured directly from space using radiometers that detect the solar and thermal radiation at the top of the atmosphere. The Clouds and the Earth's Radiant Energy System (CERES) instruments on NASA satellites scan the entire planet, measuring the reflected sunlight and the outgoing infrared radiation. The difference between the absorbed solar radiation and the emitted thermal radiation gives the net energy flux. To get a reliable estimate, these satellite measurements must be carefully calibrated and averaged over months and years, because the imbalance is tiny compared to the huge flows of energy passing through the system.
EEI is used to monitor the rate of global warming, validate climate models, and estimate the ocean's heat uptake, which is critical for projecting sea-level rise and future climate scenarios.
The excess energy absorbed by Earth each year is equivalent to the energy of about four Hiroshima bombs detonated every second.






