Nova projects a pie chart onto the roof wall. "NASA measured where the Sun's energy goes," she says.
"One hundred units arrive at the top of the atmosphere. Where do they end up?"
Rocket studies the slices. "A big slice bounces straight back to space. Clouds, snow, bright sand."
Raven points at the largest slice. "And the biggest slice reaches the ground. What do you notice about the sizes?"
"The ground gets about twice what the air gets," Rocket says. "So the ground does most of the heating."
"Which is exactly what you felt on Monday," Nova says. "Warm tiles, then warm air above them."
Raven starts copying the numbers into the log.
NASA's Earth Observatory describes Earth's energy budget: the balance between sunlight coming in and energy going back out.
On average, 340 watts per square meter of solar energy arrives at the top of the atmosphere.
The table below reproduces NASA's shares of that incoming sunlight.
| What happens to incoming sunlight | Share |
|---|---|
| Reflected back to space by clouds, particles and bright surfaces | About 29 percent |
| Absorbed in the atmosphere by water vapor, dust and ozone | About 23 percent |
| Passes through and is absorbed by the surface | About 48 percent |
Adding the two absorbed shares, about 71 percent of incoming solar energy is absorbed by the Earth system.
NASA notes that most solar heating happens at the surface, while most cooling to space happens from the atmosphere.
The Earth does not keep heating up, because the surface and the atmosphere radiate heat back to space.
A good data reader checks that the parts add up. Reflected plus absorbed should equal all the incoming sunlight.
29 plus 23 plus 48 makes 100. The budget balances.
Notice how the budget connects to Monday. The surface absorbs the most, warms, and then warms the air by conduction and convection.
Careful data work. Tomorrow you take uneven heating to the beach, and to your own area.