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CLIMATE
Unit 6
LEARNING OBJECTIVES
1. Compare Weather and Climate
2. Explain major climate categories through the Koppen Climate
Classification systems
3. Summarize natural processes that have affected global
climate
4. Explain the concept of the greenhouse effect, how
deforestation and burning of fossil fuels can contribute to
global climate change and actions that can be taken by
humans to mitigate global climate change
5. Analyze how changes in global temperature can affect the
biosphere, contribute to ocean acidification and impacts sea
level
What is Climate?
Climatology
Climatology is the study of Earth’s climate and the factors that
affect past, present, and future climatic changes
 Pertains to long-term weather patterns of an area
 More than average weather conditions
 Describes annual variations of temperature, precipitation, wind,
and other variables
 Details extreme fluctuations in these variables over time
Normals
 Data used to describe an area’s climate are compiled from
meteorological records from thousands of locations around the
world.
 Data includes daily high and low temperatures, amounts of
rainfall, wind speeds and direction, humidity, and air pressure.
 Once gathered, data is averaged on a monthly or annual basis
over a period of at least 30 years to determine the standard
values (normals) for a location.
Factors that Influence Climate
Latitude
 Based on solar radiation and how the
Sun’s rays strike the Earth
 The tropics refers to the area between
23.5oS and 23.5oN of the equator
 Receives the most solar radiation
 Temperatures are warm year-round
 The temperate zones lie between 23.5o
and 66.5o N and S of the equator
 Temperatures are moderate
 The polar zones lie from 66.5o north and
south of the equator to the poles
 Solar radiation strikes at a low angle
 Temperatures are almost always cold
Topographic Effects
 Water heats and cools more slowly
than land
 Coastal regions are warmer in winter
and cooler in the summer months
 Temperatures in troposphere decrease
with altitude, so mountain climates are
typically cooler than sea level
 In addition, climates differ on each
side of the mountain due to the
rising and sinking of air
Air Masses
 Distinct origin due to difference in solar radiation
 Depends on where formed (land or water)
Climate Classification
Koeppen Classification System
Russian-born German climatologist Wladimir Koeppen (18461940) developed this system based on average monthly values ,
taking into account distinct vegetation that is found in each of
the different climates.
There are a total of 5 main climatic zones.
Climates are classified according to temperature and
precipitation.
Major Climate Zones
1.
Tropical Moist Climates
2. Dry Climates
3. Moist Mid-Latitude with Mild
Winters (Moist Sub-Tropical)
4. Moist Mid-Latitude with Cold
Winters (Moist Continental)
5. Polar Climates
Major: Tropical Moist Climates
Tropical Moist Climates extend northward and
southward from the equator about 15°-25°
All months have an average daily temperature
greater than 64.4°F
Annual precipitation readings are greater than
59”
Three sub-climates exist, based on seasonal
precipitation readings
1. Tropical Wet (Brazil, Congo, Indonesia)
2. Tropical Monsoon (South/Southeastern
parts of Asia)
3. Tropical Wet and Dry (Africa, Brazil, India)
Major: Dry Climates
Most obvious climatic feature of dry climates is
the rate of evaporation and transpiration
exceeds the rate of precipitation
Dry climate zones cover approximately 26% of
the world
Dry climates extend from 20°-35° North and
South of the equator, due to a pattern of
cold water currents forcing dry air over the
lands
Also found on large continental regions that are
surrounded by mountains (due to rain
shadows) in mid-latitude climates
Two sub-climates exist:
1.
Dry Arid (Sahara, Gobi, Atacama Deserts)
2. Dry Semi-Arid (The Outback, Kazahkstan,
and parts of southern Texas)
Major: Moist Subtropical MidLatitude (Mild Winters)
Generally have warm and humid summers
and mild winters
Located on the eastern and western
regions of most continents, between
30°-50° north and south of the equator
The main weather feature is the midlatitude cyclone (hurricane) and
convective thunderstorms
Three sub-climates exist:
1. Humid Sub-Tropical (SE USA)
2. Mediterranean (Northern CA,
Mediterranean Basin countries)
3. Marine (Pacific NW, Western Europe)
Major: Moist Mid-Latitude with Cold
Winters (Moist Continental)
 Warm to cool summers, cold winters with
massive conflict between polar and tropical
air masses
 Large, seasonal temperature contrasts
 Found only in the northern hemisphere,
from 40°-70° north of the equator
 Average temperature of warmest month is
greater than 50°F and coolest temperature
is 26°F
 Winters are severe, with snowstorms,
strong winds, and bitter cold
 Three sub-climates exist:
1.
