Chapter 8: Climate and Climate Change

Report
Chapter 8: Climate and
Climate Change
Climate Classification
• Purpose of Classifying Climates
– Understand climate distribution
– Compare climates of different places
• Temperature & precipitation
typically used
– Vegetation
• Earliest scheme = ancient
Greeks 2200 years ago
• Classified 3 climate regions
based on latitude
– Torrid, Temperate, Frigid
Figure 8-1
Climate Classification
• Köppen climate classification system
– Based on annual & monthly average temperature & precipitation
• A, B, C, D, E, H*
– 4 of 5 major groups classified by temperature
– 5th group classified by precipitation
– Subdivided further based on temperature & precipitation relationships
Figure 8-2
Climate
Classification
• Köppen 3 letter code system
– 1st = group
– 2nd = precipitation
– 3rd = temperature
World Distribution of Major
Climate Types
• Weather records: How do we explain their locations?
Figure 8-11
World Distribution of Major
Climate Types
• Three Questions
– Where are various climate
types located?
– What are the characteristics
of each climate?
– What are the main controls of
each climate?
• Climograph
– Graphic representation of
monthly temperature &
precipitation
Figure 8-4
World Distribution of Major
Climate Types
• Tropical Humid Climates (A)
– Tropics (0-25° N/S)
– Winterless climates; little temperature change
– High temperatures & prevalent moisture
• Precipitation influenced by ITCZ
– 3 subtypes
• Divided
based on
monthly
rainfall
Figure 8-5
World Distribution of Major
Climate Types Figures 8-6a & b
• Tropical wet climate (Af)
– Equatorial (0-10º N/S)
– Monotonous
• Daily temperature range >
annual range
• High humidity
• High precipitation
– Multiple rains daily
– Afternoon
convective storms
– Evenly distributed
rain during year
– Influenced by ITCZ
• High solar angle
year round
World Distribution of Major
Climate Types Figures 8-8a & b
• Tropical savannah climate
(Aw)
– N/S of Af climates
– Most extensive A climate
– Seasonal wet/dry alteration
due to ITCZ position
• Lowest tropical
rainfall amounts
– Dominant Controls
• Summer: ITCZ
• Winter: cT or cP air
masses
World Distribution of Major
Climate Types Figures 8-10a & b
• Tropical monsoonal climate (Am)
– Prominent monsoon wind patterns
• Coastal areas
– Extensive rainfall during “summer”
• Cherrapunji, India = 425 in
– Cloud cover reduces summer
temperatures
– Dominant Controls
• ITCZ movement
• Jet stream fluctuation
• Continental pressure
changes
World Distribution of Major
Climate Types
• Dry climates (B)
– Cover about 30% of land area worldwide
– Dry conditions all year
•
PE > P
– Lack of uplift or lack of moisture
– 2 main types
(precipitation)
•
•
Desert
Steppe
– 2 subtypes
(temperature)
•
•
Subtropical
Midlatitude
Figure 8-12
World Distribution of Major
Climate Types Figures 8-14a & b
• Subtropical desert climate
(BWh)
– Near STH’s (30° N/S)
– Precipitation is scarce,
unreliable, intense & shortlived
– Hot temperatures
– Large daily
temperature range
– Dominant Controls
• Subsidence from
(STHs)
• Cold ocean
currents
World Distribution of Major
Climate Types
• Subtropical steppe climate
(BSh)
– Fringe BWh climates
– Separate deserts from humid
climates
– Less extremes
• Cooler & more
rainfall (semi-arid)
– Seasonal rainfall
concentration
– Dominant Controls
• Similar to BWh
Figure 8-17
World Distribution of Major
Climate Types Figures 8-18a & b
• Midlatitude desert climate
(BWk)
– Meager & erratic precipitation
• Mostly in summer
– Cooler temperatures
• Hot summers &
cold winters
– Greater annual &
daily temperature
range
– Dominant Controls
• Rain shadow
effects
• Distance from
moisture sources
World Distribution of Major
Climate Types
• Midlatitude steppe climate (BSk)
– Rringe BWk climates
• Transition between desert &
humid climates
– More precipitation than midlatitude deserts
(semi-arid)
– Less temperature
extremes than midlatitude deserts
– Dominant Controls
• Similar to BWk
Figure 8-19
World Distribution of Major
Climate Types
• Mild Midlatitude Climates (C)
– Transition between warmer tropical climates & colder severe midlatitude
climates
• Equator-ward side of mid-latitudes
– Long, hot summers & short, mild winters
– Highly
variable
precipitation
– 3 primary
groups
Figure 8-20
World Distribution of Major
Climate Types Figures 8-21a & b
• Mediterranean Climate
(Csa, Csb)
– West sides of continents
– Modest precipitation in winter,
summer is virtually rainless
– Mild, wet winters &
hot, dry summers
• Clear skies especially
in summer
– Dominant Controls
• Summer: STH
• Winter: westerlies &
cyclones
World Distribution of Major
Climate Types
• Humid Subtropical Climate (Cfa, Cwa)
– East sides of continents
– Warm to hot summers; high humidity
• Hot & humid
– Precipitation reaches summer maximum,
less in winter
– Winter
temperatures are
mild to cold
Figures 8-24a & b
World Distribution of Major
Climate Types Figures 8-26a & b
• Marine West Coast Climate
(Cfb, Cfc)
– West sides of continents
– Often cloudy with precipitation
• Wettest of midlatitudes
• Max precipitation in winter
– Temperate climate
• Very mild winters
for latitude
– Dominant Controls
• Westerly winds &
oceanic influence
year-round
World Distribution of Major
Climate Types
• Severe Midlatitude Climates (D)
– Only in Northern Hemisphere
– Continentality—remoteness from oceans
• Large annual temperature range
• Precipitation varies; diminishes inland & poleward
– 4 recognizable
seasons
• Long, cold
winter &
shorter
summer
– Subdivided into
2 types
Figure 8-27
World Distribution of Major
Climate Types
• Humid Continental Climate (Dfa, Dfb, Dwa, Dwb)
– East sides of continents in N.
