Atmosphere and Climate Change
Section 3
Section 3: Climate Change
Preview
• Classroom Catalyst
• Objectives
• The Greenhouse Effect
• Measuring Carbon Dioxide in the Atmosphere
• Rising Carbon Dioxide Levels
• Greenhouse Gases and the Earth’s Temperature
• Global Climate Change
• Modeling Climate Change
Atmosphere and Climate Change
Section 3: Climate Change
Preview, continued
• The Consequences of a Warmer Earth
• Rising Sea Levels
• Global Weather Patterns
• Human Health Problems
• Agriculture
• Effects on Plants
• Effects on Animals
Section 3
Atmosphere and Climate Change
Section 3: Climate Change
Preview, continued
• Recent Findings
• Reducing the Risk
Section 3
Atmosphere and Climate Change
Classroom Catalyst
Section 3
Atmosphere and Climate Change
Section 3
Objectives
• Explain why Earth’s atmosphere is like the glass in a
greenhouse.
• Explain why carbon dioxide in the atmosphere appears
to be increasing.
• Identify one possible explanation for the increase in
average global temperature.
• Describe what a warmer Earth might be like.
Atmosphere and Climate Change
Section 3
The Greenhouse Effect
• Earth is somewhat comparable to a greenhouse. Earth’s
atmosphere acts like the glass in a greenhouse.
• Sunlight streams through the atmosphere and warms
Earth. As this energy in the form of heat radiates up from
Earth’s surface, some of it escapes into space. The rest
is absorbed by gases in the troposphere and warms the
air.
• This process of warming Earth’s surface and lower
atmosphere is called the greenhouse effect.
Atmosphere and Climate Change
The Greenhouse Effect
Section 3
Atmosphere and Climate Change
Section 3
The Greenhouse Effect
• Not every gas in our atmosphere reradiates infrared
radiation in this way.
• A greenhouse gas is a gas that absorbs and reradiates
infrared radiation from the sun.
• The major greenhouse gases are water vapor, carbon
dioxide, methane, and nitrous oxide. Of these, water
vapor and carbon dioxide account for most of the
absorption of that occurs in the atmosphere.
Atmosphere and Climate Change
Section 3
Measuring Carbon Dioxide in the Atmosphere
• In 1985, a geochemist named Charles Keeling installed
an instrument at the top of a tall tower on the Mauna Loa
observatory in Hawaii.
• Keeling wanted to precisely measure the amount of
carbon dioxide in the air, far from forests and cities
where carbon dioxide levels vary every day.
Atmosphere and Climate Change
Section 3
Measuring Carbon Dioxide in the Atmosphere
• The winds that blow steadily over Mauna Loa have come
thousands of miles across the Pacific Ocean, far from
most forests and human activities, swirling and mixing as
they traveled.
• Keeling reasoned that at Mauna Loa, the average
carbon dioxide levels for the entire Earth could be
measured.
Atmosphere and Climate Change
Section 3
Measuring Carbon Dioxide in the Atmosphere
• Much of the carbon dioxide that is released into the air
dissolves in the ocean or is used by plants for
photosynthesis.
• During the summer, growing plants use more carbon
dioxide for photosynthesis than they release in
respiration, causing the levels to drop.
• In the winter, dying grasses and fallen leaves decay and
release the carbon that was stored in them, causing
levels to rise.
Atmosphere and Climate Change
Section 3
Rising Carbon Dioxide Levels
• After a few years of measurement, it was obvious that
the levels were undergoing changes other than seasonal
fluctuations.
• Each year, the high carbon dioxide levels of winter were
higher, and each year, the summer levels did not fall as
low.
• Since 1958, the level of carbon dioxide in the
atmosphere has increased by over 20 percent. This
increase is due largely to the burning of fossil fuels.
Atmosphere and Climate Change
Rising Carbon Dioxide Levels
Section 3
Atmosphere and Climate Change
Section 3
Greenhouse Gases and Earth’s Temperature
• Most scientists think that because greenhouse gases
absorb and rerelease infrared radiation to Earth’s
surface, more greenhouse gases in the atmosphere will
result in an increase in global temperature.
• A comparison of carbon dioxide in the atmosphere and
average global temperatures for the past 400,00 years
supports this view.
Atmosphere and Climate Change
Section 3
Greenhouse Gases and Earth’s Temperature
• Today, we are releasing more carbon dioxide than any
other greenhouse gas into the atmosphere.
• Millions of tons of carbon dioxide are released into the
atmosphere each year from power plants that burn coal
or oil, and cars that burn gasoline. Millions of trees are
burned in tropical rainforest to clear the land for farming.
• The amount of greenhouse gases including carbon
dioxide, methane, and nitrous oxide in the atmosphere is
increasing.
Atmosphere and Climate Change
Greenhouse Gases
Section 3
Atmosphere and Climate Change
Section 3
Global Climate Change
• Global warming is a gradual increase in the average
global temperature. Because the rise in temperature
correlates to the increase in greenhouse gases in the
atmosphere, most scientists conclude that the increase
in greenhouse gases, and other factors, have caused the
increase in temperature.
• Earth’s average global temperature increased during the
20th century and many scientists predict that this
warming trend will continue. Thousands of experiments
and computer models support this hypothesis.
Atmosphere and Climate Change
Global Climate Change
Section 3
Atmosphere and Climate Change
Section 3
Global Climate Change
• Temperatures are not necessarily rising at a constant
rate, or rising in all parts of the world.
