CHAPTER 10
CLIMATE – PAST, PRESENT, AND FUTURE
Important Concepts
1. Climate is the long term, average temperature and precipitation for a given geographic region.
2. Global climate change is a worldwide increase (global warming) or decrease (global cooling) in
atmospheric temperature.
3. Earth is warmed by the sun when intense sunlight is absorbed by soil, rock, vegetation, and water, then
is radiated back to the atmosphere as heat.
4. Gases, such as carbon dioxide and water vapor, help trap the heat radiated from earth’s surface, thus
maintaining a relatively warm and life friendly atmospheric temperature. This benefit from heat retentive
gases is called “the greenhouse effect.”
5. Changes in the amount of any greenhouse gas in the atmosphere may profoundly change global earth
temperature. A decrease in greenhouse gas concentration may cause global cooling. An increase in the
concentration of these gases may cause global warming.
6. Presently, earth is in a warming period that is associated with melting polar ice caps, retreating glaciers,
and thawing permafrost.
7. Earth’s oceans buffer differences in temperature. Water gains and loses heat slowly. Consequently,
oceans tend to moderate changes in temperature.
8. Ocean temperature may vary locally and episodically. A notable example is El Nino/La Nina cycles in
the eastern Pacific Ocean. Local changes in sea temperature can alter weather patterns over a short interval
of time.
9. Changes in sea temperature in conjunction with melting ice cause variations in salt concentration in sea
water. In turn, these variations can alter the behavior or existence of ocean currents. These ocean currents,
called thermohaline currents, are important climate regulators by transporting heat from one location to
another. Great Britain, for example, would have a much colder climate if not for the Gulf Stream that
transmits heat from the Gulf of Mexico to the British Isles.
10. Global climate change influences temperature extremes, the amount of precipitation, frequency of
floods, soil moisture, plant growth, animal migration patterns, and the spread of disease. Political strife
may develop because poorer nations may be less able to cope with changes in climate.
11. Past global climate changes are keys to future changes. Interpreting past climate changes, though, is
difficult due to limited evidence.
12. Through understanding climate feedback mechanisms, predictions can be made for climate response to
changes, such as changes in temperature. A positive feedback is a direct relationship between climate
response and change. For example, increasing global temperature causes the amount of ice to be globally
reduced. Ice is highly reflective of sunlight. With less ice cover on land, more sunlight is absorbed and
radiated back as heat than what happened when ice cover was geographically more extensive. This
represents an further increase in temperature, a direct correspondence to initial warming. A negative
feedback represents an inverse relationship between change and response. As atmospheric temperature
increases, likewise does the amount of water evaporated from the oceans. In turn, this higher atmospheric
water content creates more clouds. Clouds, like ice, are highly reflective of sunlight. The more extensive
that cloud cover is, the lesser is the amount of sunlight reaching earth’s surface and the lesser is the amount
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of heat that is radiated back to the atmosphere. This lesser radiance of heat represents a cooling. In this
case, increased atmospheric temperature results in cooling, an inverse response.
Key Terms
Atlantic Multidecadal Oscillation (AMO)
Carbon dioxide
Climate
Climate change
Climate feedback mechanisms
El Nino
Global climate
Greenhouse effect
Greenhouse gases
La Nina
Methane
Pacific Decadal Oscillation (PDO)
Permafrost
Thermohaline circulation
Water vapor
Multiple Choice
1. Which of the following is an example of negative feedback to global warming:
a. polar ice melt decreases surface albedo thus further increasing warming;
b. increased cloud cover due to increased water evaporation brought about by
global warming results in a decrease in global temperature;
c. glacial retreat caused by global warming reduces surface albedo thereby
increasing warming;
d. warming increases sea temperature thus causing more carbon dioxide to
be released into the atmosphere by oceans thereby increasing warming.
