Question

Imagine that the composition of Earth's atmosphere was altered so that its ability to absorb visible and far infrared light was reversed. a. If you were outdoors when the Sun was at its highest point in the sky, how would the sky appear? b. Would there be an increase or decrease in Earth's average surface temperature?

Short answer

a. The sky would appear darker. b. There would be a decrease in Earth's average surface temperature.

Step-by-step solution

Understand the Scenario

Currently, Earth's atmosphere absorbs some infrared light but allows most of the visible light to pass through. In the altered scenario, it would absorb more visible light but let more infrared light escape.

Analyzing the Appearance of the Sky

When the Sun is at its highest point, the usual scattering of visible light makes the sky appear blue. If visible light is absorbed rather than scattered, the sky would appear significantly darker.

Analyzing Earth's Temperature

The absorption of visible light would mean less light reaches the surface, potentially cooling it during the day. Meanwhile, increased infrared emission would enhance cooling, leading to a general decrease in surface temperature.

Key concepts

Visible Light Absorption

Visible light is the part of the electromagnetic spectrum that our eyes can see. Currently, Earth's atmosphere allows most visible light to pass through it. This light gets scattered by air molecules, which is why we see a blue sky on a sunny day.
However, if the atmosphere absorbed more visible light instead of scattering it, things would change significantly:

• Less light would make it to the ground, leading to a darker environment during the day.
• The sky might seem less bright or darker because less light is scattered to reach our eyes.

This scenario helps us understand that visible light absorption dramatically affects how bright our surroundings are.

Infrared Light Emission

Infrared light is a type of electromagnetic radiation that is not visible to the human eye. It is primarily associated with heat. Our atmosphere absorbs much of the infrared light emitted from the Earth's surface, helping regulate temperature by trapping heat. In this scenario, if the atmosphere's properties were reversed to let more infrared light escape:

• The Earth's heat would be lost more quickly to space.
• This loss of heat would contribute to cooling the surface, especially during the nighttime.

Understanding infrared light emission is crucial in comprehending how Earth's natural greenhouse effect functions and how its alteration could impact our climate.

Surface Temperature Changes

The balance between light absorption and heat emission has a direct effect on Earth's surface temperature. If the atmosphere absorbed more visible light but emitted more infrared light:

• Less sunlight would reach and warm the Earth's surface during the day, slightly cooling it.
• The increased emission of infrared light would result in more heat escaping, further reducing temperatures.

This change hints at an overall decrease in temperature, demonstrating how atmospheric composition is vital for maintaining Earth's habitable conditions.

Sky Appearance Change

The appearance of the sky depends on how the atmosphere interacts with sunlight. Normally, visible light is scattered, giving us a blue sky. But what if the atmosphere absorbed more of this light?

• The sky could appear darker, as less light would scatter back to our eyes.
• Bright, sunny skies might become less frequent or appear dimmer.

These changes illustrate the importance of light scattering in determining our daily visual experience of the sky. Understanding this helps us appreciate the complex interactions that influence the beauty of our natural world.