Which factor best accounts for seasonal changes in weather at a particular location on Earth?

• A. Tilt of earth's rotational axis
• B. Distance from the Sun
• C. Ocean currents
• D. Atmospheric pressure

Answer: (A)

Seasonal changes are driven by the tilt of the Earth's axis. The axis is tilted about 23.5 degrees relative to its orbit around the Sun, so during the year different hemispheres are tilted toward or away from the Sun. That changes both the Sun’s angle in the sky and the length of daylight. In summer, the Sun climbs higher, days are longer, and sunlight is more direct, warming surface temperatures. In winter, the Sun stays lower in the sky, days are shorter, and sunlight is less direct, leading to cooler temperatures. The distance from the Sun varies a bit, but that variation is small compared to the effect of tilt, and doesn’t account for the seasonal pattern. Ocean currents and atmospheric pressure influence weather within each season, but they don’t cause the seasonal cycle itself.