1. © 2011 Pearson Education, Inc.
Chapter 8: Climate and
Climate Change
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess

2. © 2011 Pearson Education, Inc.
Climate and Climate Change
2
• Climate Classification
• World Distribution of Major Climate Types
• Global Patterns Idealized
• Global Climate Change

3. © 2011 Pearson Education, Inc.
Climate Classification
• Need a consistent climate
classification scheme to
understand numerous climate
regions
• Earliest known scheme was
by the ancient Greeks 2200
years ago
• Classified three major climate
regions
3
Figure 8-1

4. © 2011 Pearson Education, Inc.
Climate Classification
• Köppen climate classification system
• Based on a database of annual and monthly average
temperature and precipitation
• Four of five major groups classified by temperature
• Fifth group classified by precipitation
• Subdivided the five groups further based on
temperature and precipitation relationships
• Köppen letter code system
– Three letters; first describes group, second describes
precipitation, third describes temperature
• Climographs
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5. © 2011 Pearson Education, Inc.
Climate Classification
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Figure 8-2
• The modified Köppen classification system

6. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
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Figure 8-11
• Weather records. How do we explain their locations?

7. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Tropical Humid Climates
(Group A—Figure 8-5)
– Molded by the tropical
latitudinal regions
– Winterless climates; little
temperature change
– Moisture is prevalent
– Precipitation influenced
by ITCZ
– Three subtypes
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Figure 8-5

8. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Tropical wet climate (Af)
– Equatorial
– Monotonous climate
– Daily temperature range
exceeds annual range
– High humidity
– Rainfall multiple times a
day
– High solar angle year
round; ITCZ influences
rainfall
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Figure 8-6b
Figure 8-6a

9. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Tropical savannah
climate (Aw)
– Lies north and south of
Af climates
– Seasonal alteration of
wet and dry periods due
to position changes of
ITCZ
– Smallest rainfall
amounts of tropical
regions
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Figure 8-8b
Figure 8-8a

10. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Tropical monsoonal
climate (Am)
– Regions with prominent
monsoonal wind pattern
– Extensive rainfall during
high-Sun season
– Cherrapunji, India
averages 425 inches
– Cloud cover reduces
temperatures slightly in
summer versus spring
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Figure 8-10b
Figure 8-10a

11. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Dry climates (Group B –
Figure 8-12)
– Cover about 30% of
land area worldwide
– Lack of uplift or lack of
moisture
– Typical in subtropics
– Marine deserts
– Two main types, two
subtypes
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Figure 8-12

12. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Subtropical desert climate
(BWh)
– Lie near subtropical highs
– Precipitation is scarce
(rare) and unreliable
(highly variable)
– Precipitation that does
form is short lived and
intense
– Hot temperatures
– Large diurnal range of
temperature
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Figure 8-14b
Figure 8-14a

13. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Subtropical steppe climate
(BSh)
– Typically surrounds BWh
climates
– Separate desert climate
from humid climate
– Extremes are muted in
steppe regions
• Cooler temperatures
• More rainfall
– Seasonal concentration
of rainfall
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Figure 8-17

14. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Midlatitude desert climate
(BWk)
– Far removed from oceanic
influence
– Meager and erratic
precipitation
– Most precipitation occurs
in summer
– Cold winters, overall
cooler temperatures
– Greater annual
temperature range
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Figure 8-18a
Figure 8-18b

15. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Midlatitude steppe climate
(BSk)
– Occupies transitions
between desert and
humid climates
– Greater precipitation than
midlatitude deserts
– Less temperature
extremes than midlatitude
deserts
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Figure 8-19

16. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Mild Midlatitude Climates
(Group C—Figure 8-20
– Transition between
warmer tropical climates
and colder severe
midlatitude climates
– Hot summers, mild
winters
– Highly variable
precipitation amounts
– Three primary groups
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Figure 8-20

17. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Mediterranean Climate
(Csa, Csb)
– Modest annual
precipitation in winter,
summer is virtually rainless
– Mild winters and hot
summers
– Clear skies especially in
summer
– Most is Csa (hot
summers); Csb climates
have mild summers and
are more coastal 17
Figure 8-21a
Figure 8-21b

18. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Humid Subtropical Climate
(Cfa, Cwa)
– Warm to hot summers;
high humidity (Cfa days are
hot and sultry)
– Precipitation reaches
summer maximum, some
drop off for winter
– Winter temperatures in Cfa
regions are mild; typically
cooler than mediterranean
climates
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Figure 8-24a
Figure 8-24b

19. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Marine West Coast Climate
(Cfb, Cfc)
– Influenced by onshore flow
from midlatitude westerlies
– Occurs when no topographic
boundaries inhibit flow of
maritime air inland
– Frequently cloudy with
precipitation
– Temperate climate
– Wettest of the midlatitudes
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Figure 8-26a
Figure 8-26b

20. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Severe Midlatitude
Climates (Group D)
– Only in Northern
Hemisphere
– Continentality—
remoteness from oceans
– Four recognizable
seasons; long, cold winter
and short summer
– Subdivided into two types
based on temperature
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Figure 8-27

21. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Humid Continental Climate
(Dfa, Dfb, Dwa, Dwb)
– Dominated by westerlies and
associated frequent weather
changes
– Warm summers, cold winters
– Generally low precipitation;
higher amounts near coasts
– Winter precipitation
associated with cyclones;
summer with convection
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Figure 8-28a
Figure 8-28b

22. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Subarctic Climate (Dfc, Dfd,
Dwc, Dwd)
– Winters are long, dark, and
bitterly cold
– Summers are short; spring
and fall pass quickly
– Coldest temperatures; little
precipitation
– Largest annual temperature
ranges (i.e., -90 °F to 98 °F
in Verhoyansk, Siberia)
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Figure 8-31a
Figure 8-31b

23. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Polar Climates (Group E)
– Receive little insolation
– No average temperature
above 50 °F
– Extremely dry, but
classified as nonarid
– Two primary groups
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Figure 8-27

24. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Tundra Climate (ET)
– Southern boundary the
“treeline”
– Northern boundary border
of any plant cover
– Long, dark winters
– Brief, cool summers
– Little precipitation
– Winters not as severely
cold as subarctic climate
region
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Figure 8-33a
Figure 8-33b

25. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Ice Cap Climate (EF)
– Mainly Greenland and
most of Antarctica
– Permanent cover of ice
and snow
– Ice plateaus; high latitude
with high altitude
– Very limited precipitation,
essentially polar deserts
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Figure 8-34a
Figure 8-34b

26. © 2011 Pearson Education, Inc.
World Distribution of Major
Climate Types
• Highland Climate
(Group H)
– Nearly infinite variations
from place to place
– Altitude more significant
than latitude in highlands
– Exposure (whether a
slope is windward or
leeward)
– High diurnal temperature
variations due to thin, dry
air
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Figure 8-36

27. © 2011 Pearson Education, Inc.
Global Patterns Idealized
• Presumed arrangement of Köppen climate types on a
hypothetical continent (Figure 8-40)
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Figure 8-40

28. © 2011 Pearson Education, Inc.
Global Climate Change
• Changes in climate on long time scales
• Weather is noise, climate is long-term signal
• Episodic events (i.e., El Niño and the PDO) versus
long-term global climate change
• Numerous time scales to consider (i.e., temperature)
– 70 million years, clear global cooling trend
– 150,000 years, temperature fluctuated
– 10,000 years, sharp warmup
– 150 years, warming trend relative to last 1000 years
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29. © 2011 Pearson Education, Inc.
Global Climate Change
• Paleoclimatology
– Proxy measures of
climate (i.e., ice cores,
tree rings)
• Dendrochronology—
study of past climate
through tree ring analysis
• Oxygen isotope analysis
– Lighter versus heavier
isotopes
– High 18
O/16
O ratio,
glaciation
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Figure 8-41

30. © 2011 Pearson Education, Inc.
Global Climate Change
• Coral reefs
– Ratio of 18
O/16
O in coral reefs
– Height of old reefs
• Ice cores
– Ratio of 18
O/16
O serves as a
thermometer
– Provide direct atmospheric
composition measurements
• Pollen data
– Radiocarbon dating
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Figure 8-42