Hemisphere
– Dominated by westerlies & frequent
weather changes
– Warm/hot summers, cold winters
• Large annual temperature range
– Generally low precipitation
• Higher near coasts
– Winter precipitation =
cyclones; summer
precipitation = convection
– Our climate in NE
Figures 8-28a & b
World Distribution of Major
Climate Types
• Subarctic Climate (Dfc, Dfd, Dwc, Dwd)
– Winters are long, dark, bitterly cold
– Summers are short
• Spring & fall are very short
– Coldest temperatures; little precipitation
• Largest annual temperature ranges
– (-90 °F to 98 °F in
Verhoyansk, Siberia)
– Dominant Controls
• Continentality
• Alternate between:
– Westerlies/storms
– Anticylcones
Figures 8-31a & b
World Distribution of Major
Climate Types
• Polar Climates (Group E)
– Receive little insolation
– Coldest summers
• No average temperature above 50 °F
• Large annual temperature range
• Small daily
temperature
range
– Extremely dry,
but classified
as non-arid
• Low
evaporation
– 2 primary groups
Figure 8-27
World Distribution of Major
Climate Types
• Tundra Climate (ET)
– Long, dark winters
• Winters not as severely
cold as subarctic climate
– Brief, cool summers
– Little precipitation
– Dominant Controls
• Latitude
• Distance from heat/moisture
sources
• Extreme contrasts in
sunlight/darkness
• Polar anticyclones
– (A & cP air masses)
Figures 8-33a & b
World Distribution of Major
Climate Types Figures 8-34a & b
• Ice Cap Climate (EF)
–
–
–
–
Greenland & Antarctica
Permanent ice & snow cover
High latitude with high altitude
Very limited precipitation
• Polar deserts
– Dominant Controls
• Similar to ET
World Distribution of Major
Climate Types
• Highland Climate (H)
– Infinite variations from place to place
• Vertical climate zonation
– Altitude vs. Latitude
» Altitude = more significant in highlands
– -6.5°C /1000m
– Exposure: windward or leeward
Figure 8-36
Global Patterns
Idealized
• Understand climate locations &
relationships
– Presumed arrangement of climate types
on hypothetical
continent
• Example: Africa
– Only continent
with equal land
N/S of equator
Figures 8-39 & 40
Global Climate Change
• Changes in climate on long time scales
• Episodic events vs. long-term global climate change
• Numerous time scales
– 70 million years:
global cooling trend
– 150,000 years:
temperature fluctuated
– 10,000 years:
sharp warmup
– 150 years:
warming trend relative
to last 1000 years
Figure 8-41
Global Climate Change
• Paleoclimatology
– Proxy measures of climate
• Dendrochronology
– Study of past climate via tree ring
analysis
• Oxygen isotope analysis/Ice cores
– Lighter vs. heavier isotopes (18O : 16O)
– Ratio of 18O/ 16O = thermometer
– Atmospheric composition
measurements
• Coral reefs
– Ratio of 18O/ 16O & reef height
• Pollen data
– Radiocarbon dating
Figure 8-42
Global Climate
Change
• Causes of Long-Term Climate Change
– Atmospheric aerosols
• Block insolation & lower temperature
• Due to volcanic eruptions or asteroid
impacts
• Anthropogenic impacts
– Solar output fluctuations
• Sunspot activity vs. solar output
– Roles of the oceans
• Absorb large amounts of carbon
• Methane hydrates
• Heat transfer from low latitudes to
high latitudes
Figures 8-43 & 45
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
• Negative feedback mechanisms
– Variations in Earth-Sun relations
• Milankovitch cycles
– Shape of Earth’s orbit (eccentricty)
– Inclination of Earth’s axis (obliquity)
– Position of Earth’s axis (precession)
Figure 8-44
Global Climate Change
Figures 8-46a & b
• Evidence of global warming
– 11 of 12 warmest years on record
occurred between 1995–2006
– Global temperature increasing
• Arctic temps ↑ 2 x’s global rate
– Ocean temperatures increasing
– Sea level rise
• Thermal expansion
• Melting ice caps & glaciers
–
–
–
–
Arctic sea ice decreasing
# of intense tropical cyclones ↑
Water vapor in atmosphere ↑
Changes in precipitation
amounts
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
Figure 8-F
Global Climate Change
• Consequences of global warming
– Projected climate in the upcoming century
• Climate will warm about
0.4°F per decade
• Changes will be greater
than those during 20th c.
• Estimated temperature
increase from 3.3°F - 7.2°F
• Sea level rise
• Stronger tropical cyclones
• Increased precipitation
Figure 8-47a
Global Climate Change
Figure 8-47b
• Climate models
– General circulation
models (GCMs)
– Numerous
assumptions
– Model accuracy
• Addressing global
warming
– Kyoto protocol
– Standards for new
industrialized
countries
– Mitigating &
adapting
Summary
•
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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
Mild midlatitude climates typically have long, hot summers & 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
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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