Between 35°N/North Pole and 35°S/South Pole, does outgoing radiation exceed incoming insolation?

• A. Outgoing radiation exceeds incoming insolation
• B. Incoming insolation exceeds outgoing radiation
• C. They are equal
• D. No energy transfer occurs

Answer: (A)

Latitudinal energy balance drives how much energy a region gains from the Sun versus how much it loses as heat to space. Beyond about 35° from the equator toward the poles, the Sun’s rays strike at a low angle and daylight is shorter for much of the year, so the average incoming solar energy is relatively small. The air and surface are also cooler, so the amount of infrared radiation they emit is lower. Yet, the rate at which they radiate energy to space still ends up exceeding the small amount of solar energy they receive over the year. In short, these high-latitude regions are net radiators, losing more energy to space than they gain from the Sun. This difference is balanced globally by energy transported from the tropics to the poles by atmosphere and oceans.