1. THE GREENHOUSE EFFECT Greenhouse Gases:
chemical compounds in the atmosphere that trap heat
they retain a proportion of the sun’s heat through the greenhouse effect.
5 major greenhouse gases:
Gas % of Greenhouse Effect
water vapour (H2O) %
carbon dioxide (CO2) 9-26%
methane (CH4) 4-9%
ozone (O3) %
nitrous oxide (N20) 2-6%

3. Greenhouse Gases Nelson Science Water Vapour: ~ 60% of GG
quantity of water vapour depends on the temperature of the atmosphere
they are connected through a positive feedback loop

4. 2. Carbon Dioxide ~ 25% of GG produced from natural and human sources
volcanic eruptions, burning fossil fuels, cellular respiration in plants and animals and decomposition
carbon sinks – oceans and plants that absorb carbon dioxide from atmosphere and store it in a different form

5. The Carbon Cycle

6. 5. Nitrous Oxide (ha ha ha)
3. Methane
1 molecule of CH4 traps 23 times more GG than 1 molecule CO2
from plant decomposition in swamps and animal digestion
4. Ozone
acts as GG in troposphere when it combines with exhaust creating smog
5. Nitrous Oxide (ha ha ha)
300 times more powerful GG than CO2
from natural and human sources
released by bacteria in soil and water
released in emissions from cars and factories

7. Anthropogenic GG GG always been part of our atmosphere
major increase in past 200 years due to human activity
called anthropogenic GG
CO2 – burning fossil fuels, deforestation
CH4 – agriculture, mining, landfills
N2O – animal feed and wastes, fossil fuels

9. Short and Term Changes to Climate
earth is 4.6 billion years old
climate is constantly changing depending on how much of Sun’s energy gets absorbed
Long Term Changes
thousands/millions of years
plate tectonics – continents drift changing wind and ocean patterns, collide forming new mtns

10. Ice Ages - past 800 000 years earth cycled between ice ages and warming periods

11. Causes:
Eccentricity - Earth’s orbit varies from elliptical to circular, yr cycle
Tilt – tilts back and forth on axis, yr cycle
Wobble – slowly wobbles as it spins on its access, yr cycle

12. Short Term Variations 100’s – 1000’s of years Volcanic Eruptions
put dust and particles in air - blocks sunlight and cools earth
Air and Ocean Currents
thermohaline circulation affected by fresh water from melting glaciers
El Nino/La Nina – change in direction of prevailing winds changing ocean currents, occurs every 3-7 yrs

13. Feedback Loops
the problem creates and effect that impacts the original problem
Positive Feedback – effect increases original problem
Negative Feedback – effect decreases original problem. eg. thermostat controls temp

14. Water Vapour Feedback
water vapour enters the atmosphere when the climate warms up.
it’s a GG, so causes the climate to warm up even more.
if the climate cools down, less water vapour forms and the climate cools further

15. Albedo Effect proportion of radiation reflected by a surface
ice has a high albedo because it reflects back most UV rays
If Earth’s average temperature drops slightly, more ice forms.
reflects more of the Sun’s radiation, and Earth’s temperature decreases even more
If Earth’s average temperature increases, more ice melts.
More of the Sun’s radiation is absorbed, and Earth’s temperature increases more.
Nelson Science