2. Of the following gases, the one that is a greenhouse gas:
a. oxygen
b. carbon dioxide
c. nitrogen
d. argon
3. Sea level rise resulting from global warming occurs because sea water expands and
a. winds become stronger
b. ice caps and glaciers melt
c. less water is needed by plants
d. all of these factors
4. Each of the following has a significant influence on global climate except
a. El Nino cycles
b. solar brightness
c. greenhouse gas concentration
d. the Earth-sun distance
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5. In terms of millions of years, this process has a major influence on ocean currents and
consequently global climate
a. biological evolution
b. plate tectonics
c. deforestation and aforestation
d. the Coriolis effect
6. Effects of recent warming have resulted in all of the following except
a. melting of permafrost
b. glacial retreat
c. melting of the polar ice caps
d. decreasing sea level
7. Which of the following may be a beneficial aspect of global warming:
a. increased agricultural growing season
b. changes in insect migration patterns
c. desertification
d. coastal flooding
8. Greenhouse gases:
a. trap heat in the atmosphere that radiates from Earth’s surface
b. maintain Earth’s average temperature at a comfortable 15oC
c. include carbon dioxide and water vapor
d. all of these
9. The energy that is the source of the heat radiated into the atmosphere by Earth’s
surface is
a. radioactivity in Earth’s interior
b. visible light from the sun
c. friction due to the moon’s pull on Earth
d. none of these
10. The most significant greenhouse gas is
a. water vapor
b. carbon dioxide
c. methane
d. chlorofluorocarbons (CFCs).
Fill in the Blanks
1. Earth’s surface is warmed by the sun when _______________ is absorbed and changed to heat.
2. As ice melts, Earth’s surface ____________ decreases causing further warming.
3. Rising sea level due to global warming is the result of two principal factors, melting ice and
______________ .
4. ________________ is a greenhouse gas that is necessary to the process of photosynthesis in plants.
5. ________________ is driven by differences in the density of seawater that varies with temperature and
salinity.
6. During the 20th Century, Earth’s average temperature increased by about _________.
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7. The most likely cause of recent increases in carbon dioxide concentration (an increase of 45 ppm, for
example, in the 30-year period, 1960-1990) is the use by humans of
_______________ fuels.
8. Presently, signs of warming are more significant in the northern hemisphere in comparison to the
southern hemisphere. This paradox can be explained on the basis of changes in _______________
currents.
9. A substantially better understanding of past global climate change has resulted from the study of
___________________ obtained from Greenland and Antarctica.
10. Earth’s average temperature is __________________ .
True or False
1. T
F
Thermohaline ocean currents are controlled by temperature and wind.
2. T
F If sea level rises due to global warming, rivers emptying into the sea
will experience more frequent flooding.
3. T
F There are more hurricanes today than in the past.
4. T
F Methane represents the largest amount of greenhouse gas in the
atmosphere.
5. T
F Water vapor is a greenhouse gas.
6. T
F Without greenhouse gases in the atmosphere, life on Earth would
not be possible.
7. T
F Ocean currents and climate change are linked.
8. T
F On the basis of atmospheric concentration (amount), carbon dioxide
is the most significant greenhouse gas.
9. T
F Global warming will likely increase the spread of diseases.
10. T F Human activity is not thought to have a significant impact on
global climate.
Review Questions
1. What are thermohaline ocean currents? How does thermohaline circulation influence climate?
2. What is anthropogenic global warming?
3. How is Earth’s surface warmed by the sun?
4. Give one example of positive climate feedback and one example of negative climate feedback.
5. What role, if any, do plate tectonics play in climate change?
6. How can climate change result in political strife within and between nations?
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Surfing the Net.
Climate change:
http://www.climate.org/topics/
Quiz on climate change:
http://webprojects.ei.columbia.edu/eiquizzes/quiz.php?qid=4
Global Change Data and Information:
http://globalchange.gov/
CHAPTER 10 ANSWER KEY
Multiple Choice
1.
2.
3.
4.
5.
b
b
b
a
b
6.
7.
8.
9.
10.
d
a
d
b
a
Fill In the Blanks
1.
2.
3.
4.
5.
6. 0.6oC (1.08oF)
7. fossil
8. thermohaline; or ocean
9. ice cores
10. 15oC (59oF)
sunlight; or visible light
albedo
thermal expansion
carbon dioxide
thermohaline circulation
True or False
1. False. Temperature and salinity.
2. True
3. False. The intensity (power; or force) of hurricanes is increasing, but the number of these storms is
not.
4. False. Water vapor, at 2% of Earth’s total atmospheric volume, is the most significant greenhouse gas.
5. True
6. True
7. True
8. False. Water vapor, at 2% of Earth’s total atmospheric volume, is the most significant greenhouse gas.
9. True
10. False. There is considerable scientific and popular attention that is presently focused on this issue,
with a widespread belief that humans play a significant role in global warming.
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