Dry Winter
2. Dry Summer
3. Wet All Season
Major: Polar
Climates
 Year round cold temperatures, with
warmest months being less than 50
degrees
 Doesn’t really experience summer
 Low amount of precipitation
 Found on the northern coastal areas
of North America, Europe, Asia and
the landmasses of Greenland and
Antarctica
 Two sub-climates exist:
1.
2.
Polar Tundra (N Canada, Siberia)
Polar Ice-Caps (Greenland,
Antarctica, North Pole)
Microclimates
 Sometimes, the climate of a small area
can be much different from that of the
larger surrounding area.
 A localized climate that differs from the
surrounding regional climate is called a
microclimate
 In mountainous areas, the climate
becomes cooler with elevation
 In an urban area, the climate is warmer
due to large areas of asphalt and
concrete buildings.
Highlands
 Climate of “high land,” so it’s found
in mountainous areas and mountain
peaks
 No classified seasons, temperatures
range with level of elevation so the
only seasonal differentiation would
be felt at lower elevations
 Temperatures drop approximately 3°
every 1000’ in elevation so at the
base of the mountain it could be
sunny, as you move upward it could
change to rain and then eventually
snow
 Precipitation depends on the
elevation as mountains force warm
air to rise, where it then cools and
creates precipitation
Heat Island
Area where the climate is warmer than in
surrounding rural areas
Large areas of asphalt and concrete radiate
far more heat into the air than grasslands,
wooded areas, and bodies of water
This causes greater changes in temperature
with altitude, which causes convection
currents that produce increased cloudiness
and up to 15% more precipitation in cities
Heat Islands are examples of climatic
change on a small scale and can lead to
urban dust domes
Urban Dust Dome
An urban heat island causes a city to
heat up, capping pollutants into a
“dome” in the lower levels of the
atmosphere
If wind is not strong enough to “blow”
the dome away from the city,
pollutants such as soot, dust, and
chemical emissions become trapped in
a dome over the city
Ultimately, pollutants can possibly
become 1000 times more
concentrated than found in a nearby
rural area
Forests
Forests provide a shaded canopy,
which alters the amount of direct
sunlight received within the
forested area.
By altering the amount of sunlight,
the rate of evaporation is also
altered. In addition to this,
increased vegetation allows for
more infiltration, which ultimately
leads to less evaporation due to a
lack of standing water within the
forested area
These factors ultimately affect the
climate, making it cooler than
surrounding non-forested areas.
Lake Effect (Snow)
 Snow forms in the winter when cold air
masses move over warmer lake waters. The
warm lake water heats the bottom layer of
the air, causing lake moisture to evaporate
into the cold air mass.
 As warm air is less dense, it rises, expands
and begins to cool. The hydrological cycle
then takes over, with the moisture in the air
condensing into clouds. The snow clouds
grow quite large, covering heavy bands 20 to
30 miles wide and over 100 miles inland from
the shore. Once they become saturated, they
precipitate. They could drop snow at rates
exceeding 5 inches per hour!!
 Lake-effect snows are most common in the
Great Lakes region, but can also be found
near any large body of water that remains
free of ice. The Great Salt Lake in Utah and
different bays throughout North America will
occasionally produce bay-effect snow.
Climatic Changes
The Earth’s climate is in a constant state of change
Changes take place over both long and short periods of time.
Geologic records show Earth was once colder or warmer than it is today.
Long-Term Climate Changes
Short-Term Climate Changes
Ice Age
 Period of time where much of Earth
was covered by sheets of ice
 The average global temperature
decreased by an estimated 5o
 Snowfalls increased throughout
Earth, which sparked the advance of
existing ice sheets
 Ice ages alternate with warm periods
(interglacial intervals) in which we are
currently experiencing
 The most recent ice age ended only
10,000 years ago
Seasons
 Short-term periods caused by regular
variations in daylight, temperature,
and weather patterns
 During summer in the Northern
Hemisphere, the North Pole is tilted
toward Sun
 During winter in the Northern
Hemisphere, the North Pole is tilted
away from Sun
 The opposite is true of the Southern
Hemisphere
El Niňo – Southern Oscillation
(ENSO)
 Unusually warm ocean temperatures in the equatorial Pacific, leading to a variation in regional
climatic patterns
 Effects are noticed in the northern hemisphere winter and southern hemisphere summer
 Brings wet weather to areas that are normally dry (excessive flooding) – like the southern tier
of the United States
 Brings dry conditions to areas that are normally wet (extreme drought) – increasing brush fires
in areas like Australia
 Increased ocean warmth enhances convection, which ultimately alters the jet stream and leads
to increased precipitation and cooler than normal winter temperatures
 During hurricane season (June to November), the jet stream becomes aligned in such a way that
the vertical wind shear is increased over the Caribbean and Atlantic – which helps prevent
tropical disturbances from developing into hurricanes
La Niňa – Southern Oscillation
 Unusually cool ocean temperatures in the equatorial Pacific, leading
to a variation in regional climatic patterns
 Stronger low-level atmospheric winds across the equator
 Decreased convection suppresses the jet stream and results in lower
precipitation and warmer than normal winter temperatures in the
southeast and cooler than normal temperatures in the northwest
 During hurricane season (June to November) upper level winds are
lighter and more favorable for hurricane development in the
Caribbean and Atlantic
Why does Climate Change Occur?
