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Unit 6: Atmosphere Notes
Part 3: Chapter 17: Climate
17.1: Climate and Its Cause
Lesson Objective
 Describe the effect of latitude on
climate.
 Diagram the Hadley, Ferrell, and
Polar atmospheric circulation cells
and show how they influence the
climate of various locations.
 Discuss the other important
location factors that influence a
locations’ climate: position in the
global wind belts, proximity to a
larger water body, position
relative to a mountain range, and
others.
Vocabulary
 Continental Climate
 Intertropical Convergent Zone
(ITCZ)
 Maritime Climate
Introduction
 Although almost anything can happen with the
weather, climate is more predictable.
 Climate then is the long-term average of weather.
 Good climate is why we choose to vacation in Hawaii in
February, even though the weather is not guaranteed to
be good.
What is Climate?
 The average of weather in that location over a period of
time, usually for at least 30 years.
 A location’s climate can be described by its:
 Air temperature, humidity, wind speed and direction
 The type, quantity, and frequency of precipitation
 Climate can change, but only over long periods of time.
 The climate of a region depends on its position relative to
many things.
Latitude
 The main factor
influencing the climate of
a region - because
different latitudes receive
different amounts of solar
radiation.
 The equator receives the
most solar radiation
 The polar regions
receive the least solar
radiation
Atmospheric Circulation Cells
 The position of a region
relative to the circulation
cells and wind belts has a
great effect on climate.
The ITCZ (Intertropical Convergence
Zone)
 The low pressure area
near the equator in the
boundary between the
two Hadley Cells
Cell Boundary
 Hadley Cell and Ferrell
Cell Boundary
 At this location the air is
descending, and
shrinking air warms and
causes evaporation.
 Ferrell Cell and Polar Cell
Boundary
 The meeting of the two
different air masses
causes the polar jet
stream, which is known
for its stormy weather.
Prevailing Winds
 The bases of the Hadley,
Ferrell, and Polar Cells.
 Bring weather from the
locations they come
from.
Continental Position
 When a particular location is near an ocean or large
lake, the body of water plays an extremely important
role in affecting the regions’ climate.
 Maritime climate is strongly influenced by the nearby sea
Temperatures vary a relatively small amount seasonally and
daily
 Continental Climate – more extreme
 With greater temperature differences between day and
night and between summer and winter
Ocean Currents
 The temperature of the
water offshore influences
the temperature of a
coastal location,
particularly if the winds
come off the sea.
 Coastal upwelling also
brings cold, deep water up
to the ocean surface off of
California, which
contributes to the cool
coastal temperatures.
Altitude and Mountain Ranges
 Air pressure and air temperature decrease with altitude.
 The closer molecules are packed together, the more likely
they are to collide.
 Collisions between molecules give off heat, which warms the air.
 Mountain ranges have two effects on the climate of the
surrounding region:
 Rainshadow Effect – which brings warm dry climate to the
leeward side of a mountain range
 Separation of the coastal region from the rest of the continent.
17.3: Climate Change
Lesson Objective
 Describe some ways that climate
change has been an important
part of Earth’s history.
 Discuss what factors can cause
climate to change and which of
these can be exacerbated by
human activities.
 Discuss the consequences of rising
greenhouse gas levels in the
atmosphere, the impacts that are
already being measured, and the
impacts that are likely to occur in
the future.
Vocabulary
 El Nino
 Global Warming
 La Nina
 Milankovitch Cycles
 Slash-and-burn Agriculture
 Sunspots
Introduction
 For the past two centuries, climate has been relatively
stable.
 People placed their farms and cities in location that
were in a favorable climate without thinking that the
climate could change.
 But climate has changed throughout Earth’s history, and
a stable climate is not the norm.
 Stability has allowed the expansion of agriculture and the
development of towns and cities.
Short – Term Climate Change
 Are common – the largest and most important of these is
the oscillation between El Nino and La Nina conditions
 The cycle is called the ENSO (El Nino Southern
Oscillation)
 The ENSO drives changes in climate that are felt around
the world about every two to seven years
 In a normal year, the trade winds blow across the Pacific
Ocean near the equator from east to west (towards
Asia)
 In an El Nino year, when water temperatures reaches
about 820F, the trade winds weaken or reverse direction
and blow east (towards South America)
 Upwelling stops
 By altering atmospheric and oceanic circulation, El Nino events
change global climate patterns.
 Some regions receive more than average rainfall, including the west
coast of North and South American, the southern US and Western
Europe
 Drought occurs in other parts of S. America, the western Pacific,
southern and northern Africa, and southern Europe.
