Download how the atmosphere affects climate

CHAPTER 7: EARTH’S CLIMATE SYSTEM
FACTORS THAT AFFECT CLIMATE CHANGE

ATMOSPHERE is a layer of gases that surrounds a planet or moon.
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Without our atmosphere, Earth would experience scorching hot days, and freezing cold
nights.

WEATHER is the condition of the atmosphere in a specific place at a specific time.
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Weather describes factors such as wind, temperature, and the amount of moisture in the
atmosphere.
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In Canada, we experience patterns of weather in the cycle of seasons (hot summers and
cold winters).
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Countries close to the equator, do not experience cold winters, but tend to have cycles of
wet seasons and dry seasons.

CLIMATE is the average conditions of the atmosphere over a period of several years over a
large region.
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Climates around the world have changed many times over the Earth’s history (millions of
years). For example, thousands of years ago, thick ice sheets covered most of Canada and
most of the United States.
EARTH AND THE SUN

Energy from the Sun is the single most important factor that affects climate on Earth.

Solar energy travels through space as light and heat. The intensity of this solar energy affects
the temperature of the air, water, and land, once it hits Earth’s surface. This heat produces
winds, rain, and other features of the climate.

The amount of solar energy depends on the shape of the planet and on Earth’s angle of tilt and
orbit around the Sun.

Earth rotates (spins) once every 24 hours around its axis (an imaginary line running from the
North Pole to the South Pole). While continuously rotating on its axis, Earth makes a year-long
journey around the Sun. Throughout this path (or orbit), Earth remains in the same orbital plane.

Earth’s axis of rotation is tilted at an angle of approximately 23.5 degrees from a line
perpendicular to the orbital plane.

The combination of Earth’s annual orbit around the Sun, and its tilted axis, produces our seasons.

Latitude also affects how much of the Sun’s rays will hit a specific part of Earth. For example,
countries closer to the equator are closer to the Sun (therefore, have shorter distances for the
Sun’s rays to travel). This more direct contact from the Sun’s rays means that the overall
temperatures will be warmer. In Canada, the Sun’s rays must travel further, therefore spread
out more. This means that each square metre of land receives less solar energy.
HOW THE ATMOSPHERE AFFECTS CLIMATE

The atmosphere extends from Earth’s surface up to approximately 560 km into space.

It is composed mainly of nitrogen gas (N2), and oxygen gas (O2), as well as water vapour (H2O).
There are a very small concentration of other gases and particles of solids.

GREENHOUSE EFFECT is the natural warming caused when gases in Earth’s atmosphere
absorb thermal energy that is radiated by the Sun and Earth.
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This process helps to keep Earth’s temperature fluctuations within a certain range.
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Without this process, most of the solar energy reaching Earth would radiated back into
space and the average temperature at the planet’s surface would be 34°C lower than it is
today.

WIND is the movement of air from an area of high pressure to an area of lower pressure.
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All winds begin as a result of uneven heating of Earth’s surface.
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This movement of air as wind transfers thermal energy around the world from warm areas
to cooler areas.
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The movement of air affects ocean currents and precipitation patterns.
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Because the oceans absorb energy from the Sun, the movement of the water results in the
transfer of heat around the Earth’s surface.
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Winds blow in fairly constant directions around the world. These air currents are known
as “prevailing winds”.
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As air masses of different densities move across Earth’s surface, they interact. When air
masses meet, one air mass usually rises over the other. The rising air cools, and any water
vapour in the air condenses to form precipitation.
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Winds also affect precipitation through jet streams. Jet streams are high-altitude
winds that travel long distances at very high speeds. These winds may carry warm, moist
air, which can produce precipitation in areas far from the origin of the jet stream. They
may also carry dry, cool air, which causes dry weather in areas affected by jet streams.
Canada’s weather is particularly influenced by the polar jet stream.

Seen from space, Earth is a blue planet. Oceans cover about 2/3 of Earth’s surface.

All the water in its different forms on Earth composed the HYDROSPHERE. Together with the
atmosphere, water transfers heat from one part of the planet to another.

The oceans can hold much more heat than the atmosphere can. The top 2.3 metres of the world’s
oceans hold as much heat as all of the planet’s air does. As a result, the oceans act as a “heat
reservoir” that buffers temperature changes in the atmosphere. Since water has a large specific
heat capacity, a large quantity of energy is required to raise its temperature compared with the
energy needed to change the temperature of land. As a result, the temperature of large bodies
of water tends to change slowly and by small amounts.