Earth’s temperature is a balancing act between energy entering and leaving the surface
 When energy from the Sun is absorbed by Earth, it warms
 When energy from the Sun is reflected back into space, it cools
Many factors, both natural and human induced, result in a change of Earth’s energy balance.
Natural Causes
1.
2.
3.
4.
The Great Ocean Conveyor
Volcanism
Change in Earth’s orbit
Changes in solar activity
Human Factors
1.
2.
3.
4.
Greenhouse Effect
Greenhouse Gases
Aerosols
 Black Carbon
 Sulfates
Deforestation
Changes in Solar Activity
Changes in Earth’s Orbit
 Changes in the shape of Earth’s
orbit, as well as the tilt and
position of Earth’s axis, can affect
the amount of sunlight reaching
Earth’s surface
 These changes in turn affect the
Earth’s temperature on a relatively
long and cannot explain the recent
warming
 Changes occurring in the sun itself can
affect the intensity of the sunlight
 The intensity of the sunlight can cause
either warming (during periods of stronger
solar intensity) or cooling (during periods
of weaker solar intensity)
 The sun follows a natural 11-year cycle of
small ups and downs in intensity; however,
solar activity has been relatively constant
since the mid-20th century
 Changes in solar energy continue to affect
climate, although the effect is small
The Human Factor
The Greenhouse Effect
The Earth balance of its energy retention of heat by the
atmosphere results in the Greenhouse Effect, which is
the natural heating of the Earth’s surface caused by
greenhouse gases.
Without the Greenhouse Effect, life as we know it would
NOT exist on Earth as our planet would be super cold!
Meaning, we could not sustain life without it.
On the other hand, an increase in the greenhouse effect
could cause our planet to be hot.
Scientists believe that it may be possible to increase or
decrease the greenhouse effect by changing the
amount of atmospheric gases… specifically carbon
dioxide
Any Increase in the amount of these gases could result
in the increased absorption of radiation.
Currently, levels of carbon dioxide in the atmosphere
ARE increasing – which can lead to a rise in global
temperatures.
Greenhouse Gases
The primary human activity
causing a rise in greenhouse
gases includes the burning of
fossil fuels
As these gases are released into
the Earth’s atmosphere they
trap the heat close to the
Earth’s surface, leading to an
increase in surface
temperature and the natural
balancing of the Earth to be
offset
The most important greenhouse
gases emitted by humans
include carbon dioxide,
methane, nitrous oxide, and
chlorofluorocarbons (CFC’s)
Greenhouse Gases – Carbon Dioxide
Carbon dioxide is the primary
greenhouse gas that is
contributing to the recent
climatic changes
Carbon dioxide is absorbed and
emitted naturally through the
carbon cycle by way of plant and
animal respiration, volcanic
eruptions, and ocean –
atmosphere exchanges
Human activities currently release
over 30 billion tons of carbon
dioxide per year
* Carbon Bathtub Analogy *
Deforestation
 Forests play a massive role in the
Earth’s carbon cycle, as they are able
to store up to 100 times more carbon
than agricultural fields of the same
area
 When forests are cut down, carbon
absorption ceases and carbon being
stored in trees is released into the
atmosphere as CO2 regardless of
whether or not the wood is burned or
left to rot
 It is estimated that more than 1.5
billion tons of carbon dioxide are
released into the atmosphere due to
deforestation
Greenhouse Gases - Methane
The concentration of methane in the atmosphere has more than
doubled in the past 200 years, contributing to approximately 12-20% of
the greenhouse effect. (In recent years the emission of methane has
decreased nearly 15% although the long term effects are still being
seen through global warming)
Methane is produced through both natural and human activities.
 Termites produce methane as they process wood
 Freshwater wetlands produce methane through decomposing plants
in oxygen poor environments
 Seepage from oil fields
 Seepage from landfills, burning biomass, production of coal and
natural gas, and agricultural activities
Greenhouse Gases – Nitrous Oxide
Nitrous oxide accounts for about 5% of the greenhouse effect
It is currently increasing in the atmosphere due to agricultural
activities (application of fertilizers) and the burning of fossil
fuels
Reducing the use of fertilizers and burning of fossil fuels would
reduce emissions; however, the long residence time (114 years)
of this gas would account for elevated concentrations for
several decades
Greenhouse Gases - Aerosols
Chlorofluorocarbons (CFC’s) are inert, stable compounds that
have been or are being used in spray cans as aerosol
propellants and in refrigeration units.
