Chapter 23 - Global Ecology

Atmospheric Composition

a) 78% nitrogen

b) 21% oxygen

c) 0.93% argon

d) 0.0038% carbon dioxide

e) 0.00005% ozone

Organism Defense by Earth

Earth’s magnetic field was born 3.45 billion years ago, shielded early life from deadly solar radiation

-Allowed for early life, like anaerobes

Cyanobacteria — created the world’s largest pollution event: Oxygen

Atmospheric Envelope and Greenhouse Earth

1. Troposphere

• Earth’s surface 9-16km

• Atmospheric gases most concentrated

2. Stratosphere

• Troposphere to 50km

• Ozone is most concentrated

3. Mesosphere and Thermosphere

• Extend above stratosphere

Greenhouse Gases

Heat trapped using greenhouse gases (water, carbon dioxide, methane, ozone, nitrous oxide, CFCs)

-Without greenhouse gases, average temperature would be -18C

-30% incoming solar radiation are reflected into space due to greenhouse gases, done by clouds/particulates

Atmosphere and Solar Energy

70% of solar energy is absorbed by atmosphere or earth’s surface, then:

1. Re-emitted as infrared radiation

2. Absorbed by greenhouse gases

3. Radiated back to Earth