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


• 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


• Köppen 3 letter code system– 1st = group – 2nd = precipitation – 3rd = temperature

World Distribution of Major Climate Types

Figure 8-11

• Weather records: How do we explain their locations?

• 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


• 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 onmonthly rainfall

Figure 8-5


• 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

Figures 8-6a & 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

Figures 8-8a & 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

Figures 8-10a & b


• 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


• Subtropical desert climate (BWh)– Near STH’s (30° N/S)– Precipitation is scarce,

unreliable, intense & short-lived

– Hot temperatures– Large daily

temperature range– Dominant Controls

• Subsidence from (STHs)

• Cold ocean currents

Figures 8-14a & b


• Subtropical steppe climate (BSh)– Fringe BWh climates– Separate deserts from humid

climates– Less extremes

• Cooler & more rainfall (semi-arid)

– Seasonal rainfallconcentration

– Dominant Controls• Similar to BWh

Figure 8-17


• 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

Figures 8-18a & b


• Midlatitude steppe climate (BSk)– Rringe BWk climates

• Transition between desert & humid climates

– More precipitation than mid-latitude deserts (semi-arid)

– Less temperature extremes than mid-latitude deserts

– Dominant Controls • Similar to BWk

Figure 8-19


• 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


• 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

Figures 8-21a & b


• 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


• 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

Figures 8-26a & b


• 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


• 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


• 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


• 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


• 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


• 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

Figures 8-34a & b


• 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


• 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 datingFigure 8-42


• 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


• 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


• 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

Figures 8-46a & b


• 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


• 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


• Climate models– General circulation

models (GCMs)– Numerous

assumptions– Model accuracy

• Addressing global warming– Kyoto protocol– Standards for new

industrialized countries

– Mitigating & adapting

Figure 8-47b

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• 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

Chapter 8: Climate and Climate Change

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