Transcript SNC 2D Climate

Earth’s Climate
System
Factors Affecting Climate Change
 Earth is surrounded by a layer of gases
called the atmosphere.
 The characteristic pattern of weather
conditions within a region averaged over a
period of time is called the climate.
 Climates around the world have changed
many times over the billions of years of
Earth’s history.
Earth and the Sun
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Energy from the Sun is the most
important factor that affects climate on
Earth
Solar energy travels through space and
hits Earth. The heat makes winds, rain
and other features of weather.
The solar radiation changes: a sunspot
cycle occurs every 11 years, perhaps
the cause of climate change in the
past?
Changes in Earth’s Rotation,
Orbit and Tilt
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Eccentricity: Earth’s orbit fluctuates slightly
every 100 000 years. It’s path goes from
circular to elliptical, and back again. This
affects the length of seasons
Tilt: changes over 41 000 years about 2.4.
Currently we are at 23.44, which is at the
midpoint of the range of change.
Wobble: Earth is not a perfect sphere, so it
wobbles a bit on its axis as it rotates
Latitude on Climate
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Climate is hotter
at the equator
due to the angle
at which the
Sun’s rays hit
Earth, not how
close we are to
the Sun.
Atmosphere and Climate
 Made of mainly nitrogen, oxygen and water
vapour.
 Greenhouse Effect: natural warming caused
when gases in Earth’s atmosphere absorb
thermal energy from Sun and Earth.
 Without it, Earth would radiate it’s energy
back into space and it would be a lot colder
on Earth.
Winds
 Wind is the movement of air from an area of
high pressure to an area of low pressure.
 Wind starts as an uneven heating of the
Earth’s surface.
 This in turn affects precipitation and ocean
currents.
Winds and Ocean Currents
 Energy from the moving air is transferred
to the surface of the water, causing the
water to move.
 Winds blow in fairly constant directions
around the Earth’s surface, called
prevailing winds.
Winds Affect Precipitation
 When air masses meet, usually one moves
over the other.
 The rising air cools, and any water vapour in
the air condenses to form precipitation.
 Jet streams are high-altitude that travel long
distances at high speeds.
Hydrosphere
 Invisible water vapour and clouds of water droplets
drift through the atmosphere.
 All the water in its different forms on Earth
composes the hydrosphere.
 Oceans and lakes act as heat reservoirs because
they can hold more heat than the atmosphere can.
 Water has a large specific heat capacity (takes a
lot of energy to raise the temperature of water)
 The albedo is the amount of incident light that is
reflected by the surface of an object.
Tectonic Plates
 Earth’s outer layer is made of tectonic plates
 They move around on the slowly flowing rock
layer.
 Earth has about 12 plates
 Move a few cm each year
 Shapes of oceans and continents are always
changing.
Volcanic Eruptions
 Movement of plates produce
volcanic eruptions
 Volcanoes are usually located
at boundaries of plates.
 Ash causes solar radiation to
reflect and can have a
cooling effect on the global
climate.
 Some other types of
eruptions may raise global
temperatures due to emitting
greenhouse gases.
Human Activity
 None of the previously mentioned factors can
explain the warming trend we are experiencing
now.
 There is growing evidence that the present
change in climate is at least partly due to
anthropogenic causes. (caused by humans)
 Due to burning fossil fuels (cars, factories,
farming, home, electricity, etc) we are creating
huge amounts of greenhouse gases.