Earth Science

Chapter 18: Climate

    I. The climate system

       A. Climate is an aggregate of weather

       B. Involves the exchanges of energy and moisture that occur among the

             1. Atmosphere

             2. Hydrosphere

             3. Solid Earth

             4. Biosphere, and

             5. Cryosphere (ice and snow)

  II. World climates

       A. Every location has a distinctive climate

       B. The most important elements in a climatic description are

             1. Temperature, and

             2. Precipitation

III. Climate classification

       A. Brings order to large quantities of information

       B. Many climatic-classification systems have been devised

       C. Köppen classification of climates

             1. Best known and most used system

             2. Uses mean monthly and annual values of temperature and precipitation

             3. Divides the world into climatic regions in a realistic way

             4. Boundaries Köppen chose were largely based on the limits of certain plant associations

IV. Köppen climates

       A. Humid tropical (A) climates

             1. Winterless climates, with all months having a mean temperature above 18°C

             2. Two main types

                  a. Wet tropic

                 b. Tropical wet and dry-Tropical grassland (savanna)

       B. Dry (B) climates

             1. Evaporation exceeds precipitation and there is a constant water deficiency

             2. Two climatic types

                  a. Arid or desert (BW)

                 b. Semiarid or steppe (BS)

                      1. More humid than arid climate

                      2. Surrounds desert

             4. Causes of deserts and steppes

                 b. Middle-latitude deserts and steppes

                      1. Most are located in the Northern Hemisphere

       C. Humid middle-latitude climates with mild winters (C climates)

             1. Average temperature of the coldest month is below 18°C but above -3°C

                  a. Marine west coast

                 b. Dry-summer subtropics-Mediterranean climate

       D. Humid middle-latitude climates with severe winters (D climates)- Absent in the Southern 

       E. Polar (E) climates

             1. Mean temperature of the warmest month is below 10°C

             2. Enduring cold

             3. Meager precipitation

             4. Two types of polar climates

                  a. Tundra climate (ET)

                 b. Ice cap climate (EF)

        F. Highland climates- Usually cooler and wetter than adjacent lowlands

  V. Human impact on global climate

       A. Humans have been modifying the environment over extensive areas for thousands of years

             1. By using fire

             2. By overgrazing of marginal lands

       B. Most hypotheses of climatic change are to some degree controversial

       C. Global warming

             1. Water vapor and carbon dioxide absorb heat and are largely responsible for the

                 greenhouse effect of the atmosphere

             2. Burning fossil fuels has added great quantities of carbon dioxide to the atmosphere

       D. The atmosphere response

             1. Global temperatures have increased

                  a. Balance of evidence suggests a human influence on global climate

                 b. Globally averaged surface temperature is projected to increase by 1.4 to 5.8°C by the

                      year 2100

             2. The role of trace gases

                  a. Atmospheric race gasses

                      1. Methane

                      2. Nitrous oxide

                      3. Certain chlorofluorocarbons

                 b. Absorb wavelengths of outgoing Earth radiation

                  c. Taken together, their warming effects may be nearly as great as carbon dioxide

VI. Climate feed-back mechanisms

       A. Possible outcomes of altering the climate-system

       B. Two types

             1. Positive -feedback mechanisms reinforce the initial change

             2. Negative-feedback mechanisms produce results that are just the opposite of the initial

                 change and tend to offset it

 VII. Some possible consequences of global warming

       A. Altered distribution of the world’s water resources and the affect on the productivity

             of agricultural regions

       B. Rise in global mean sea level

       C. Changing weather patterns

             1. Higher frequency and intensity of hurricanes

             2. Shifts in the paths of large-scale cyclonic storms

             3. Changes in frequency and intensity of heat waves and droughts

Notes taken from Tarbuck and Lutgens Website