Transcript Atmosphere and Climate - IBGeography

Atmosphere and Climate
Chapter 7
THE ATMOSPHERE
The Atmosphere
 Many nearby planets, like Mars and Venus,
are barren and lifeless.
 What allows life on Earth?
The earth has an atmosphere.
 The atmosphere is a thin layer of gases that
surrounds the Earth.
 It extends from the surface of the earth to
hundreds of kilometers above the surface.
The Atmosphere
 The atmosphere is 78% Nitrogen and 21%
oxygen.
 The remaining 1% is made up of water
vapor, argon, carbon dioxide, neon, helium,
and other gases.
 We call this entire mixture air.
 The most important of the air’s gases are
oxygen and carbon dioxide
The Atmosphere
 The Earth’s atmosphere also protects living
things from most of the sun’s harmful
ultraviolet radiation.
 At the same time, the atmosphere allows
visible light to reach the Earth’s surface,
supplying energy and making
photosynthesis possible.
 The atmosphere also radiates some heat
back to Earth, thereby warming the planet.
The Atmosphere
 The atmosphere is divided into 5 individual
layers.
 The layers become less dense the farther
they are from earth’s surface.
1. Troposphere
 It extends from the earth’s surface to about
6-10miles above the surface.
 It contains nearly 90% of the atmosphere’s
gases.
 The air we breathe is part of the
troposphere.
 It is also the layer in which most weather
occurs.
2. Stratosphere
 The air in the stratosphere is less dense.
 Commercial airliners often travel in the lower
part of the stratosphere.
 It contains the ozone layer, which protects
us from harmful UV light from the sun.
3. Mesosphere, 4. Thermosphere &
5. Exosphere
 The gases in these layers become thinner
and thinner until the exosphere merges with
outer space.
CLIMATE
Climate
 Weather is simply what is happening in the
atmosphere at a particular place at a particular
moment.
 Climate, on the other hand, is the average weather
in an area over a long period of time.
 Important aspects of climate are: temperature,
humidity, wind, and precipitation.
 Climate, particularly temperature and precipitation,
determines what types of organisms are able to
live in a region.
What determines climate?
 Climate is determined by a variety of factors,
including latitude, air circulation, ocean
currents, and the local geography of an
area.
 The most important of these factors is
latitude.
Latitude
 Latitude is the distance from the equator,
measured in degrees north or south of the
equator.
 The equator is defined as 0°.
 The most northerly latitude is the North
Pole, at 90° north, while the most southerly
is the South Pole, at 90° south.
Latitude
 Latitude strongly
influences climate
because of the amount
of solar energy an area
receives depends on
its latitude.
 More solar energy falls
on areas near the
equator that on areas
closer to the poles.
Atmospheric Circulation Patterns
 There are three important properties of air
that will help in the understanding of how air
circulation affects climate.
1. cold air sinks and warms as it sinks
2. warm air rises and cools as it rises
3. warm air can hold more water vapor than
cold air can.
Atmospheric Circulation Patterns
 Solar energy heats the ground, which
warms the air above it.
 The warm air rises and cooler air moves into
replace it.
 Heating of the atmosphere therefore causes
wind, or the movement of air within the
atmosphere.
 Because different latitudes receive different
amounts of solar energy, the patterns of
global circulation result.
Atmospheric Circulation Patterns
Ocean Circulation Patterns
 Ocean currents have a great effect on
climate because water holds large amounts
of heat.
 The movement of surface ocean currents is
caused largely by winds and the rotation of
the earth.
 These currents redistribute warm and cool
masses of water.
Ocean Circulation Patterns
Seasonal Changes in Climate
 The seasons are a result of the Earth’s orbit
around the sun.
Seasonal Changes
 The Earth is tilted at about 23° relative to the path
of its orbit.
 This tilt means that the angle at which the sun’s
rays strike the earth changes as the earth moves
around the sun.
 During spring and summer in the Northern
Hemisphere, the N. hemisphere tilts toward the
sun and receives concentrated, direct sunlight.
 During fall and winter, the situation is reversed.
