What is the primary source of energy for Earth's weather and climate system?

• A. The Moon
• B. The Sun
• C. Earth's core
• D. Geothermal energy

Answer: (B)

The main thing this question is testing is what powers the weather and climate system. The Sun is the primary energy source. Its radiant energy heats Earth's surface and the air above it. Because the Sun shines at different angles and different surfaces absorb heat differently, there are temperature differences from place to place and over time. These differences set air in motion: warm air rises, cooler air sinks, and winds develop to move heat around.

That energy also fuels the water cycle. Sunlight causes surface water to evaporate, forming water vapor. When that vapor rises and cools, it condenses into clouds and eventually falls as rain or snow. The release of latent heat during condensation adds energy that drives storms and helps shape weather patterns.

Earth’s energy balance is kept by the Sun’s input and energy radiated back to space, which keeps the climate relatively stable on long timescales. Other sources, like geothermal energy from Earth’s interior or effects from the Moon, contribute very little to the overall energy driving weather and climate. Geothermal heat is a tiny part of the global energy budget, and the Moon does not provide energy for weather—its influence is mostly through tides, not atmospheric heating.

So, solar energy is the best answer because it directly powers the heating, circulation, and moisture processes that produce weather and shape climate.