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Earth’s Dynamic Climate
The Science of Climate Change
Is climate change new?
• Climate change is a natural part of Earth’s
history.
– For example, thousands of years ago, thick
ice sheets covered most of Canada and a
large portion of the United States.
Increased Temperature
• In the last 100 years the earth has warmed
by 0.74°C
• Eleven of the twelve years (1995-2006)
rank among the twelve warmest years
since 1850
• There is a risk that by the end of the 21st
Century temperatures could rise by
between 1.1 and 6.4°C.
WEATHER AND CLIMATE
• Have you ever wondered why it can rain
one minute and be sunny the next?
• Have you ever wondered why it is always
drier in central Canada than it is on the
coast?
• The reason is simple: while weather can
change quickly, with big variations over a
day, climate changes over much longer
timeframes.
• Rainfall patterns, for example, do not simply
change overnight.
• Changes in the weather are generally
well-understood and despite what
many people think, meteorologists are
pretty good at predicting what the
weather will be the following day.
Weather
• Weather is what atmospheric conditions
are present over a short period of time.
• Weather is the day-to-day state of the
atmosphere.
• Weather is thought of as the combination
of temperature, humidity, precipitation,
cloudiness, visibility, and wind.
• We talk about the weather in terms of:
– "What will it be like today?”
–"How hot is it right now?”
–"When will that storm hit our section
of the country?"
Climate
• Climate is how the atmosphere "behaves"
over relatively long periods of time.
• Climate is defined as statistical weather
information that describes the variation of
weather at a given place for a specified
interval.
• It is the weather of a locality averaged
over some period (usually 30 years) plus
statistics of weather extremes.
TEMPERATURE AND CLIMATE
Temperature and Climate
• The Earth is
surrounded by an
envelope of gases
called the
atmosphere.
• Without this envelop,
the days would be too
hot and the nights
would be too cold!
• So how is heat energy
transferred?
How is Heat Transferred?
• Heat is always
transferred from the
hotter object to the
colder object.
• There are three types
of heat transfer:
Conduction
• The transfer of heat
between substances
that are in direct contact
with one another
• The better the conductor
the more rapidly the
heat will transfer.
Convection
• The up and down movement of gases and
liquids caused by heat transfer.
• As a gas/liquid is heated it expands and
rises because it is less dense. As it rises
and expands, it cools and falls. This
creates convection currents.
Radiation
• Electromagnetic waves moving through
space. These waves come in contact with
an object and transfer the heat to the
object.
THE EARTH’S CLIMATE SYSTEMS
• The Earth’s climate system is affected by
the interactions of different subsystems
such as the atmosphere, the hydrosphere
(oceans and rivers) and the biosphere
(forests, plants and soil).
• Although individual interactions between
forests and the atmosphere are well
understood, the way all these different
subsystems interact is very complex and
much harder to understand.
Earth’s Climate Systems
What does it involve?
• Lithosphere
• Atmosphere
•Hydrosphere
These components interact with one another and with
aspects of Earth’s biosphere to determine not only day-today whether, but also long term averages, climate.
Lithosphere
• The lithosphere is the rocky layer that
covers the earth.
Atmosphere
• The atmosphere is the air that surrounds
the earth.
Hydrosphere

The hydrosphere is all the water on or near
the earth’s surface.
Factors Affecting Climate Change
1. The Sun
2. The Earth
3. The Atmosphere
4. The Hydrosphere
5. Human Activity
Factors Affecting Climate Change
1. The Sun
2. The Earth
3. The Atmosphere
4. The Hydrosphere
5. Human Activity
The Sun
• The sun is a huge globe of mostly hydrogen
(73%), the lightest of the gases. There is also
25% Helium.
• It is about 1.4 million kilometers in diameter (110
times the diameter of the earth).
• The sun is so hot (15 000 000 oC) that the gas
glows and it is this light that speeds through
space to reach and warm the earth.
The sun is all “atmosphere” because it is all gas. When people
refer to the “surface” of the sun, they are referring to the
outside glowing region called the photosphere.
