Mesothermal Climates (C)

1. Mesothermal Climates (C)   • Humid Subtropical (Hot-Summer) Climates (Cfa)   • Humid Subtropical (Winter-Dry) Climates (Cwa) • Marine West Coast Climates (Cfb, Cfc)   • Mediterranean Dry-Summer Climates (Csa, Csb)  

2. Mesothermal Climates (C)   • Humid Subtropical (Winter-Dry) Climates (Cwa) C = warmest month above 10ºC, coldest month above -3ºC = seasonal climates • a = hot summer, warmest month above 22ºC • w = winter dry (> 70% of rainfall concentrated in summer months)

3. Mesothermal Climates (C)  

4. Microthermal Climates • Humid Continental Hot-Summer Climates • Dfa, Dwa • Humid Continental Mild-Summer Climates • Dfb, Dwb • Subarctic Climates • Subarctic Cool-Summer: Dfc, Dwc • Subarctic Extreme-Winter: Dfd, Dwd

5. Microthermal Climates (D) • Subarctic Climates (Dfc, Dwc, Dwd) • Found poleward of Dfb and Dwb climate. • Extensive geographically: • North America, stretching from Atlantic to Pacific. • Eurasia, stretching from Scandinavia to the Pacific. • Subarctic extreme-winter found only in eastern Asia • Most extreme temperature ranges of all climates • Extremely cold temperatures in winter primarily due to: • continental locations = Siberian High in winter • higher latitudes • cP air masses

6. Microthermal Climates (D)

7. Polar and Highland Climates • Tundra Climate (ET) • Ice Cap and Ice Sheet Climates (EF) • Polar Marine Climate (aka “Polar Maritime”) EM • More moderate than other two polar climates (why?) • No month below -7°C (20°F), but not as warm as tundra climate • Low annual range of temperature • Exists only along very fringes of highest latitudes • Bering Sea (Alaska, Russia), southern Greenland, northern Iceland, Norway)

8. Polar and Highland Climates

9. Chapter 10Climate Change Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen

10. Causes of Climate Change • Variations in the Earth’s orbital characteristics • Atmospheric carbon dioxide variations • Volcanic eruptions • Variations in solar output • Humans

11. Greenhouse Gases • Human activities are enhancing the Earth’s natural greenhouse effect • Carbon dioxide, methane, nitrous oxide, CFCs, and water vapor • Greenhouse gases are transparent to sunlight but opaque to longwave radiation

13. Carbon Dioxide • Atmospheric CO2 levels began rising during the Industrial Revolution • Tremendous fossil fuel burning and heavy deforestation increased CO2 levels – this trend continues • CO2 is responsible for 64% of global warming

14. Carbon Dioxide Sources

15. What are the Fossil Fuels?

16. Carbon Dioxide Sources

17. Methane • Methane currently increasing faster than CO2 in the atmosphere • 19% of total atmospheric warming attributed to methane • Methane generated by rotting vegetation, digestion in cattle and termites, burning of vegetation, and melting permafrost

18. Methane (CH4)

19. Volcanic Eruptions • Sulfur dioxide reacts with water vapor causing haze • Combined with ejected particulate matter • One of the coldest years in the last two centuries was 1816, the “Year Without a Summer” • Caused by eruption of Tambora in 1815 • Temperatures can decrease after eruptions for up to 3 years Mount St. Helens

20. Variations in Solar Output • Climate models predict that a change in solar output of only 1 percent per century alters the Earth’s average temperature by 0.5 -1.0° C • Sunspots • Huge magnetic storms • Seen as dark (cooler) areas on the sun's surface. • Cycle every 11, 90, and 180 years

21. GCM Predictions • Crop patterns and natural plant/animal habitats will shift to maintain preferred temperatures • During this century, climate regions could shift 90-350 miles poleward • Soil moisture projected to decrease in midlatitudes

22. GCM Predictions • Forest cover will undergo major species disturbances • Expansion of zones affected by tropical diseases • Alpine glaciers

23. High point: 1998 = +0.7 Low point: 1884 = -0.7 Global Temperatures 1.4°C = 2.5°F Figure 10.28

24. Temperature Anomalies for 2003 Figure 10.28

25. Sea Level Issues During this century, global warming will cause sea levels to rise at least 1.5 meters (about 4.5 feet).

26. Sea Level Rise • During the 20th century, sea level rose 4-8 inches • Could rise 3.5-34.7 inches this century • Thermal expansion of water will increase sea level rise • Higher sea levels = destruction of small island nations, river deltas, lowland coastal farming, barrier islands

27. July 2029 Temperature Forecast Figure 10.31

28. Disintegration of Ice Shelves • In 2002, Larsen-B ice shelve collapsed in 35 days after existing for 11,000 years • Warmer ocean and air temperatures are melting shelves on both sides • Clear evidence of changes in Earth’s energy balance

29. Antarctic Ice Disintegration Figure 10.32

30. Arctic Climates • Changes in ocean temperatures could alter global temperatures • Arctic region warmed 9°F since 1987 • This has led to a freshening of northern oceans • Greenland ice melting at 1m/year • Permafrost is melting • Increased precipitation in Arctic/Antarctic areas

31. End of Chapter 10Climate Change Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charlie Thomsen