3.2 Ins and Outs of Earth's Energy Budget

Summary

This lesson explores Earth's energy budget, focusing on how energy flows in and out of the Earth's climate system. It highlights key processes, such as solar radiation absorption, reflection, and emission, alongside the role of the atmosphere and greenhouse gases. The balance of energy flows is crucial for understanding Earth's temperature changes. The lesson also covers how some energy leaves the surface through radiation, evaporation, and heat transfer, emphasizing that Earth's surface is currently gaining energy, which may impact future climate conditions.

Takeaways

• 🌍 Earth's energy budget involves understanding how energy flows in and out of the climate system.
• ☀️ The Sun provides solar radiation, with 341.50 watts per meter square reaching the top of Earth's atmosphere on average.
• 🌥️ About 79 watts per meter square of incoming solar energy is reflected by clouds, particles, and the atmosphere itself.
• ❄️ Earth's surface also reflects 23 watts per meter square, especially from reflective surfaces like ice and deserts.
• 🌡️ Around 161 watts per meter square of solar energy is absorbed by Earth's surface, contributing to heating.
• 🔄 Approximately 239 watts per meter square is absorbed by Earth's atmosphere and surface, while the same amount is emitted back into space.
• 🌬️ Earth's surface radiates 396 watts per meter square as infrared (longwave) radiation, though only 40 watts escape directly into space.
• 🌫️ Greenhouse gases absorb much of the infrared radiation, re-emitting it in different directions and warming the surface further.
• 💧 Energy transfer also occurs through latent heat, where water evaporates from the surface and condenses in the atmosphere, releasing energy.
• ⚖️ Earth's current energy budget shows a small imbalance, with more energy being absorbed than emitted, leading to a slight warming of the planet.

Q & A

What is the main goal of the lesson on Earth's energy budget?

The main goal is to understand the processes by which energy interacts with parts of Earth's climate system and to practice checking for balance in energy inflows and outflows.

What is the importance of aligning mitigation actions with energy flows discussed in the lesson?

Any mitigation actions we choose to take have to align with the energy flows discussed in the lesson, as these flows are fundamental to understanding how we can alter energy flows to mitigate climate change.

What units are used to measure the energy flows in the figure presented in the lesson?

The energy flows are measured in units of watts per meter squared (W/m²).

How much solar radiation is emitted per square meter on the surface of the Sun?

Every square meter on the surface of the Sun emits 64 million watts.

What is the average solar radiation received at the top of Earth's atmosphere?

The average solar radiation received at the top of Earth's atmosphere is about 341.5 watts per meter squared.

What types of particles and objects in the atmosphere are responsible for reflecting solar radiation back to space?

White fluffy clouds, tiny particles, and droplets in the atmosphere act like little mirrors and reflect away some of the incoming solar radiation.

How much of the incoming solar radiation is absorbed by the atmosphere and what gases are responsible for this absorption?

The atmosphere absorbs some of the incoming solar radiation, with ozone in the stratosphere absorbing much of the ultraviolet and water vapor capable of absorbing some particular wavelengths of infrared radiation.

What percentage of incoming solar radiation is reflected back to space and what does this imply?

About 30% of the incoming solar radiation is reflected back to space, which implies that 70% is absorbed either by the atmosphere or Earth's surface.

How does the presence of greenhouse gases affect the radiation balance of Earth's surface?

The presence of greenhouse gases slows the passage of radiation from Earth's surface to space, increasing the total inflow of energy to Earth's surface and warming it.

What are the two ways energy leaves Earth's surface according to the script?

Most of the energy leaves Earth's surface via radiation, but some leaves via latent heat transfer or as thermals.

Is Earth's energy budget in balance according to the numbers provided in the script?

According to the numbers provided, Earth's energy budget is out of balance by about 0.9 watts per meter squared, indicating that Earth is gaining energy.