• The surface of the sun (photosphere) constantly
churns and writhes.
• Solar prominences are streamers of glowing
gas that arch into space.
• Some regions on the sun are cooler than their
surrounding and therefore appear to be darker.
These are known as sun spots.
• Near sun spots are where violent solar
flares occur, sending streams of high
energy subatomic particles into space.
This outflow of particles is known as the
solar wind and can have a great affect on
the activities of earth.
Solar Energy
• Heat produces winds, rain and other features of climate.
Changes in Solar Activity
• The Sun produces a variable amount
of energy.
• When the number of sunspots is
high, the Sun emits higher amounts
of solar radiation.
• Some scientists believe that changes
in solar output are the main cause of
climate change in the past.
Factors Affecting Climate Change
1. The Sun
2. The Earth
3. The Atmosphere
4. The Hydrosphere
5. Human Activity
Factors on Earth that Affect Climate
1.Rotation
2.Revolution
3.Tilt
4.Latitude
Rotation vs. Revolution Review
• Earth rotates once
every 24 hours (1 day)
around its axis, an
imaginary line that
goes from the North
Pole to the South Pole
through the center of
the Earth.
• The Earth also revolves (orbits)
around the Sun every 365 and a half
days (1 year).
• Another important
detail is that the
Earth’s axis of
rotation is tilted at
an angle of about
23.5˚
Solar Energy and the Earth
• The amount of solar energy that reaches Earth
depends on solar activity, the shape of the Earth and
the tilt of the Earth.
Earth’s Seasons
The seasons are created by Earth’s
revolution and its tilted axis.
Latitude
• A crucial feature of the
climate system is that the
energy coming from the
sun is not distributed
uniformly across the
surface of the Earth.
• Due to the shape of the
Earth, the energy is most
intense at the equator
and weakest at the poles.
Temperatures Around the World
• This non-uniform energy distribution leads to
temperature differences.
MORE ON EARTH
Land Surfaces
• Earth’s outer layer is made of massive pieces of
solid rock, called tectonic plates.
• Earth has about 12 major plates that move at a
rate of a few centimeters per year. The plates
carry the continents with them as they move.
• This means that the shape of the oceans and
continents is always changing.
The Movement of the Continental
Plates
• Patterns of air and water circulation are
affected, which in turn affects the thermal
energy around the world.
• The formation of mountain chains also affects
the patterns of wind and precipitation around
the globe.
Volcanoes
• Most volcanoes are
located at the boundaries
of tectonic plates.
• Plate movement affects
climate by producing
volcanic activity.
• In these areas, molten
rock and gases from
below the Earth’s crust
rise up through cracks in
the rock and spew into
the air as volcanic
eruptions.
• During a volcanic eruption,
particles called aerosols (such
as ash) are released into the
atmosphere.
• Aerosols:
– reflect solar radiation and
have a cooling effect on the
global climate
– scatter light
• Some volcanic eruptions can
raise global temperatures by
releasing greenhouse gases.
Volcanic
Eruptions
Factors Affecting Climate Change
1. The Sun
2. The Earth
3. The Atmosphere
4. The Hydrosphere
5. Human Activity
Atmospheric Factors that Affect
Climate
1.Greenhouse Effect
2.Wind
The Atmosphere…
Earth’s Warm, Snuggly Blanket
• The Earth’s atmosphere is like a big blanket that
surrounds the globe keeping humans warm. If it was
suddenly stripped off, the Earth’s average
temperature would plummet and everything would
freeze.
• Like a blanket that could be made from a mix of
cotton and wool, the Earth’s atmosphere is made
from a mixture of gases.
• The atmosphere
starts at Earth’s
surface and goes up
to about 560 km into
space.
• It is mostly made of
nitrogen (N2) and
oxygen (O2) gases as
well as water vapour,
very low
concentrations of
other gases and
particles of solids.
The Earth’s
Atmosphere
•The greenhouse effect occurs
because the Sun’s shortwave
radiation passes through the
atmosphere and warms the
Earth’s surface.
•This warm surface then
radiates long wave infra-red
radiation back into space.