Seasonal Changes
 The four seasons familiar to many people in
the world do not occur in the tropics, which
are regions close to the equator.
 The temperatures are high and constant
throughout the year because most areas
receive nearly direct sunlight year-round.
Greenhouse Earth
The Greenhouse Effect
 The Earth is similar to a greenhouse. The
atmosphere acts like the glass.
 As heat radiates up from the earth, some of
it escapes into space.
 The rest of the heat is trapped by gases in
the troposphere and warms the air.
 This process is called the GREENHOUSE
EFFECT.
The Greenhouse Effect
 Not every gas in our atmosphere traps heat
this way.
 The gases that do trap and radiate heat are
called greenhouse gases.
 The major greenhouse gases are water
vapor, carbon dioxide, chlorofluorocarbons
(CFCs), methane, and nitrous oxide.
 After water vapor, carbon dioxide is the most
important of the greenhouse gases.
Carbon Dioxide
 In 1958, a geochemist named Charles
Keeling began to measure the amount of
carbon dioxide in the earth’s atmosphere.
 He noticed that during the winter months,
carbon dioxide levels rose and during the
summer months they dropped.
 After only a few years of measuring, it was
apparent that the levels were getting higher
in the winter and not dropping as much in
the summer.
Carbon Dioxide
 What might be the cause of the rise and fall of the
level during the winter and summer months?
Plants use carbon dioxide to grow, so...
During summer months the levels drop and
during the winter months they rise. It is in
correlation with the amount of plant growth.
Carbon Dioxide
Where is the extra Carbon Dioxide
coming from?
 Fossil fuels come from plants that have been
buried for millions of years.
 These plants become coal, oil, or natural gas.
 When they are burned, they release the stored
carbon as carbon dioxide.
 Millions of tons of carbon dioxide are poured into
the atmosphere each year.
 There is also a significant release of carbon
dioxide from the burning of large areas of forest.
Greenhouse gases and the Earth’s
temperature
 Since greenhouse gases trap heat near the
Earth’s surface, many scientists think that
the increase in carbon dioxide has resulted
in an increase in Earth’s temperatures.
 This predicted increase in temperature is
called GLOBAL WARMING.
A Warmer Earth
 Scientists are not sure how quickly the earth
will warm or how severe the effects will be.
 Different computer models give different
answers to these questions.
A warmer Earth
 If the Earth heats up significantly, the
oceans will absorb more heat energy, which
makes hurricanes and typhoons more
common.
 Scientists are also concerned that the ocean
currents may change, leading to droughts in
some areas and major flooding in others.
A Warmer Earth
 As polar regions warm, more icebergs may
break loose from glaciers and melt in the
sea.
 Sea levels would then rise, not only from
melting ice but also the water expands as it
warms.
 As a result of higher sea levels, some
coastal areas might be covered with water.
The Ozone Shield
 The stratosphere contains the Earth’s ozone
shield.
 Ozone is a form of oxygen with molecules made of
three oxygen atoms.
 Ozone absorbs most of the UV light from the sun.
 UV light is very harmful to organisms because it
can damage the genetic material in living cells.
 The ozone layer is like “sunscreen” for the earth.
Ozone Eaters
 CFCs (chlorofluorocarbons) were thought to
be miracle chemicals.
 They are nonpoisonous, nonflammable,
non-corrosive metals.
 At Earth’s surface, CFCs are chemically
stable.
 CFCs are now known to destroy our
protective ozone layer.
The Ozone Hole
 Data collected by satellites since 1979
shows a significant decrease in the amount
of ozone at the poles.
 As the amount of Ozone decreases, more
UV light is able to pass through to Earth’s
surface.
 There are many detrimental effects of ozone
thinning and increased UV penetration.
The Ozone Hole
Stopping Ozone Eaters


In 1987, the Montreal Protocol called for a
sharp decrease in the production of CFCs.
In 1992, 93 countries decided upon the
following agreements:
1. Industrialized countries must eliminate CFCs
2. Industrialized agreed to help developing
countries stop using CFCs
3. Banning of other substances that were also
harmful to the ozone.