1. The Greenhouse Effect

2. Review
Previously, we learned that the sun emits energy that travels to Earth
The sun’s energy is either reflected or absorbed
Some parts of our atmosphere absorb the suns energy

3. The Role of the Climate System
Without Earth’s climate system, the planet would be much colder than it is now.
The climate system helps to maintain Earth’s temperature by trapping and storing energy from the Sun and spreading it around the world.
Greenhouse Effect: a natural process whereby gases and clouds absorb infrared radiation emitted from the Earth’s surface and radiates it, heating the atmosphere and Earth’s surface.

6. What is the Greenhouse Effect?
The atmosphere allows radiation (higher-energy) from the Sun to pass through
Radiation is absorbed by the Earth’s surface
This energy becomes thermal energy and warms the surface
The surface emits infrared radiation
Gases in the atmosphere trap much of the IR radiation, radiating the energy in all directions, sending some back to the surface
This warms the surface even more

8. Non Greenhouse Gases
Most of the air is made up of nitrogen and oxygen gases
These gases do not absorb radiation from the Earth’s surface

9. Greenhouse Gases Water vapour (H2O) – most important
The greenhouse effect is caused by gases that make up a small portion of the atmosphere, known as the greenhouse gases
Water vapour (H2O) – most important
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Their contribution to the greenhouse effect is determined by their concentration and by how much thermal energy each molecule can absorb

10. Carbon Dioxide
Concentration in atmosphere: % or 385 parts per million (ppm)
Estimated to cause up to a quarter of the natural greenhouse effect
Concentration before the Industrial Revolution: 280 parts per million
Natural sources of CO2 include: volcanic eruptions, burning of organic matter and cellular respiration

11. Water Vapour Warmer temperatures mean more water in the atmosphere
About two-thirds of the greenhouse effect is caused by water vapour
Quantity of water vapour in the atmosphere depends on the temperature of the atmosphere
Warmer temperatures mean more water in the atmosphere
Colder temperatures mean less water in the atmosphere

12. Methane Methane is 23 times more powerful of a greenhouse gas than CO2
Much less methane than carbon dioxide in the atmosphere
Methane can hold much more thermal energy than carbon dioxide
Methane is 23 times more powerful of a greenhouse gas than CO2
Produced naturally from plant decomposition in swamps and animal digestion, but also human sources
Concentration before the Industrial Revolution: parts per million
It is now ppm

13. Nitrous Oxide
A Molecule of N2O is almost 300 times more effective than a molecule of CO2
It is less available than CO2 though
Concentration before the Industrial Revolution: parts per million
Risen to ppm
Produced both naturally and by human sources
Naturally through reactions of bacteria in soil and water

14. The Anthropogenic Greenhouse Effect

16. The Anthropogenic Greenhouse Effect
Anthropogenic: resulting from a human influence
If we continue to produce greenhouse gases at a similar rate, Earth’s average temperature will likely increase by 2°C to 6°C by the end of the century.
May not sound like much, but can cause dramatic impacts on species survival, habitability, and weather conditions

17. Anthropogenic Sources of Greenhouse Gases
Carbon Dioxide: burning fossil fuels (transportation, heating, electricity and industry) and deforestation
 Methane: agricultural activities (rice farming, cattle ranching), decay of organic materials in landfills and sewage treatment, coal mining and natural gas extraction
Nitrous Oxide: management of livestock feed and waste, farming using nitrogen fertilizer, industrial processes

19. Our Own Doing!!!
Chloroflourocarbons (CFCs) - There are no natural sources of CFCs.
Leak out from refrigerators, air conditioners and through other industrial processes