Chapter 14 Notes

• Climate is the collective state of the atmosphere for a given place over a specified interval of time.
• Climate sums up the weather’s long term behavior.
• Climate includes a location, time, and averages and extremes of variables.
• The five basic factors that affect climate are: latitude, elevation, topography, proximity to large bodies of water, and prevailing atmospheric circulation.
• Climate is divided into climate zones which identify regions with similar characteristics.
• The Koppen Classification Scheme is the most widely used classification scheme. It has six main groups or zones:
• Tropical Moist (A)- divided into three subtypes: Tropical Wet Climates (Af), Tropical Wet and Dry Climates (Aw), Tropical Monsoon (Am). The mean monthly temperature is high in these climates.
• Dry (B)- divided into two subtypes: Steppe or Semiarid (BS) and arid or desert (BW). There is more land area in B climates than any other single type of climate. Evaporation exceeds precipitation in these climates.
• Moist with Mild Winters (C)-characterized by humid and mild winters. There are three major subgroups: Marine West Coast (Cfb (warm summer) or Cfc (cool summer)), Humid Subtropical (Cfa (wet year round) or Cwa (definite seasonal precipitation cycle)), and the Mediterranean (Csa or Csb (both dry summer and wet winter))
• Moist with Severe Winters (D)- tend to be located in the eastern continents, usually have snow on the ground for extended periods. There are two basic climate subtypes: Humid Continental (extreme temperature change with severely cold winters and cool-to-warm summers) and Subarctic (very long range in annual temperature, winters are long and cold, and summers are brief and cool).
• Polar (E)- occur poleward of the Arctic and Antarctic circles. They are extremely cold and have little precipitation. There are two polar climate subtypes: Tundra (ET, have a layer below the surface that is perennially frozen known as Permafrost) and Ice Caps (EF).
• Highland (H)- regions associated with high elevations regardless of other variables like latitude. A wide variety of climates are exhibited in this zone. They usually have a large diurnal temperature variation.

• Some groups are also classified by two and three letter designations, with the second letter referring to whether and when a dry season occurs, and the third letter denotes differences in temperature.
• Past climates can be divided into two main, unequal categories:
• Historical Climate- the climate of the past several thousand years, during which humans have kept some sort of record of climate conditions.
• Paleoclimate refers to climate conditions that existed in the billions of years before the dawn of human civilization.

• Tree Ring width can be used to gather information about climates from several thousand years ago up to recent times. Dendrochronology is the science of studying tree rings to ascertain a climatic condition.
• Pollen Records can also reveal regional climatic conditions.
• Ice can hold clues to climate, with bubbles of air trapped in ice that can provide a record of the concentration of atmospheric gases such as carbon dioxide and methane over the past several hundred years. Dust can also be analyzed in ice sheets.
• Marine Sediments can help track past climates through the calcium carbonate in animal shells, which can be measured for different versions of oxygen atoms, or isotopes. These varying isotopes can reveal different climatic periods by their shifting concentration.
• Fossils also provide useful insight into the distant past by analyzing the layer of ground in which they lie.
• Volcanic eruptions can affect local, regional, and even local climate through their ash and chemical emissions, which can cool the Earth for a few years.
• Solar Variability, Asteroid Impacts, and Variations in Earth’s Orbit all affect climate.
• Plate tectonics is the theory of continental movement, and the motions of continents undoubtedly affect climate on very long time scales.
• Pangea refers to approximately 300 years ago when all the continents were joined as one supercontinent.
• Ocean Circulation Patterns can influence climate through abrupt climate change such as during the Younger Dryas period which occurred 12,000 to 11, 000 years ago.