1. Greenhouse Gases & Human Activitites

2. Greenhouse Gases & Human Activities
Greenhouse gases in the atmosphere produce a warmer Earth.
CO2 concentration has increased from ppm in 1960 to 370 ppm in 2000.
ppm = parts per million (parts of one substance for 1,000,000 parts of another)

3. Greenhouse Gases & Global Warming
99% of the atmosphere is made of N2 and O2, but neither are greenhouse gases!
Greenhouse gases (GHGs) are gases that absorb and re-emit infrared radiation.
Made up of 3 or more atoms
Interact with radiation of different wavelengths
Produce warming by absorbing and emitting energy
Most abundant: carbon dioxide and water vapour

4. Sources & Sinks
Processes that add greenhouse gases to the atmosphere are called sources.
CO2 comes from natural sources such as animal respiration, and human causes such as combustion of fossil fuels and deforestation.
Process that absorb greenhouse gases from the atmosphere are called sinks.
Plants convert CO2 into stored carbon during photsynthesis, phytoplankton in the oceans absorb 30-50% of CO2 from burning of fossil fuels.

5. Composition of Earth’s Atmosphere

6. Water Vapour as a Greenhouse Gas
Water vapour accounts for 65-85% of the greenhouse effect
But… it is not caused by humans!!!
The concentration of water vapour in the atmosphere at any one time is directly related to TEMPERATURE.

7. Interaction of Water Vapour & Carbon Dioxide
The effect of one is added to the effect of the other
Positive feedback loop

8. Sources of Methane (a GHG)
Methane (CH4) is produced by bacteria that break down waste matter in oxygen-free environments:
Wetlands (bogs, swamps)
Rice paddies
Digestive processes of termites and cattle
Decomposing garbage in landfills
Processing of coal and natural gas
Tanks of liquid manure from livestock production

9. Unique Ways of Capturing Carbon from Methane
Having cattle wear backpacks to capture methane, which could then be used as fuel
Feeding cattle clover and alfalfa to reduce emissions by 25%
Switch in human diets (stop eating beef)

10. Ozone Depletion & the Ozone “hole”
Large region of declining ozone (O3) concentration since 1970
Due to addition to the atmosphere of human-made gases that contain chlorine
Results in increase in amount of UV light that reaches Earth’s surface
Positive feedback loop
Causes stratosphere to cool  formation of polar stratospheric clouds  formation of free chlorine  reduction in ozone

13. Ground-Level Ozone
Smog from reaction of sunlight and vehicle exhaust chemicals
Can cause damage to lungs and heart
Produces cracks in rubber and plastic
Can trap thermal energy, contributing to global warming

14. Halocarbons
Chemicals formed by industrial processes from carbon and one or more halogens
Best-known: chlorofluorocarbons (CFCs)
Solvents, cleaners, coolants
Absorb infrared radiation
Break apart ozone
Banned in most developed nations since 1987

15. Anthropogenic Greenhouse Effect
Increased capacity of the atmosphere to absorb and prevent the escape of thermal energy because of an increase in greenhouse gases introduced by human activities

16. Global Warming Potential (GWP)
Ability of a substance to warm the atmosphere by absorbing thermal energy
Depends on:
Concentration of the gas in the atmosphere
Ability of the gas to absorb heat
Length of time the gas remains in the atmosphere

17. How Can We Reduce Greenhouse Gas Production?
Conserve electricity
Energy-efficient light bulbs and appliances
Improve home heating efficiency
Thermostat settings, insulation
Reduce, re-use, recycle
Garbage

18. Homework
Pg #1-4
Pg Activity 8.3
Pg #5-8
Pg #1-8