The Carbon Cycle and Global Warming Chapter 19

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The Carbon Cycle and Global Warming Chapter 19
2
The Carbon Cycle A Review

• Carbon is found in the atmosphere as carbon
  dioxide.
• There are several sinks for carbon including
  limestone rock, the oceans, forests, and fossil
  fuels.
• The two processes that naturally balance out the
  carbon in the world are photosynthesis and
  aerobic respiration (one releases carbon dioxide
  into the atmosphere while the other absorbs it).

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Continued

• The typical amount of carbon dioxide in the
  atmosphere is 0.036.
• The amount of carbon dioxide found in the oceans
  is significantly greater than that found in the
  air.
• Carbon dioxide in water will react to produce
  carbonic acid. This gives natural rainwater a pH
  of about 5.6.
• The pH of seawater is about 8.

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What is the greenhouse effect?

• Some of the light energy reaching the earth from
  the sun is converted into infrared radiation
  (heat) as it reaches the surface of the earth.
• Clouds, water vapor, and gases (like CO2) are
  heated when they absorb this energy as it is
  transmitted back to space.
• The clouds and greenhouse gases then radiate out
  the infrared energy in all directions.
• Some of this energy radiates back into space, but
  some warms the earths surface and troposphere.

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Greenhouse gases-molecules in the atmosphere
which help to trap infrared radiation

• Carbon dioxide
• Water
• Methane
• Chlorofluorocarbons
• Nitrous oxide
• Carbon tetrachloride
• Halons
• Hydrofluorocarbons
• Hydrochlorofluorocarbons

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Comparison of heat trapping capacities

• Substance Length of time Heat factor
• Carbon dioxide 50-500 years 1
• Methane 9-15 years 24
• Nitrous oxide 120 years 360
• CFCs 11-20 years 1500-
• 7000

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Some factors actually help to cool the Earth

• Evaporating water absorbs heat, rises, condenses
  high up in the atmosphere where it releases heat
  ? helping to cool the earth
• Cloud cover helps to cool the earth (reflects
  light back into space before it is converted into
  heat)
• Albedo effect (light colored surfaces reflect
  heat back to space). Ice/snow are especially
  important for this.
• Aerosols (suspended liquid particles) and dust in
  the atmosphere also help to cool the earth (this
  is mainly from pollution and volcanic activity).
  Some volcanoes (like Mt. Pinatubo in the
  Phillipines) have released so much ash that they
  have lowered the average temperature measurably.

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Carbon dioxide levels and Global Warming

• Is there a connection between the rise in global
  levels of carbon dioxide and rise in global
  temperature?
• Carbon dioxide levels have been recorded at Mauna
  Loa observatory in Hawaii since the 1950s.
• They have noted an increase in carbon dioxide
  levels which some link to increased temperatures.
• Increased carbon dioxide levels are blamed on
  human activities, primarily the burning of fossil
  fuels.

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• Is this part of a natural cycle? Some evidence
  suggests that carbon dioxide levels rise
  following temperature increases.
• There have been periods of warming and cooling in
  the past (before humans had any influence).
  There are natural cycles of warming and cooling.
  Could this current period of warming be part of a
  natural cycle? Possibly connected to solar
  cycles (changes in solar radiation coming from
  the sun)?

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Measuring Climate Change

• Ice core samples
• Sediment core samples
• Current temperature data and trends
• World-wide data
• Reaching a consensus
• IPCC

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How May Humans Be Influencing Global Climate
Change?

• IPCC report in 2007 says that it is very likely
  that the troposphere is getting warmer and that
  human activities are largely responsible.
• Increase in certain greenhouse gases associated
  with human activities, especially the burning of
  fossil fuels.
• Other activities include
• Deforestation and clearing of grasslands
• Raising of livestock which release methane in
  digestion
• Rice paddies and use of inorganic fertilizers
  which release nitrous oxides

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Evidence of a warming world

• 20th century was the hottest on record in past
  1000 years. Global average rise in temperature
  is 0.6 degrees Celsius.
• Glaciers and sea ice are melting and shrinking at
  rates faster than they can be reformed.
• The worlds average sea level has risen between
  4-8 inches in the last century.
• Plants have been observed blooming earlier in
  spring.
• Migrating animal species may arrive too late for
  their food source

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Ice Caps MeltingSo what??

• Polar ice caps and glaciers have a high albedo.
• If there is less snow and ice, there will be less
  of an albedo effect and more warming.
• More warming means less snow and ice and so on.
• Melting glaciers and land ice will contribute to
  sea level rise.
• Melting floating ice does not contribute to sea
  level rise, but will affect the salinity of salt
  water and can affect currents and weather
  patterns.
• The poles experience greater climate change than
  anywhere else. Biggest concerns are ice sheets
  in Greenland and Antarctica.
• Reduction in glaciers means reduction in fresh
  water supplies.

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Melting permafrost in Alaska

• Releases large amounts of carbon dioxide and
  methane from the soil (both are greenhouse
  gases).
• Damages man-made construction.
• Trees are dying and bent over.
• Spruce bark beetle is becoming prominent.
• Economic benefits include longer growing season
  and more tourist dollars.

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Polar Bears

• Extinct by the next century??
• Melting sea ice makes it difficult for them to
  hunt for seals
• Melting ice increases likelihood of drowned bears.

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Effects of Global Warming

• Sea level rise (from melting glaciers and land
  ice and thermal expansion of water)
• Salt water intrusion
• Extreme weather
• Loss of biodiversity
• Agriculture changes (areas become warmer and
  drieragricultural belts moving north?)
• Human Population (will it crash?)
• Human Health (diseases from the tropics moving
  north?)
• Forests
• Water Resources (increases evaporation and
  changes rainfall patterns)
• See page 507 for effects as temperature rises.

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Global Oceanic Conveyor Belt

• Shallow and deep water ocean currents are
  connected and act like a conveyor belt
  transferring carbon dioxide and warm and cold
  waters between the surface and the abyss and
  between the poles and the tropics.
• Differences in temperature and salinity (creating
  density differences) contribute to the rising and
  sinking of the water and its movement.
• If too much land ice melts, this could change the
  salinity of the water in the conveyor belt,
  slowing or disrupting its flow, possibly leading
  to a global cooling for some areas.

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Slowing Global Climate Change

• Three essential prevention strategies
• Improve energy efficiency
• Switch to renewable energy resources
• Prevent deforestation of tropical forests
• Reducing population increases would enhance the
  effects

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Other Suggestions

• Carbon Capture and Storage (CSS) Remove carbon
  dioxide from smokestacks where coal is burned and
  store it.
• Geoengineering
• Use balloons, planes to inject sulfate particles
  into the stratosphere to reflect sunlight
• Pump up nutrients from the bottom ocean to create
  massive algae blooms to remove carbon dioxide
• Wrap glaciers in insulating material to slow
  melting

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Kyoto Protocol

• 2,200 delegates from 161 nations met in Kyoto,
  Japan in 1997 to negotiate a treaty to slow
  climate change.
• Requires that 36 developed nations reduce
  emissions of greenhouse gases including carbon
  dioxide, methane, and nitrous oxide (5.2 below
  1990 levels).
• Businesses can earn and trade credits to help
  with the associated costs.
• The United States did not sign.
• It is hoped that rapidly developing nations will
  join in the next phase.