Earth's energy budget

Summary

Dr. Elinor Martin from the University of Oklahoma's School of Meteorology explains the Earth's energy budget, which is crucial for maintaining a habitable climate. She discusses the balance between incoming solar radiation and outgoing longwave radiation, emphasizing the impact of atmospheric gases like ozone and greenhouse gases on this balance. The lecture highlights how an increase in greenhouse gases since the early 1900s has led to global warming, drawing parallels to Venus's 'runaway greenhouse effect.' It also touches on the roles of clouds, aerosols, and land use in influencing the Earth's energy balance.

Takeaways

• 🌍 The Earth's energy budget is essential for determining the planet's globally averaged temperature and maintaining a livable environment.
• ☀️ The balance between incoming shortwave radiation from the sun and outgoing longwave radiation from the Earth keeps the planet's temperature stable.
• 🔥 If the Earth's energy budget shifts, either warming or cooling occurs, which affects global temperatures.
• ❄️ Bright surfaces like snow, ice, and desert sands reflect most of the incoming solar radiation, while dark surfaces like forests and asphalt absorb it.
• 🌡 Without an atmosphere, the Earth's surface temperature would be about 0°F, making life unsustainable.
• 🌫 Greenhouse gases such as water vapor, methane, and carbon dioxide absorb longwave radiation, trapping heat in the atmosphere and warming the planet.
• 🛡 Ozone in the atmosphere absorbs harmful ultraviolet (UV) radiation from the sun, protecting living organisms on Earth.
• 🚨 Human activities have increased the concentration of greenhouse gases since the early 1900s, contributing to global temperature rises.
• ☁️ Clouds play a dual role in the Earth's energy budget: they reflect solar radiation, cooling the Earth, but also absorb longwave radiation, contributing to warming.
• 🔬 Scientists are investigating how factors like aerosols, land use changes, and cloud behavior influence the Earth's energy balance and future climate.

Q & A

What is the Earth's energy budget and why is it important?

The Earth's energy budget is the balance between incoming shortwave radiation from the sun and outgoing longwave radiation from the Earth. It is crucial because it determines the globally averaged temperature of Earth, which in turn affects the planet's habitability.

How does the Earth maintain a balance in its energy budget?

The Earth maintains an energy balance when the amount of incoming solar radiation is equal to the amount of outgoing longwave radiation.

What would happen to Earth's temperature if there were no atmosphere?

Without an atmosphere, Earth's surface temperature would be about 0°F, unable to support life, as all longwave energy emitted by the Earth would pass directly back out to space.

What is the role of greenhouse gases in the Earth's energy budget?

Greenhouse gases like water vapor, methane, and carbon dioxide are transparent to incoming shortwave radiation but opaque to some wavelengths of outgoing longwave radiation. They trap heat in the atmosphere, causing Earth's temperature to increase.

How have greenhouse gas concentrations changed since the early 1900s?

Since the early 1900s, concentrations of greenhouse gases such as carbon dioxide and methane have risen, leading to an increase in the Earth's surface and atmospheric temperature.

What is a 'runaway greenhouse effect' and how did it affect Venus?

A 'runaway greenhouse effect' is a scenario where the warming caused by greenhouse gases leads to more evaporation and further warming, creating a cycle. On Venus, this effect caused the surface temperature to rise to around 872°F, making it the hottest planet in our solar system.

How do clouds impact the Earth's energy budget?

Clouds can both cool and warm the Earth. They reflect about 24% of incoming solar radiation back into space, cooling the Earth, but they also absorb longwave radiation emitted by the Earth, which warms the Earth.

What is the significance of the Earth's surface characteristics in the energy budget?

Surface characteristics like the reflectivity of snow, ice, and desert sands versus the absorbency of forests and asphalt affect how much solar radiation is reflected or absorbed, influencing the energy balance.

How do aerosols affect the Earth's energy budget?

Aerosols, such as dust and air pollution, can reflect, scatter, and absorb energy and heat, impacting the Earth's energy budget by altering the amount of solar radiation reaching the surface and the longwave radiation being trapped.

What role does land cover and land use change play in the Earth's energy budget?

Changes to land cover and land use, such as urbanization and agriculture, can affect the energy budget by altering the surface's albedo, evapotranspiration rates, and the amount of heat stored or released.

Why is it important to understand the Earth's energy budget for predicting future climate change?

Understanding the Earth's energy budget is essential for predicting future climate change because it helps scientists model how changes in solar radiation, greenhouse gases, cloud cover, and land use will affect global temperatures.