 An El Nino cycle last one to two years – sometimes circulation
patterns bounce back quickly and extremely – this is called a La
Nina
 In a La Nina year, as in a normal year, trade winds moves from east
to west and warm water piles up in the western Pacific Ocean.
 Ocean temperatures along coastal S. America are colder than
normal (instead of warmer like in El Nino)
 Cold waters reach farther into the western Pacific than normal
Causes of Long-term Climate Change
 Many processes can cause climate to change. These
include changes:
 In the amount of energy the Sun produces over years
 In the positions of the continents over millions of years
 In the tilt of Earth’s axis and orbit over thousands of years.
 That are sudden and dramatic because of random
catastrophic events, such as a large asteroid impact
 In greenhouse gases in the atmosphere, caused naturally
or by human activites.
Causes of Long-term Climate Change
 Solar Radiation
 The amount of energy
the Sun radiates is
variable
 Plate Tectonics
 Can alter climates
 Over millions of years as seas open and
close, ocean currents may distribute
heat differently
 When the continents separate, heat is
more evenly distributed.
 Triggers volcanic eruptions, which
release dust and CO2 into the
atmosphere.
Milankovitch Cycle
 Scientist attribute a series of ice ages to variation in the
Earth’s position relative to the Sun
 1.) The shape of the Earth’s orbit changes slightly as it goes
around the Sun.
 2.) The planet wobbles on its axis of rotation.
 The planet’s tilt on its axis varies between 22.10 and 24.50
Seasons are caused by the tilt of Earth’s axis of rotation
Changes in Atmospheric Greenhouse
Gas Levels
 A decrease in greenhouse gas levels decrease global
temperatures and an increase raises air temperature.
 Natural processes add and remove CO2 from the
atmosphere:
 Add CO2
Volcanic eruptions and decay or burning of organic matter
 Remove CO2
Absorption by plant and animal tissue
 When plants are turned into fossil fuels the CO2 in their tissue is stored with
them.
 So CO2 is removed from the atmosphere
 Fossil fuels use has skyrocketed in the past few decades – this has released
CO2 into the atmosphere
 Burning tropical rainforests, to clear land for agriculture, also increases
atmospheric CO2
 CO2 is the most important greenhouse gas that human activities affect
because it is so abundant.
 Methane
 Chlorofluorocarbons (CFCs) – human-made chemicals
 Tropospheric Ozone – from vehicle exhaust
Global Warming
 With more greenhouse gases trapping heat, average
global temperatures are rising (aka GLOBAL WARMING)
Temperatures are Rising
 The rate of increase has been more rapid in the past century,
and has risen even faster since 1990.
 The nine warmest years on record have all occurred sine 1998,
and 10 of the 11 warmest years have occurred since 2001
 Annual variations aside, the average global temperature has
increased
 The US has long been the largest emitter of greenhouse gases
 China’s rapid economic growth, its emissions surpassed those of
the US in 2008
 The average US citizen produces far more greenhouse gases
than the average Chinese person
Future Warming
 In the developed nations it will depend on technological
advances or lifestyles changes that decrease emissions.
 In the developing nations, it will depend on how much
their lifestyles improve and how these improvements are
made.
 Computer models are used to predict the effects of
greenhouse gas increase on climate for the planet as a
whole and also for specific regions.
 If nothing is done to control greenhouse gas emissions and
they continue to increase at current rates, the surface
temperature of the Earth can be expected to increase
 Whatever the temperature increase, it will not be
uniform around the globe
 The North Pole has been affected more than the South
Pole
 BUT the temperatures are still increasing in Antartica
 The timing of events for species is changing
 Glaciers are melting and vegetation zones are moving uphill
 As greenhouse gases increase, changes will be more extreme.
 Oceans will become slightly more acidic (making it hard for coral reefs
to grow)
 Decreased snowpacks, shrinking glaciers, and the earlier arrival of
spring will lessen the amount of water available in some regions of the
world
 Weather will become more extreme with heat waves and droughts.
 Although scientists do not all agree, hurricanes are likely
to become more severe and possibly more frequent.
 Sea level is expected to rise
Food For Thought?
 Are the increase in global temperatures natural?
 In other words, can natural variations in temperature account for
the increase in temperature that we see?
 NO! Changes in the Sun’s irradiance, El Nino and La Nina cycles,
natural changes in greenhouse gas, and other atmospheric gases
cannot account for the increase in temperature that has already
happened in the past decade!