Unit 1: Climate Variability and Change

In this unit, you have considered climate factors that affected ancient cultures. This study guide provides an opportunity to test your understanding of some of the concepts you have learned, as well as new vocabulary. Test yourself by quizzing yourself on the terms with the definitions hidden below and by answering the concept questions.

New Vocabulary or Terminology:

• climate (how is it different from weather?)
  Show me the definition
  Hide
  The climate of a region is typically characterized by the long-term average of weather conditions. Global climate is characterized by the global average temperature.
• climate variability
  Show me the definition
  Hide
  Climate variability refers to the year-to-year changes in the climate of a region. Often, year-to-year changes from wetter to drier and warmer to cooler are caused by climate variability.
• climate system
  Show me the definition
  Hide
  Refers to the components of the Earth system that respond to and play a role in climate change. These components include the atmosphere, the hydrosphere (oceans, rivers, lakes, etc.), the biosphere, the lithosphere (land surface or terrestrial realm), and the cryosphere (ice).
• forced climate change
  Show me the definition
  Hide
  Any change in climate (may be temporary or permanent) that is forced to occur because to a change brought on by something outside of the climate system. For example, a change in Earth's orbit would create a forced change in climate.
• unforced climate change
  Show me the definition
  Hide
  Changes in the climate system that result from interactions among climate system components. These changes are not forced by anything external to the climate system.
• feedback
  Show me the definition
  Hide
  Amplification or mitigation of an initial change in a system as a result of interactions among the components of the Earth system. It is the feedbacks that lead to unforced climate changes.

Conceptual Questions

1. What factors affect the climate of a particular region?
   Show me the answer
   Hide
   The climate of a particular location is affected by both global and local factors. The global atmospheric composition (for example, the concentration of greenhouse gases in the atmosphere), latitude (northward or southward distance from the equator helps determine how much sunshine a place receives in a given year), altitude (i.e., elevation), proximity to oceans or mountains, direction of ocean currents (if near the ocean), direction of prevailing winds, and surface vegetation type.
2. What external forcing mechanisms can cause a change in global climate?
   Show me the answer
   Hide
   External forcing mechanisms are the things outside of the climate system that can force a change in the entire system. These include changes in the sun's output, changes in Earth's orbit, volcanic eruptions, meteorite impacts, changes in atmospheric composition through human activity.
3. When is a climate feedback positive or negative? (Be able to draw a diagram of both.)
   Show me the answer
   Hide
   A positive feedback occurs when the effect of an initial change in a system is amplified. For example, if Earth's temperature increases because of a higher CO₂ concentration in the atmosphere, the polar ice caps will melt. If this happens, then Earth's albedo (reflectivity) will be lower, and Earth will absorb more energy from the sun. If Earth absorbs more energy from the sun, it will get warmer (so the initial warming is amplified). A negative feedback mitigates the effect of an initial change. For example, again, imagine Earth is warming because of higher concentration of CO₂. With a warmer climate, plants, in some areas, respond positively and are able to grow for a longer period each year, over a larger area. This means that plants will draw down more CO₂ from the atmosphere. Reduced CO₂ in the atmosphere leads to cooling. It is important to note that this negative feedback might not be enough to actually lead to cooling; it may, instead, only be enough to somewhat reduce the warming. In other words, a negative feedback will not necessarily completely negate an initial change; it will simply reduce the impact.

Climate Forecasting and Adaptation through the ages

The questions below test how well you can recall details about the article you read. The article contains other questions that focus more on applying your understanding and considering new perspectives. While those questions do not have specific "right" answers, it would be worth reviewing them, along with your class notes or discussion about those questions, after you have considered the questions below.

Recall Questions

1. Describe how the people of the Andes determined when to plant their crops.
   Show me the answer
   Hide
   In mid- to late June, Andean farmers note the overall appearance of the Pleiades constellation in the pre-dawn sky. An obscured view would lead them to anticipate a dry year, and they would plant their crops later. A clear view would lead them to expect adequate rainfall, and they would plant sooner.
2. Where did the Mayans live?
   Show me the answer
   Hide
   The Mayans lived on the Yucatan Peninsula, in present-day Mexico, and south into Guatemala, Belize, and Honduras.
3. What are climate proxies?
   Show me the answer
   Hide
   Climate proxies are features preserved in the geologic record from which we can infer past climate.
4. How can lake sediments provide information about past climate?
   Show me the answer
   Hide
   The chemistry of the sediments can tell us about evolution of life in the lake, which is related to climate. Specifically, the ratio of heavy to light oxygen can tell us whether a period in time was relatively wet or dry.
5. What is the prevailing hypothesis regarding collapse of the Mayan civilization?
   Show me the answer
   Hide
   The prevailing hypothesis is that a series of droughts led to the collapse of the Mayan civilization.
6. Over the past 5000 years, at least four different groups of people have inhabited Greenland. Where did they all come from?
   Show me the answer
   Hide
   Three of the groups were Inuit peoples, from North America. The fourth group was Norse explorers, known as the Vikings.
7. How did Dr. D'Andrea reconstruct a record of air temperature in Greenland?
   Show me the answer
   Hide
   Dr. D'Andrea used alkenones (fat deposits) from algae in lakes to determine air temperature.
8. Why did the Vikings abandon Greenland?
   Show me the answer
   Hide
   The departure of the Vikings from Greenland has been attributed to regional cooling.