evr- climate change 1

– Earth’s radiative balance – Solar forcing – Greenhouse gases – Climate change feedbacks – Climate models – What is responsible for climate change?

Black body radiation

The electromagnetic radiation emitted by the Earth and sun

1. The amount of solar radiation reaching the Earth’s atmosphere is affected by changes in solar output (sunspots, etc.) and changes in the Earth’s orbit (Milankovitch cycles)

2. The fraction of light that Earth’s atmosphere reflects back to space (the atmosphere’s albedo) is affected by the concentration of aerosols and the amount, type, and height of clouds.

3. The fraction of light that gets absorbed by the atmosphere is determined by the chemical composition of the atmosphere and the cloud cover

4. The fraction of light absorbed or reflected by the atmosphere is determined by many feedbacks with the Earth’s albedo

5. Evapotranspiration and thermals transport heat energy from the surface to the atmosphere

6. The long-wave (infrared) radiation emitted by the Earth is determined by the Earth’s temperature

7. Greenhouses gases absorb a substantial fraction of the long-wave radiation emitted by the Earth’s surface

8. Most of the energy absorbed by the atmosphere gets radiated back to the Earth’s surface

9. A small proportion of the energy emitted by the Earth’s surface can pass directly through the atmosphere and be emitted into space (this fraction will be determined by the concentration of greenhouse gases and clouds in the atmosphere)

10. Some gets radiated from the atmosphere into space

Why is Earth’s climate changing due to Earth’s radiative balance (refer to diagram for clarity)

True

T/F: Heat ≠ Temperature

Heat capacity

the ratio of heat added to an object to the increase of temperature of that object

Is heat capacity of air or water greater ?

Water, can contain more heat based on volume

Changes in solar output (sunspots, etc.) and changes in orbit (Milankovitch cycles)

Changes in solar irradiance (the amount of sunlight reaching

the surface of the Earth) can be due to: (2)

Aerosols

reflect, scatter, or absorb light of various wavelengths

Produced by natural processes (volcanoes, dust, sea spray) and humanity’s actions (sulphates, black carbon from fossil fuel burning)

In what 2 ways can aerosols be produced? Examples?

Sulphates

gaseous sulphate interacts with water to form sulfuric acid, which condenses on particles

1. Aerosols

2. Cloud cover

3. Greenhouse gases

What causes changes in light penetration in Earth’s atmosphere?

Clouds also reflect light back into space before it reaches the surface (impacts strength of albedos)

How can clouds cause change in light penetration?

Greenhouse gases

Transparent to visible light (wavelengths from the sun), but absorb long-wave (infrared) radiation given off by the Earth

Infrared light

Absorbed by greenhouse gases (form of black body radiation); longer wavelengths (less energy) than visible light and given off by all objects from it being BBR

Water vapor (36-72%)

– Carbon dioxide (9-26%)

– Methane (4-9%)

– Ozone (3-7%)

Greenhouse gases from most to least abundant.

1. CO2 has been increasing in the atmosphere due to the burning of fossil fuels

2. Carbon dioxide has a long life-time in the atmosphere

3. Rock weathering (slow)

Why do we focus on CO2 as a greenhouse gas?

Methane

main component of natural gas

1. A significantly stronger greenhouse gas than CO2, but still significantly lower concentrations than CO2

2. shorter lifetime in the atmosphere (Less than 11 years) than CO2

3. Removed by reacting with other molecules in the atmosphere

Characteristics of methane