Question

Explain why increasing concentrations of \(\mathrm{CO}_{2}\) in the atmosphere affect the quantity of energy leaving Earth but do not affect the quantity entering from the Sun.

Short answer

Increasing concentrations of \(\mathrm{CO}_2\) in the atmosphere affect the quantity of energy leaving Earth, as they absorb and trap long-wave infrared radiation emitted by the Earth's surface, thereby slowing down the rate at which energy is radiated back to space. However, they do not affect the quantity of energy entering from the Sun because greenhouse gases like \(\mathrm{CO}_2\) do not absorb incoming shortwave radiation, which is the dominant form of energy received from the Sun.

Step-by-step solution

Understand the Role of CO2 in the Atmosphere

Carbon dioxide (\(\mathrm{CO}_2\)) is a greenhouse gas present in the Earth's atmosphere. The primary role of greenhouse gases is to absorb and emit infrared radiation, which then gets trapped in the atmosphere. This process is responsible for maintaining the Earth's temperature and is known as the greenhouse effect.

The Greenhouse Effect

The greenhouse effect occurs due to the interaction of Earth's atmosphere with incoming solar radiation and outgoing radiation from the Earth's surface. The Earth absorbs energy from the Sun in the form of shortwave radiation (visible light, ultraviolet, and near-infrared), some of which gets reflected back to space. The Earth's surface then radiates long-wave infrared energy back to the atmosphere, where greenhouse gases like \(\mathrm{CO}_2\) absorb this energy, trapping it within the atmosphere, and warming the Earth.

The Energy Balance

The Earth's energy balance is determined by the balance between incoming solar radiation and outgoing radiation from the Earth's surface. As greenhouse gases like \(\mathrm{CO}_2\) absorb long-wave infrared radiation, they increase the amount of energy retained in the Earth's atmosphere. This process affects the quantity of energy leaving Earth, as it slows down the rate at which energy is radiated back to space.

Effect on Incoming Solar Radiation

Increases in atmospheric \(\mathrm{CO}_2\) concentrations do not affect the quantity of energy entering Earth from the Sun because the incoming energy is dominantly in the form of shortwave radiation, which greenhouse gases do not absorb. The greenhouse effect mainly influences long-wave infrared radiation, which is emitted by the Earth's surface after absorbing solar energy.

Conclusion

In conclusion, increasing concentrations of \(\mathrm{CO}_2\) in the atmosphere affect the quantity of energy leaving Earth by trapping more long-wave infrared radiation emitted by the Earth's surface, but they do not affect the quantity of solar energy entering Earth from the Sun. This is because greenhouse gases like \(\mathrm{CO}_2\) do not absorb shortwave radiation, which is the dominant form of energy entering Earth from the Sun.