•The greenhouse gases absorb
some of the infrared radiation
and re-radiate it back to the
atmosphere and the ground.
• The process is similar to how a greenhouse
traps warmth and why the term greenhouse
effect has become part of everyday language.
• Any change to the volume of
greenhouse gases therefore
changes the temperature on
Earth. It is a bit like putting
an extra blanket on your bed
– it traps more of your body
heat under the covers.
• As the earth slowly warms,
the whole climate system is
affected.
Greenhouse Gases
• The main gases are nitrogen, oxygen and
argon.
• There are also trace gases such as carbon
dioxide, water vapour, methane, ozone and
nitrous oxide.
• These are called the greenhouse gases
because they create a warm environment for
the Earth.
• Some greenhouse gases such as carbon
dioxide, are constantly being added to and
removed from the atmosphere by natural
processes.
• However, the recent increase in their
concentration and the addition of new gases
due to human actions is the driving force of
changes in climate that the world is now
experiencing.
Wind
• Wind is caused by uneven heating of Earth’s
surface.
• The air moves as wind transfers thermal energy
around the world from warm areas to cooler
areas.
• It is the movement of air from an area of high
pressure to an area of lower pressure.
Prevailing Winds
• Winds blow in fairly constant directions around the
world. These are known as prevailing winds.
Wind
• Winds disperse energy throughout the
atmosphere.
• The movement of air affects:
– precipitation patterns
– ocean currents
Precipitation
• As air masses of different densities move
across the Earth’s surface, they interact.
• When air masses meet (called a front),
one air mass usually rises over the other.
• The rising air cools and any water vapour
in the air condenses to form precipitation.
• Winds start the ocean currents flowing, but
two other factors influence the patterns of
flowing waters – continents and the
Coriolis effect.
• Ocean currents turn right in the Northern
Hemisphere and turn left in the Southern
Hemisphere.
Result of all Factors that act on the
Oceans
• Looking at the diagram, you may notice the
nearly circular currents. These are called
gyres.
Ocean Currents
• The difference in atmospheric temperature cause the
ocean to react and create convection currents. These
currents transport heat from the warm tropics to the cold
Polar Regions and back again.
Factors Affecting Climate Change
1. The Sun
2. The Earth
3. The Atmosphere
4. The Hydrosphere
5. Human Activity
The Hydrosphere
• Two thirds of the
Earth is covered by
oceans.
• The hydrosphere
includes all of the
water on the planet
in its different forms.
• On Earth water is found in many forms:
– vapour and clouds of water droplets in the
atmosphere
– liquid in the oceans, seas, and smaller bodies of
water
– ice and snow in temperate and colder regions
Gas
Liquid
Solid
Specific Heat Capacity
• Oceans and lakes act as heat reservoirs. They buffer
temperatures in the atmosphere.
• Large bodies of water influence climate because
water has a large specific heat capacity compared
with other substances.
Specific Heat Capacity
• Specific heat capacity is the amount of heat
required to raise the temperature of one gram
of a substance by one degree Celsius.
• Water has a large specific heat capacity. This
means it takes more heat to raise the
temperature of 1 g of water by 1oC than it
does to do the same to many other
substances.
Specific Heat Capacity… So what?
• The higher the heat capacity, the longer it takes to
warm the substance up and the slower the substance
loses its heat.
• Water’s high specific heat capacity means that a land
mass near a large body of water will have its
temperature “moderated” by the water – it will
warm up more slowly in summer and cool down
slowly in winter than will a land mass further from
water.
The water will warm and cool more
slowly than the beach
25 degrees
20 degrees
Specific Heat Capacity
Some Common Specific Heat Capacity Values
Substance
Specific Heat Capacity in
“The number of joules of heat energy
needed to raise the temperature of 1 g
of the substance
by 1oC.”
Pure Water
4.18
Sea Water
3.89
Dry Air
1.00
Wet mud
2.51
Sandy soil
0.92
Snow and Ice
• Ice and snow reflect heat
• The light colour of ice and snow allow them to
reflect solar radiation.