Use of CFC’s was banned in the USA in 1978; however, many
countries have no ban on aerosols.
Deliberate release and accidental leaks of CFC into the
atmosphere have been considerable, with the rate of increase
about 5% per year. As result, it is estimated that 15-25% of the
greenhouse effect may be related to CFC’s.
The Montreal Protocol of 1987
A treaty designed to reduce and
eventually eliminate the production of
CFC’s and to accelerate the
development of alternative chemicals.
Production of CFC’s was nearly phased
out by 2000; however, as not every
country signed the treaty production
continues in some countries.
Without the Montreal Protocol regulating
CFC’s, they would have become the
major contributor to the greenhouse
effect.
Global Warming
Global warming a natural or human-induced increase in the average global temperature of
the atmosphere near the Earth’s surface.
The temperature at or near the surface of the Earth is determined by four main factors:
1.
The amount of sunlight Earth receives
2. The amount of sunlight Earth reflects
3. Retention of heat by the atmosphere
4. Evaporation and condensation of water vapor
Over past 200 years, temperatures have increased globally, with the warmest years on record
having occurred over the past two decades (20 years).
If this continues polar ice caps might melt and sea levels will rise, leading to flooding.
Global warming can also cause an increase in the frequency of severe storms.
Impacts of Global Warming
Monsoons and Climate Change
 Overall, global warming will change conditions in the sea more
slowly than conditions on land because of the differences in the
heating (sea breeze)
 As result, summer monsoons are amplified by stronger warming
in summer. With more moisture in the air, rainfall and flooding
might be expected to increase.
 In winter there is less difference as the land doesn’t get quite as
cold, so winter monsoons weaken
El Nino and Global Warming
 El Niño events are not new (evidence suggests they have been
occurring for hundreds of years) and generally have occurred once
every 5 years
 As climatic changes occur, it is predicted that the likelihood of El Niño
will occur once every three years
 We have noticed a warming of the tropical Pacific, with greater
warming in the east than in the west. This pattern is typically
associated with El Niño and could show an increase in El Niño severity.
 If the current El Niño trend continues, consequences could take a
heavy toll on the entire world
 U.S. insurance industry (severe storms)
 Worldwide sustainable developments
Polar Amplification
 As temperatures increase
through global warming, we
see the most significant
changes in the polar regions
 Sea ice melts from higher
temperatures
 Water reflects less light than
ice, causing advanced warming
as solar energy that would
have been reflected by the ice
is absorbed by the ice free
water
Hudson Bay Polar Bears Study
Global Warming issues in the biosphere
As the surface temperature of Earth is increasing, sea ice is melting earlier
throughout the year and at more alarming rates
To monitor the effects of global warming on attaining sustainable developments,
the polar bears of Hudson Bay are being studied
 Sea ice is thinning as much as 40% and decreasing in extent by a rate of 10%
 Sea ice is a critical habitat for hunting seals
 In spring, polar bears prey on young seals, allowing the bears to fatten up prior to the
annual melting of the sea ice
 After the ice melts, the bears move onto land and fast for months
 Pregnant bears fast 8 months (so they require significant fat to raise their cubs until
they can again eat
 Since the start of the Hudson Bay study (1981) bears have weighed less than average
and given birth to fewer cubs
 As the sea ice breaks up earlier, numbers continue to decline
 Decline is leading to bears moving onto land earlier, where dangerous encounters are
occurring with humans
Additional Effects of Global Warming
Although it is nearly impossible to predict, global warming could
have the following consequences:
1.
2.
3.
4.
5.
6.
Semi-arid areas will become drier, other regions will become
wetter
World distribution of biomes will likely change (tundra could be
lost while deserts may expand)
Incidence of diseases will increase in tropical countries (malaria)
Agricultural production in some regions will decrease
Rising sea levels will accompany coastal erosion
Biosphere will change as result of damage to ecosystems (coral
reefs / arctic areas
Protecting our Planet
Impact of Human Activities
• Automobiles serve as the prime source of atmospheric CO2
• Burning of fossil fuels results in the release of CO2 and other gases into
atmosphere
• Deforestation is the massive removal of trees, which increases the CO2 into
atmosphere because vegetation removes carbon dioxide during
photosynthesis
Environmental Efforts
• We can conserve energy, as individuals, to combat global warming
• Conservation of energy helps reduce the consumption of fossil fuels
• Easy ways to conserve energy include:
•
•
•
•
Turning off appliances and lights
Turning down thermostats during the winter
Recycling
Riding bikes for transportation… or walking