• As with changes in carbon dioxide levels, short-term
variations in temperature are superimposed on larger
trends such as changes in patterns of precipitation,
frequency of fires, and extreme weather events.
• So, most scientists use the term global climate change
rather than global warming.
Atmosphere and Climate Change
Section 3
Modeling Climate Change
• Predictions about climate change are based on
computer models.
• Scientists use mathematical relationships among
“drivers,” such as solar input, wind patterns, and cloud
cover and “response variables,” such as troposphere
temperature, sea surface temperature, ice cover, and
sea level. These relationships are expressed as
equations within complex models.
Atmosphere and Climate Change
Section 3
Modeling Climate Change
• The resulting models can be used to predict how factors
such as temperature will be affected. Scientists validate
the models by starting with historical conditions and then
comparing model projections to know changes in
climate.
• The models are constantly being updated with new
information. About a dozen different models similarly
predict widely increasing temperatures that are not
simply driven by natural climate or solar variability.
• Humans are playing some role in climate change.
Atmosphere and Climate Change
Section 3
The Consequences of a Warmer Earth
• In North America, some birds are nesting two weeks
earlier than they did 50 years ago. In Britain, many
plants are flowering up to 55 days earlier in the year than
they did 40 years ago.
• The possible effects of climate change include a number
of potentially serious environmental problems, such as
changes in weather patterns and rising sea levels.
• The possible effects of a warmer Earth will not be the
same everywhere and countries will vary in their ability to
respond.
Atmosphere and Climate Change
Section 3
Rising Sea Levels
• Sea level has been measured in many locations over the
past 100 years. Sea levels are rising and will continue to
rise.
• Sea levels rise because as water warms, it expands.
Also, ice that is currently over land is melting and the
water is flowing into the ocean.
• The rise is sea levels could flood coastal wetlands and
other low-lying areas. Beaches could be eroded, the
salinity of bays and estuaries, and coastal freshwater
aquifers might increase, negatively affecting aquatic life
and decreasing freshwater resources.
Atmosphere and Climate Change
Section 3
Global Weather Patterns
• If the Earth warms up significantly, the surface of the
oceans will absorb more energy in the form of heat,
which may make hurricanes and typhoons more intense.
• Some scientists are concerned that climate change will
also cause a change in ocean current patterns, such as
slowing of the Gulf Stream.
• Such a change could significantly affect the world’s
weather. Severe flooding could occur in some regions at
the same time droughts and fires devastate other
regions.
Atmosphere and Climate Change
Section 3
Human Health Problems
• Greater numbers of-heat related deaths could occur.
• Since trees and flowering plants would flower earlier and
for longer than they do win, people who are allergic to
pollen would suffer from allergies for more of the year.
• Warmer temperatures could enable mosquitoes, vectors
of diseases such as malaria and Dengue Fever, to
establish themselves in areas that are too cold for them
currently.
Atmosphere and Climate Change
Section 3
Agriculture
• Agriculture would be most severely impacted by climate
change if extreme weather events, such as drought,
became more frequent.
• Higher temperatures could result in decreased crop
yields.
• As a result, the demand for irrigation could increase,
which would further deplete aquifers that have already
been overused.
Atmosphere and Climate Change
Section 3
Effects on Plants
• Climate change could alter the range of plant species
and could change the composition of plant communities.
• A warmer climate could cause trees to colonize
northward into cooler areas.
• Forests could shrink in areas in the warmer part of their
range and lose diversity. Increased frequency of fires
may shift whole ecosystems.
Atmosphere and Climate Change
Section 3
Effects on Animals
• Climate change could cause a shift in the geographical
range of some animals. For example, Northern birds
may not have to migrate as far south during the winter.
• Warming of surface waters of the ocean might cause a
reduction of zooplankton, tiny shrimp-like animals, that
many marine animals depend on for food.
• Warming tropical waters may kill algae that nourish
corals, thus destroying coral reefs. As more carbon
dioxide dissolves into oceans, the water could become
more acidic, which could disrupt food webs.
Atmosphere and Climate Change
Section 3
Recent Findings
• The International Panel on Climate Change (IPCC)
issued its Fourth Assessment Report (FAR) in 2007 that
described what was currently known about about the
global climate system and provided future estimates.
• The IPCC reported that the average global surface
temperature increased by 0.74ºC since their third report
in 2001. The temperature increase is both global and
higher at northern latitudes. Also, the average global sea
level continues to rise, and the concentrations of
atmospheric greenhouse gases have continued to
increase as a result of human activities.
Atmosphere and Climate Change
Section 3
Reducing the Risk
• The need to slow global climate change has been
recognized by the global community. Some nations and
organizations have engaged in reforestation projects to
reduce carbon dioxide.
• However, the attempt to slow global climate change is
made difficult by the economic, political, and social
factors faced by different countries.
Atmosphere and Climate Change
Section 3
Reducing the Risk
• Conflict has already arisen between developed and
developing countries over future CO2 emissions.
• Developing countries are projected to make up half of all
CO2 emissions by 2035.
Atmosphere and Climate Change
Section 3
Reducing the Risk
• The Kyoto Protocol is an international treaty, first
negotiated in 1990, in attempt to reduce greenhouse gas
emissions.
• Many countries have ratified the treaty, but not those
most responsible for the greatest greenhouse gas
emissions, including the United States. Scientists,
governments, organizations, businesses, and individuals
are trying to find ways to reduce greenhouse gas
emissions and address the effects of global climate
change.
Atmosphere and Climate Change
Reducing the Risk
Section 3