Download Earth’s Climate System and Natural Change

Earth’s Climate System
and Natural Change
8.1 – Weather and Climate
Key Terms
• The atmosphere is a layer of gases that
surround the Earth. Without it our days
would be too hot and our nights too cold.
• Weather is the condition of the atmosphere
in a specific place at a specific time. It
describes factors such as wind, temperature
and moisture.
• Climate refers to the condition of the
atmosphere over a large area, averaged over
many years.
Describing the Weather
• Weather is studied by meteorologists
• They analyze the following data:
– Temperature
– Type and amount of precipitation
– Wind speed
– Relative humidity
– Atmospheric pressure
– Presence of fog, mist, or cloud cover
Predicting the Weather
Weather data is
collected using :
•Aircraft
•weather balloons
•Satellites
•Weather stations
What Causes the Weather?
• The interactions between water and air on Earth
and energy from the Sun!!!
– Energy from the Sun heats Earth’s atmosphere,
creating winds and other air movement
– Water in oceans, lakes, and rivers evaporates, cools,
and condenses which forms clouds and precipitation
– Ocean water moves in currents from the poles to the
equator and back again
• All these movements combined create weather!
What is Climate?
• Climate is the usual pattern
of weather in a region over
a long period of time (30
years +)
• Climate gives a range of
temperatures that you can
expect at different times
of the year, as well as
types and amount of
precipitation
• Climate also determines
the types of plants and
animals that live in the
area
8.2 – Classifying Climate
Climate Zones and Ecoregions
• Climate zones are areas
that are identified as having
similar temperatures,
precipitation rates/types,
and plant types
• (see Fig 2 on p.322)
• E.g the Arctic and Antarctic
are in the Polar climate
zone
• Ecoregions are new climate
zones developed to reflect
the ecology of the region
• They were first developed
due to concerns over
survival of ecosystems
• They are based on
landforms, soil, plants, and
animals, as well as climate
• They also consider human
factors like crops and cities
Describing Climates
There are three major climate zones:
Tropical Zone
• warm temperature which does not vary much throughout the year
Temperate Zones (north and south)
• temperatures vary greatly throughout the year, many regions have
warm and cold seasons
Polar Zone (north polar zone and south polar zone)
• cold temperatures, covered in ice for most or all of the year
Climate zones are caused by unequal warming of Earth’s surface.
Polar regions receive less intense sunlight than equatorial regions
do, and therefore they are colder than equatorial regions.
Climate Zones
Ecoregions
Climatographs
A climatograph is used to compare climates in different regions. It is a
graph of climate data for a particular region based on average
measurements taken over several years.
A climatograph includes figures for average monthly temperature and
an average of the total monthly precipitation.
How to Read a Climatograph
Figure 7.15 shows a climatograph for Manokwari in Indonesia. The horizontal
axis of the climatograph indicates the 12 months of the year. Temperature in
(oC) is calibrated along the right vertical axis. Precipitation (in mm) is
calibrated along the left vertical axis. This climatograph indicates that the
average temperature in Manokwari remains close to 25oC throughout the
year. Rainfall levels are high, with one wet season and one drier season in the
year.
Factors Affecting Climate
1. Distance from the equator (latitude)
2. The presence of large bodies
of water
3. Ocean or air currents
4. Land formations
5. Height above sea level (altitude)
8.3 – The Sun Powers Earth’s
Climate System
The Balance of Energy on Earth
• Almost all energy on Earth comes from the Sun.
• The sun emits different types of radiation (see
figure 2), including:
– Ultraviolet radiation (invisible, short wave, high
energy)
– Visible light
– Infrared radiation (invisible, long wave, low energy)
Figure 2: The Sun’s electromagnetic spectrum
Where does the Energy go?
• When the Sun’s radiation enters Earth’s
atmosphere, 30% of that energy is reflected back
into space by clouds, particles in the air, and the
surface of the Earth itself
• The remaining 70% is absorbed by the Earth’s
surface, clouds, and certain gases in the
atmosphere.
