11.1 Natural Climate Change

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11.1 Natural Climate Change

• Science 10
• p.464-481

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Climate

• describes the average conditions of a region.
• is usually measured over 30 years or more.
• Climate clouds, precipitation, average
  temperature, humidity, atmospheric pressure,
  solar radiation, and wind.

• Climate and geography combine to allow specific
  organisms to grow.
• Biogeoclimatic zones have distinct plants, soil,
  geography, and climate.
• British Columbia has 14 distinct biogeoclimatic
  zones.

BCs climate zones
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• Paleoclimatologists study long-term patterns
• environment (using fossils)
• growing seasons (using tree rings)
• types of rainfall (using river sediments)
• air condition and composition (using glacier ice
  cores)
• Gases trapped in the ice, specifically CO2,
• reveal long-term atmospheric levels.
• Fossils and sediment evidence show Earths
  climate has changed often and drastically
• 21 000 years ago, much of Canada and northern
  Europe was under glaciers.

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• Ice core data reveal CO2 levels for the past 650
  000 years.
• Scientists have tested the atmospheric CO2 for
  the past 50 years

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Factors That Influence Climate1) Composition of
Earths Atmosphere

• Earths atmosphere is a boundary, so very little
  energy (except radiant energy) enters or leaves
• The Earths natural greenhouse effect allows a
  narrow range of temperatures.
• Solar radiation comes in, is
• absorbed, and is then emitted and
• trapped before being able to escape.
• Greenhouse gases in the
• atmosphere absorb thermal energy.
• This keeps Earth an average of 34ºC
• warmer than it would be otherwise.
• More greenhouse gases could make it too warm.

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2) Earths Tilt, Rotation and Orbit

• Earths tilt is responsible for the seasons
• In summer, we are tilted toward the Sun
• In winter when we are tilted away from the Sun

• Earths tilt varies slightly (currently 23.5º)
• When tilt is largest, climate experiences the
  largest extremes

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• Earth wobbles as it rotates on its axis.
• the axis changes so the angle of incidence of
  solar radiation also changes

• Earths revolution around the Sun is elliptical
  and changes shape.
• On a 100 000 year cycle, Earths elliptical orbit
  becomes more circular.
• When the orbit is most
• elliptical, Earth can be
• farther away from the Sun.

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3) The Water Cycle

• describes the circulation of water on, above, and
  below Earths surface.
• water vapour 70 of the greenhouse gasses in
  the atmosphere
• When temperature increases, more water evaporates
  and causes
• 1) More solar energy absorbed
• by this greenhouse gas.
• 2) More solar energy reflected
• back out to space and never
• reachs Earth.

The water cycle stores and transfers large
amounts of thermal energy.
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4) Ocean Currents

• Convection currents in the oceans move large
  amounts of thermal energy all around Earth.
• Deep ocean currents flow based on density
  differences.
• They behave like massive convection currents,
  with warm water rising in the tropics and cold
  water from the higher latitudes replacing it.

Deep-ocean currents move cold, salty water below
the surface and warm, less-salty water near the
surface.
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• Salinity and temperature change water density
• Cold water and salty water (found at the poles)
  are more dense than warm water and fresh water.
• Surface currents (0 - 200 m) are warmed by solar
  radiation.
• The thermocline is the
• region separating surface
• and deep ocean currents.
• Upwelling occurs when
• cold, deep water rises
• through the thermocline
• into surface currents.

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• La Niña is an example of upwelling.
• When this occurs, cool water at the surface of
  the Pacific Ocean causes warm winters in
  southeastern North America, and cool winters in
  the northwest.
• El Niño is the reverse warmer water on the
  surface of the Pacific Ocean results in warm
  winters in the Pacific Northwest and in eastern
  Canada.

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5) The Carbon Cycle(remember this from chapter
2!)

• Carbon dioxide is an important greenhouse gas
• 2nd most prevalent greenhouse gas
• Without CO2 to trap infrared radiation from
  Earths surface, the average temperature of Earth
  would be below freezing.

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• The carbon cycle maintains a balance of CO2 in
  the atmosphere.
• Deep oceans are carbon sinks.
• CO2 in the ocean is converted to carbonates
  (CO32-), in shells.
• Phytoplankton use CO2 for photosynthesis at the
  oceans surface.
• Weathering of rocks releases carbon.
• Carbonic acid is formed when water reacts with
  CO2 in the atmosphere.
• Forests are carbon sinks
• take in CO2 while growing but
• release CO2 when burned or
• when decaying.

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6) The Movement of Tectonic Plates, and
Catastrophic Events

• Large-scale disasters can quickly change
  atmospheric conditions.
• Erupting volcanoes can release ash and molten
  rock that absorb radiation.
• Water vapour and sulfur dioxide (changed into
  sulfuric acid) can reflect solar radiation back
  into space.

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• Meteorites and comets are thought to have caused
  dramatic changes.
• cause large amounts of dust, debris and gases in
  the atmosphere.
• Solar radiation is affected so much that it is
  thought that these events are responsible for
  some of Earths largest extinction events.
  (dinosaurs!)

Large comet and meteor collisions with Earth can
cause debris to block solar radiation and cause
changes all over the Earth.
Take the Section 11.1 Quiz