• Because as we know, light-coloured surfaces
reflect energy, and dark surfaces absorb
energy.
Humidity
• Absolute humidity is the actual amount of
water vapor in the air, expressed in grams
of water vapor per kg of air.
• Relative humidity is the percent of water
vapor in the air compared with the amount
of water vapor that the air would contain if
it were saturated.
Factors Affecting Climate Change
1. The Sun
2. The Earth
3. The Atmosphere
4. The Hydrosphere
5. Human Activity
• In the past, scientists have had great difficulty
understanding and predicting changes in
climate.
• Recently though, reliable evidence has
emerged on how subsystems interacted and
produced past climatic changes.
Using and improving complex climate models
with sophisticated computer programs,
scientists have been able to simulate
weather and climate. Scientists are now able
to predict climate changes that could follow
from human actions.
Human Activities and The Greenhouse
Effect
• Over the past century major changes have
occurred in agriculture, manufacturing and
transportation, most notably since the middle
of the 19th century and the Industrial
Revolution.
• One major change is the replacement of
organic fuels such as wood, with fossil fuels
such as coal and oil.
Burning of Fossil Fuels
• With the exception of water vapour, the
concentration of greenhouse gases has
steadily been increasing.
– The concentration of carbon dioxide (CO2) in the
atmosphere has been increasing rapidly since the
Industrial Revolution as we have burnt more fossil
fuels.
• To check whether this might simply be a
coincidence, scientists have examined the long
term geological record to see whether the
increase in CO2 over the last two centuries is
normal or unusual.
Ice Cores
• Ice cores taken from Antarctica and the Arctic
indicate that the concentrations of CO2 have
risen at a rate that has no precedent in the
geological record. There are no known natural
processes that would create such a large
increase in CO2.
• Scientists have concluded that human
activities are the main cause of the increase in
CO2 in the atmosphere.
• In addition to burning fossil fuels, clearing of
forests and releasing industrial gases such as
refrigerants, have also contributed to the
enhanced greenhouse effect.
Tree Rings and Global Warming
• A continuous record has been established by
examining tree rings.
• Rings in wood reflect the changing seasons of
cold and drought, warmth and precipitation
during the life of a tree.
• By examining wood from trees of different ages
and from different time periods, a continuous
record of climate changes can be established that
goes back a few thousand years.
More on Greenhouse Gases
• Another of the main greenhouse gases is
methane (CH4), which is 25 times more
effective a greenhouse gas than CO2. This
means that although methane is less
abundant than CO2, its presence has a major
impact on heat absorption in the atmosphere.
• In other words, even though most of the
blanket surrounding the Earth is made of CO2,
the part made of methane is a bit like pure
wool, it keeps you very warm.
Methane
• Methane is generated by the bacterial decay
of dead plant and animal material (including
in waste landfills).
• It is also produced by livestock farming (due to
fermentation processes in the gut of cattle).
• Rice cultivation produces methane.
• Methane can also be found in leakage from
fossil fuel production processes such as coal
mining and natural gas distribution.
• Unstable and collapsing
ice sheets allowed
frozen pockets of
methane to erupt to
the surface.
Methane belching out from beneath ice sheets
• Some scientists believe
that methane is a far
more damaging
greenhouse gas than
carbon dioxide!
• The analysis of ice cores indicates that
changes in methane concentrations in the
atmosphere over time coincide with rises in
the human population.
• This suggests that human activities associated
with urbanization, industry and agriculture are
all significant factors in methane production,
and hence climate change.
Ozone Layer
• Ultraviolet radiation is a part of the solar
radiation spectrum. It causes sun-burn and is
deadly to living organisms, including humans.
• Ozone can absorb the most lethal type of
ultraviolet rays and is therefore crucial to life
on Earth.
• Since 1980, the ozone in the atmosphere has
been depleting because of pollutants emitted
by human manufacture.
• The issue of ozone depletion is an entirely
different process to the greenhouse effect.
• The two are commonly confused, but they
are, simply, two destructive processes
occurring in the atmosphere in response to
human activities.