Latitude and Climate Zones
• Climate is colder the further away you are from the
equator
• This distance from the equator is called the latitude
• Near the equator, the Sun shines directly overhead,
so the Sun’s energy is concentrated in a small area
and feels very strong
• Closer to the North and South poles, the Sun is not
directly overhead, so the Sun’s energy is spread over
a larger area, and therefore feels weaker
8.4 – Components of Earth’s
Climate System
Components of the Climate System
• There are 4 main components of Earth’s climate
system:
– The atmosphere
– The hydrosphere
– The lithosphere
– Living things
The Atmosphere
• Made of layers of gases
wrapped around the
Earth
• Air is 78% N, 21% O2, and
1% made of traces of Ar,
CO2, He, H, and O3
• The atmosphere reflects,
absorbs, and transmits
some of the Sun’s energy
• Once the energy reaches
the surface of the Earth,
the atmosphere traps
most of it, creating a
warming of the Earth’s
surface
• This allows life to exist as
we know it!!!
The Case for Ozone
• Since the Sun is potentially dangerous, ozone in
the atmosphere prevents most of the harmful
rays of the Sun from reaching us
• In the stratosphere, ozone absorbs UV radiation
from the Sun
• A recent (30 years +) concern is the thinning of
the ozone layer over Antarctica and the Arctic
• This is caused by human made compounds called
CFC’s (chlorofluorocarbons)
CFC’s and Ozone
• CFC’s were originally used in spray (aerosol) cans,
refrigerators, and air conditioners
• CFC’s travelled up to the stratosphere where the
chlorine in the CFC’s reacted with ozone
molecules
• The chlorine acts as a CATALYST, which means it
can be used again and again in the breakdown of
ozone
• This lead to the signing of the Montreal Protocol
in 1987
Ozone in the Troposphere
• In the troposphere, UV radiation reacts with
exhaust from cars to produce ozone
• Unfortunately, in this layer of the atmosphere,
the ozone is toxic
• It causes photochemical smog
– Harmful to human health
– Damages buildings
– Affects plants and animals
The Hydrosphere
• Includes liquid
water, water
vapour, and ice
• Water in all these
forms can reflect,
absorb, and
transmit energy
from the Sun
Water and Climate
• Water absorbs and stores more thermal energy
than land
• Areas near lakes/oceans are cooler in the
summer and warmer in the fall as stored thermal
energy is released
• Regions downwind of a body of water have more
snow in the winter because air passing over the
water can absorb water vapour, which changes
over to snow over the colder land masses
• This is known as “lake effect snow”
Ice and the Climate System
• Surfaces covered in
ice and snow reflect
more of the Sun’s
radiation
• This is called the
“albedo effect”
Ice and Snow Reflect Heat
• The light colour of ice and snow allow them to reflect solar radiation.
The amount of energy that is reflected by a surface is known
as albedo.
• Light-coloured surfaces reflect energy, and dark surfaces absorb
energy.
Example:
• Because of their large differences in albedo, the distribution of
water, ice and land on Earth’s surface greatly affects the average
global temperature.
The Lithosphere
• The Earth’s crust or land mass
• Includes all solid rock, soil, and minerals
• The land absorbs radiation from the sun
Living Things
• Living things have an effect on climate through
their life processes
• Photosynthesis and cellular respiration alter the
amounts of carbon dioxide and oxygen gases in
the atmosphere
• Some animals produce methane gas as a
biological by-product
8.6 – The Greenhouse Effect
The Greenhouse Effect
absorbed
emitted
thermal energy  atmosphere  Earth’s surface  thermal energy
Define the greenhouse effect.
The greenhouse effect is a natural process that keeps Earth’s temperatures within a
certain range. Without it Earth would be colder (34oC lower) and most of the solar
energy reaching Earth would radiate out back into space.
The Greenhouse Effect
The greenhouse effect is the natural
warming caused when gases in
Earth’s atmosphere absorb thermal
energy that is radiated by the Sun
and Earth.
The atmosphere contains
greenhouse gases and solar radiation
passes through them. Solar radiation
warms the surface of the Earth and
heat rises from the surf
Some heat is able to pass back
through the gases and some cannot.
The heat that is trapped adds to
overall global temperatures.
