Transcript Ch12 Climate Change and Humans

Ch12 Climate Change
and Humans
Can we reduce our impact on the
biosphere and still meet human
needs?
How does global warming
affect the polar bear?
 Seals are a very important part of their
springtime diet.
 Getting seals is totally dependent on a
strong ice pack reaching the shore.
 With global warming the pack ice reaches
shore lots fewer days = less seal hunting
 Polar bears are showing signs of not
enough to eat – they are getting smaller
and leaner
Natural Greenhouse Effect…
 Is why there is life on earth!
Not NOT
caused by humans.
 65% of re-radiation of sun’s
back to Earth occurs
owing to H2O VAPOR.
heat
naturally
 This is STILL THE MOST ABUNDANT
GREENHOUSE GAS
Enhanced Greenhouse Effect
 Extra green house effect caused by
human activity
Greenhouse Gases
 1. Water vapor ( contributes 65% of re-radiation)
 2. carbon dioxide (contributes 25% of re-radiation)
 3. methane
 4. nitrous oxides
 5. halocarbons (i.e. CFCs)
 6. others

Human produced GGs
Global warming potential of a
greenhouse gas depends on:
 1. Amount of gas entering atmosphere/year
 2. Lifetime of gas in atmosphere
 3. Effects of gas on atmospheric chemistry
 4. Effect of gas on other atmospheric gases
Carbon Dioxide
 Most abundant greenhouse gas that contributes to the
ENHANCED greenhouse effect
 Found in:
 Atmosphere
 Fossil Fuels
 Carbonates in limestone,
shells
and Earth’s crust
 Hydrocarbons in oil and
natural gas
 Organic compounds in live and decaying organisms
 Hydrogen carbonates dissolved in water
The Carbon Cycle
 Most carbon is in:
 Soils, fossil fuels and
cement
 Surface Ocean
 Deep Ocean
Carbon sinks i.e. fossil
fuels,
forests, soil, oceans, are reservoirs of carbon and CO2
and keep it cycling and out of atmosphere
Environmental Concerns
 LEVELS OF ATMOSPHERIC CO2 ARE 37% HIGHER
THAN IN 1750
 75% OF THIS INCREASE HAS OCCURRED IN THE
LAST 75 YEARS
 CAN LIFE ADAPT TO THIS RAPID RATE OF
CHANGE????
Other Greenhouse Gases of
Concern
 Methane – CH4
 Called natural gas because produced by bacterial
decay of organic matter
 Of concern because it has global warming potential 25x
that of CO2
Methane
 Used for heating homes and buildings, generates
electricity
 Concentration in atmosphere  146% since 1800
 Trash generator
Cow-poop generator!
Methane Hydrate
 Only in deep cold oceans, but estimated to 2x the
amount of carbon found in all fossil fuels.
Nitrous Oxide
 Concern: Has global warming potential 300x
that of CO2
 From bacterial breakdown of fertilizers, and burning of
fossil fuels at very high temperatures
Halocarbons
 Carbon compounds containing halogens (Cl, F, Br) i,e,
CFCs……
 Used for refrigerants, coolants, fire extinguishing ;
 Concern: thin the ozone layer, global warming potential
is 12000 to 15000x greater than CO2
Human effect on Global
Climate Change
 DEFORESTATION = Increases Global warming
 25% of global CO2 emissions
 Forests are important since they absorb radiation and
cool surrounding area
 Forests remove atmospheric CO2 for Photosynthesis
 CITIES = urban heat islands, increase atmospheric
temperature
Predicting Climate Change
 GCMs General Circulation Models
 3D mathematical predictive models of land, air and
oceans done by supercomputers
 Canadian GCM1 predicts increase of over 4oC over the
21st century
Factors influencing future
greenhouse gases in the
atmosphere
 Future human population growth
 Energy use per person
 Types of energy used and amount of
greenhouse gases each energy type
generates
 Choices we make
 Natural events: i.e volcanic eruptions
If CO2 emissions doubled what will happen
to Canadian biomes?
 Tundra and Taiga range will 
 Temperate deciduous forest, grasslands
and desert ranges will 
What can we do?
 How can we reduce our impact on
the biosphere and still meet human
needs?