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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

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Chapter 8: Climate and Climate Change


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    1. Chapter 8: Climate and Climate Change

    2. 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

    3. 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

    4. Climate Classification • Köppen 3 letter code system • 1st = group • 2nd = precipitation • 3rd = temperature

    5. World Distribution of Major Climate Types • Weather records: How do we explain their locations? Figure 8-11

    6. 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 World Distribution of Major Climate Types Figure 8-4

    7. 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 onmonthly rainfall Figure 8-5

    8. 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

    9. 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: cTor cP air masses

    10. 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

    11. 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

    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 & short-lived • Hot temperatures • Large daily temperature range • Dominant Controls • Subsidence from (STHs) • Cold ocean currents

    13. 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 rainfallconcentration • Dominant Controls • Similar to BWh Figure 8-17

    14. 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

    15. World Distribution of Major Climate Types • Midlatitude steppe climate (BSk) • RringeBWk 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

    16. 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

    17. 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

    18. 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

    19. 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

    20. 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

    21. 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

    22. World Distribution of Major Climate Types Figures 8-31a & 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

    23. 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

    24. 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

    25. 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

    26. 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

    27. 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

    28. 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

    29. 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

    30. 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

    31. 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

    32. 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

    33. 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

    34. 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

    35. 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

    36. 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