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http://www.youtube.com/watch?v=Xsi1_EpT3Ds&feature=related
Greenhouse Gases
• There are 5 main GHG’s
– Water vapour H20
– Carbon dioxide CO2
– Methane CH4
– Atmospheric ozone O3
– Nitrous oxide N2O
Carbon Dioxide
• The atmosphere naturally contains 0.0385% CO2,
however, human activities are drastically
increasing the amount of CO2 present
• Natural sources include volcanic eruptions,
burning of organic matter, and cellular
respiration of plants and animals
• Living things are important in the removal of CO2
as well – it is stored in tree and other plant
material
• These are called “carbon sinks”
The Carbon Cycle
Water Vapour
• Two thirds of the Earth’s
natural GH effect is caused
by water vapour
• Temperature and water
vapour are related via a
feedback loop
• This is a process where the
result acts to influence the
original process (positive
feedback)
• i.e. The cause creates an
affect that affects the
original cause
Methane, Ozone, and Nitrous Oxide
• CH4 is important in the GH effect because it can absorb
more thermal energy than a molecule of carbon dioxide
• It is produced through plant decomposition and animal
digestion
• O3 in the troposphere is a result of exhaust from cars
• It is considered toxic and contributes to the GH effect
• N2O is produced through both natural (reaction of bacteria
in soil and water) and human sources (burning of fossil
fuels)
How Do GHG’s work??
• Molecules that have 3 or more atoms, and those that have
more one type of atom, have a greater ability to react and
therefore absorb different types of energy
• In the case of the GH effect, infrared radiation reaches
these molecules which trap the infrared energy and reradiate it back out in every direction
8.9 – Long-Term and ShortTerm Changes in Climate
Continental Drift
• According to the theory of plate tectonics, Earth’s
continents have moved over the surface of the
globe for hundreds of millions of years
• This drift has influenced climate in many ways
• Ocean currents and wind patterns change, which
affects heat transfer
Winds and Energy
Wind is the movement of air from an area of high pressure to an
area of lower pressure. The air moves as wind transfers thermal
energy around the world from warm areas to cooler areas.
The movement of air affects:
• ocean currents
• precipitation patterns
Wind is caused by uneven
heating of Earth’s surface.
wind moves energy from warm  cool areas
air moves from high pressure low pressure
air moves from warm  cool areas
*** Winds disperse energy through the atmosphere.
Winds and Ocean Currents
When winds blow, energy is transferred to the surface of the ocean
and causes the water to move in surface ocean currents.
Since oceans absorb energy from the Sun, the movement of water
transfers heat around the Earth’s surface.
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Long-Term Climate Cycles
• For the last 800 000 years, Earth’s climate has
cycled between freezing ice ages and warmer
interglacial periods
• These climate cycles keep happening because
the Earth’s orbit around the sun keeps changing
Milankovitch Cycles
Earth’s Orbit (Revolution)
Eccentricity
Earth’s orbit fluctuates due to the gravitational attraction of
other planets in the solar system. Its path around the Sun
changes very slowly from elliptical to circular. This affects the
intensity of the seasons. It does not explain all of the recent
changes that have been observed and measured.
elliptical orbit – planet receives more solar radiation when
near the Sun than it does when it is farthest
A
from the Sun
circular orbit – amount of solar radiation varies less throughout
the year
B
Earth’s Tilt and Climate
The Earth’s tilt changes slightly
over time. The greater the tilt
the greater the differences in
temperature between summer
and winter.
Earth is not a perfect sphere. It wobbles slightly as it rotates on
its axis.
The wobble affects the intensity of solar energy that is received
by the northern and southern hemispheres at different times of
the year.
This causes the changes in temperature between the seasons.
Short-Term Variations in Climate
• Volcanic eruptions:
– spew rocks, dust, and gases
into the atmosphere
– These particles of SO2 reflect
the sun’s energy back out to
space
– This shades the Earth’s
surface, temporarily cooling
down the climate
Short-Term Variations in Climate
• Air and Ocean Currents:
– Changes to ocean circulation may cause changes in
climate
– This is thought to be due to the freshwater glaciers
melting from the last ice age (this water is less dense,
and stays at the surface, not allowing warmer
currents to cycle in)
– This is sometimes seen naturally (every 3-7 years) in
the El Niño phenomenon
El Niño
During El Niño years, winds
blowing west weaken and may
even reverse. When this
happens, warm waters in the
western Pacific move eastward,
preventing cold water from
upwelling. This change can alter
global weather patterns and
trigger changes in precipitation
and temperature across much of
North America.
El Niño
Effects of El Niño
8.11 – Studying Clues
to Past Climates
Observing and Recording
• Scientists have recorded temperature, rainfall,
and other climate data over the last 200 years
• Before this time, data was kept in the form of
journals, paintings, farm records, and oral
histories
• Today, proxy records are used to store natural
information that tells us what climate was like in
the past
• These records are in the form of fossils, tree
rings, layers of ice (ice cores), and coral reefs
Ice Cores
Tree Rings