31. © 2011 Pearson Education, Inc.
Global Climate Change
• Causes of Long-Term
Climate Change
– Atmospheric aerosols
• Large quantities of aerosols
can block insolation and lower
temperature
• Result from volcanic
eruptions or asteroid impacts
• Anthropogenic impacts
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Figure 8-43

32. © 2011 Pearson Education, Inc.
Global Climate Change
• Climate change causes (cont.)
– Solar output fluctuations
• Sunspot activity related to solar
output
– Variations in Earth-Sun
relations
• Shape of Earth’s orbit
• Inclination of Earth’s axis
• Precession of Earth’s axis
• Milankovitch cycles
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Figure 8-44

33. © 2011 Pearson Education, Inc.
Global Climate Change
• Climate change causes (cont.)
– Greenhouse gas concentrations
• Greenhouse gas concentrations related to temperature
• Evidence of CO2 increase being anthropogenic
– Feedback mechanisms
• Positive feedback mechanisms
• Water vapor feedback challenges
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34. © 2011 Pearson Education, Inc.
Global Climate Change
• Climate change causes (cont.)
– Roles of the oceans
• Absorb large amounts of carbon
• Methane hydrates
• Heat transfer from low latitudes
to high latitudes
• Climate models
– General circulation models
(GCMs)
– Numerous assumptions
– Accuracy of the models
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Figure 8-45

35. © 2011 Pearson Education, Inc.
Global Climate Change
• Evidence of current global
warming
– 11 of 12 warmest years on
record occurred between 1995–
2006
– Global temperature increasing at
0.13 °C per decade
– Ocean temperatures increasing
to depths of 9800 feet
– Sea level rise
– Temperatures in Arctic increasing
at twice global rate
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Figure 8-46a

36. © 2011 Pearson Education, Inc.
Global Climate Change
• Evidence of current global
warming (cont.)
– Sea ice in Arctic decreasing by
7.4 percent per decade
– Ice caps and glacier melt leading
to sea level rise
– Temperatures on top of a
permafrost layer have increased
by 5.4 °F
– Number of intense tropical
cyclones increased since 1970
– Amount of water vapor in
atmosphere increased
– Changes in precipitation amounts
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Figure 8-46b

37. © 2011 Pearson Education, Inc.
Global Climate Change
• Evidence of current global warming (cont.)
– Concentrations of carbon dioxide correlated with temperature
– Carbon dioxide concentrations correlate with increased
anthropogenic greenhouse gases
– Carbon dioxide increasing at a rate faster than observed in last
800,000 years
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38. © 2011 Pearson Education, Inc.
Global Climate Change
• Consequences of global
warming
– Projected climate in the
upcoming century
• Climate will warm at about 0.4 °F
per decade
• Changes will be greater than
those observed during 20th
century
• Estimated increase of
temperature from 3.3 °F to 7.2 °F
• Sea level rise
• Stronger tropical cyclones
• Increased precipitation
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Figure 8-47a

39. © 2011 Pearson Education, Inc.
Global Climate Change
• Addressing global warming
– Kyoto protocol
– Standards for newly
industrialized countries
– Mitigating and adapting
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Figure 8-47b

40. © 2011 Pearson Education, Inc.
Summary
• Climate is classified based on precipitation and
temperature
• There are six primary groups of world climates
• The tropical humid climates exist at tropical latitudes and
are characterized by warm, constant temperatures and
rainfall
• Dry climates exist near the subtropics and are
characterized by hot, dry conditions
• Mild midlatitude climates constitute a transition between
warmer tropical climates and cold severe midlatitude
climates
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41. © 2011 Pearson Education, Inc.
Summary
• Mild midlatitude climates typically have long and hot
summers and mild winters, and have modest
precipitation
• Severe midlatitude climates only occur in the Northern
Hemisphere
• Severe midlatitude climates have long, cold winters and
short summers, and have large annual temperature
ranges
• Polar climates receive little insolation and are
permanently cold and dry
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42. © 2011 Pearson Education, Inc.
Summary
• Highland climates depend on elevation of mountainous
terrain for their climate characteristics
• Many paleoclimatology methods are used to understand
the Earth’s past climate
• There are several factors that influence long-term
climate change
• Global warming is related to the increase in carbon
dioxide release by humans
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