Because of their light colour, snow and ice reflect solar radiation. The fraction of energy that is
reflected by a surface is known as ALBEDO.
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The amount of energy reflected or absorbed depends largely on the colour of the surface.
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In general, light-coloured surfaces reflect energy, and dark-coloured surfaces absorb
energy.
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This is why it is hard to see when a surface is icy (the white surface reflects so much of
the Sun’s rays).
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This is also why roads (black tar) get so hot in the summer (the black surface absorbs so
much of the Sun’s rays).
HOW HUMAN ACTIVITY AFFECTS CLIMATE

There is growing evidence that the present change in climate (since the 1970’s) is at least partly
ANTHROPOGENIC (caused by humans).
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The main link is the effect human technology has on the atmosphere.
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For many centuries, a major source of energy used by people has been the burning of fossil
fuels (coal, oil, and natural gas).
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The Industrial Revolution of the late 1700’s was the beginning of the burning of fossil
fuels (as cars and manufacturing plants were invented).
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Now, the usage of trains, automobiles, ships, factories, aircrafts, farming and mining
equipment, home furnaces, and electricity generating stations are just some examples of
technologies that use fossil fuels.
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When these fuels are burned to release energy, they release gases and other pollutants
into the atmosphere as waste products.
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As humans have increased their usage of fossil fuels, the concentration of these gases in
the atmosphere has increased.
DESCRIBING CLIMATES

Aristotle classified 3 major climate zones on the planet. These climate zones were based on
their increasing distance from the equator.
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The centre of the planet, between the Tropic of Cancer (approximately 23° north of the
equator) and the Tropic of Capricorn (approximately 23° south of the equator) is
classified as the tropical zone.
 In the tropical zone, temperature is relatively warm and varies little throughout the
year.
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The area between the North Pole (approximately 66° north of the equator – called the
Arctic Circle) and the South Pole (approximately 66° south of the equator) is classified as
the Polar Zones.
 Polar zones are characterized by cold temperatures and by ice cover for much, or all,
of the year.
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Between the polar and tropical zones lie the temperate zones.
 In the temperate regions, temperature may vary greatly during the year, and many
regions experience distinctly warm and cold seasons.

CLIMATOGRAPH 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.
INDICATORS AND EFFECTS OF CLIMATE CHANGE

The largest single indicator of climate change has been GLOBAL WARMING – the increase in
the average temperature of the atmosphere and oceans.
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The rate of increase has accelerated since the 1960’s.
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This warming is an average for the entire planet, which means that some regions of Earth
have experienced more warming than others, and some have actually grown cooler during
this period.

Changes in Polar and Glacial Ice:
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Large volumes of ice in Greenland and the Antarctic have been melting at higher rates in
recent years. For example, the overall loss of mass in the West Antarctic ice sheet has
been approximately 65 km3 per year. This amount of melting releases enough water to
raise the sea levels by about 0.16 mm per year.
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Melting ice not only raises the sea levels, it also affects the habitat of animals such as
seals and polar bears. Polar bears now have to range further away to find food, and are
starving.

Rising Sea Level and Ocean Acidity:
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The average sea level has risen between 10-15 cm over the past 100 years.
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Scientists believe that the continued melting of ice in glaciers and icecaps outside of
Greenland and Antarctica, including the approximately 150 000 km2 of ice in Canada, could
cause global sea levels to rise by 20 to 40 cm within the next 100 years.
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These rising sea levels mean that many areas on coastlines will be submerged in water.
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As parts of the world’s oceans become warmer, changes in ocean pH and in sea level pH
have occurred. Research indicates that between 1751 and 2004, surface ocean pH
dropped from approximately 8.25 to 8.14.
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This drop in pH (which means that the ocean is more acidic) means that coral reefs are
now poorly formed and not as stable (since they are high in carbon dioxide and the oceans
now have less dissolved carbon dioxide).
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
This increase in acidity will also affect the ability of fish and plankton to reproduce.
Climate and Health:
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Climate is closely connected with health – the risk of disease and infection, as well as the
risk of injury or death due to extreme weather (heat waves, floods, tornadoes, or
snowstorms).
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With climate changes have come outbreaks of infections such as lyme disease, malaria and
the plague. Waterborne diseases have also increased.
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Increasing temperatures affect the amount of dust in the air, the growth of mould, and
the release of pollen by many plants. This increases the number of people affected by
allergies, as well as increasing the intensity of these allergies.
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As well, increased temperatures contribute to the number of smog days in the summer
months. This can have detrimental concerns for people with respiratory problems.

Changing Wind and Precipitation Patterns:
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Changes in heat distribution over Earth’s surface have led to changes in wind patterns.
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The speed, frequency, and direction of winds over Earth’s surface, have fluctuated
unpredictably for several years.
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It is believed that these unpredictable wind patterns have contributed to the increase in
the melting of the ice in the Arctic.
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High temperatures increase the rate of evaporation. When warm, moist air rises and cools
the upper atmosphere, it produces rain or snow.
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Since 1948, average annual temperatures across Ontario have increased by as much as
1.4°C. Average precipitation has also increased over this period.
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As average temperature increases, so does a decline in precipitation in certain areas
(farming areas). It can lead to DESERTIFICATION which is the process by which land
slowly dries out until little or no vegetation can survive and the land becomes a desert.

Deforestation:
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DEFORESTATION is the removal of trees and forests from an area through human
activity (logging, slash and burn clearing).
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A shrinking forest area reduces the amount of carbon dioxide (CO2) absorbed from the
atmosphere by photosynthesis. Therefore, there is more carbon dioxide in the
atmosphere.

Shrinking Wetlands:
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Freshwater ecosystems plan an important role in regulating climate, as well as supplying
water for human needs.
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Wetlands include marshes, bogs, and swamps. These ecosystems store and filter water.
They are also habitats for plants that remove carbon dioxide from the air; and a variety of
animals.
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Lower water levels in the Great Lakes will dry out wetlands around the shorelines, reducing
the habitat for wetland species of plants and animals.