Download Lesson 7 - Climate Change - Hitchcock

Unit 4 Lesson 7 Climate Change
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Unit 4 Lesson 7 Climate Change
The Temps are a-Changin’
What are some natural causes of
climate change?
• The weather conditions in an area over a long
period of time are called climate.
• Natural factors have changed Earth’s climate
many times during our planet’s history.
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Unit 4 Lesson 7 Climate Change
What are some natural causes of
climate change?
• Tectonic plate motion has contributed to long-term
climate change over billions of years.
• The present continents once fit together as a
single landmass called Pangaea.
• As Pangaea broke up, some continents moved
closer to the equator and grew warmer. Other
continents moved to higher latitudes and became
colder.
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Unit 4 Lesson 7 Climate Change
What are some natural causes of
climate change?
• How was the climate on various continents
affected by the breakup of Pangaea?
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Unit 4 Lesson 7 Climate Change
What are some natural causes of
climate change?
• Short-term changes in climate can be due to
natural events that send tiny, solid particles called
particulates into the atmosphere.
• Particulates absorb some of the sun’s energy and
reflect some of it back into space. This process
temporarily lowers temperatures on Earth.
• Particulates can come from asteroid impacts and
volcanic eruptions.
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Unit 4 Lesson 7 Climate Change
What are some causes of repeating
patterns of climate change?
• The output of energy from the sun is slightly
higher during times of higher sunspot activity.
• Sunspot activity tends to increase and decrease in
a cycle that lasts approximately 11 years.
• The effect of this cycle on global temperatures is
not dramatic, but there appears to be a link
between sunspot activity and global rain patterns.
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Unit 4 Lesson 7 Climate Change
What are some causes of repeating
patterns of climate change?
• Climate is also affected by changes in ocean
temperature, such as happen during El Niño and
La Niña conditions, which usually alternate.
• During El Niño years, ocean temperatures are
above normal in the tropical Pacific Ocean. The
opposite effect occurs during La Niña years.
• Both conditions affect temperatures and rainfall in
different areas, leading to droughts and flooding.
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Unit 4 Lesson 7 Climate Change
What are some causes of repeating
patterns of climate change?
• The geological record shows that at different
times, Earth’s climate has been both cooler and
warmer than it is today.
• Earth’s history contains extremely cold periods
called ice ages. An ice age is a long period of
cooling during which ice sheets spread beyond the
polar regions.
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Unit 4 Lesson 7 Climate Change
What are some causes of repeating
patterns of climate change?
• Geologic evidence indicates that ice ages occur
every 200 million years or so, and each ice age
lasts for millions of years.
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Unit 4 Lesson 7 Climate Change
What are some causes of repeating
patterns of climate change?
• Ice sheets have alternately advanced (glacial
periods) and retreated (interglacial periods).
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Unit 4 Lesson 7 Climate Change
Is It Getting Hotter?
How may humans affect climate
change?
• Certain gases, called greenhouse gases, warm the
Earth’s surface and lower atmosphere by a
process called the greenhouse effect.
• In this process, greenhouse gases absorb and
radiate energy as heat back to Earth. Without
these gases, Earth would be colder.
• Greenhouse gases include carbon dioxide (CO2),
water vapor, methane, and nitrous oxide.
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Unit 4 Lesson 7 Climate Change
How may humans affect climate
change?
• There is evidence to support the idea that by
burning fossil fuels such as gasoline and coal,
humans are causing a rise in global CO2 levels.
• Since the 1950s, scientists have observed a rise in
both CO2 levels and the average global surface
temperature.
• To explain this correlation, scientists note that CO2
is a greenhouse gas, and increasing levels of CO2
will warm Earth’s surface and lower atmosphere.
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Unit 4 Lesson 7 Climate Change
How may humans affect climate
change?
• Processes such as the burning of fossil fuels emit
carbon into the atmosphere and are called carbon
sources.
• Processes such as the growth of plants remove
carbon from the atmosphere and are called
carbon sinks.
• Scientists note that deforestation converts a
carbon sink into a carbon source, thereby playing
a large role in greenhouse gas emissions.
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Unit 4 Lesson 7 Climate Change
How may humans affect climate
change?
• What is the relationship between atmospheric CO2
concentration and average global temperature?
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Unit 4 Lesson 7 Climate Change
What are some predicted effects of
climate change?
• Studies show that the average global surface
temperature has risen by about 0.3 °C to 0.8 °C
over the last 100 years.
• Global warming is a gradual increase in average
global temperature. It will affect global sea level,
global weather patterns, and life on Earth.
• Scientists predict that storms will increase in
power and frequency, and as much as half of
Earth’s surface may be affected by drought.
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Unit 4 Lesson 7 Climate Change
What are some predicted effects of
climate change?
• Rising temperatures will lead to an increase in the
melting of glaciers, arctic sea ice, and ice sheets
that cover Greenland and Antarctica.
• A 2010 report observed record-setting high
temperatures, resulting in record melting of the
Greenland ice sheet.
• Global sea level rose by 10 to 20 cm during the
1900s. Scientists project that sea level may rise
by 60 cm by 2100.
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Unit 4 Lesson 7 Climate Change
What are some predicted effects of
climate change?
• Scientists predict that global warming will change
ecosystems, threatening the survival of many
species. Some species may benefit, however.
• If Earth warms more than a few degrees Celsius,
many of the world’s farms could suffer, though
less severe warming would help agriculture.
• Warmer temperatures could increase the number
of deaths related to heat and certain diseases, but
deaths associated with extreme cold could drop.
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Unit 4 Lesson 7 Climate Change
How are climate predictions made?
• Climate data are being collected by instruments
placed in the atmosphere, in the oceans, on land,
and in space.
• These data, along with historical climate data, are
used to create climate models, which describe
how different variables affect Earth’s climate.
• Scientists use climate models to predict the
effects of an increase in greenhouse gases on
future global climate.
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Unit 4 Lesson 7 Climate Change
Think Clean and Green
How can people reduce their impact on
climate change?
• The Kyoto Protocol, adopted in 1997, is the only
existing international treaty in which nations have
agreed to reduce CO2 emissions.
• Individuals can reduce greenhouse gas emissions
by conserving energy, increasing energy
efficiency, and reducing their use of fossil fuels.
• One can take steps such as driving less, using
nonpolluting energy sources, turning off lights,
and recycling products.
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Unit 4 Lesson 7 Climate Change
How can people reduce their impact on
climate change?
• Deforestation contributes up to 20 percent of
carbon emissions globally.
• Planting trees and supporting reforestation
programs are ways to balance carbon sources with
carbon sinks.
• Another solution is to educate people about the
importance of the carbon that is stored in forests
for stabilizing climate.
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Unit 4 Lesson 7 Climate Change
How can people reduce their impact on
climate change?
• Clean-energy technologies are being researched
and used in different parts of the world.
• New biofuels, solar power, wind power, and water
power reduce the need to burn fossil fuels.
• However, many new technologies are currently
more expensive than fossil fuels.
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Unit 4 Lesson 7 Climate Change
What factors make climate change a
global issue?
• Greenhouse gases enter Earth’s atmosphere
wherever they are produced.
• Consequently, the economic, political, and social
factors related to climate change make it a global
issue.
• However, the need to reduce greenhouse gas
emissions is more often seen as a problem that
affects people locally.
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Unit 4 Lesson 7 Climate Change
What factors make climate change a
global issue?
• The cost of climate change includes the costs of
crop failure, storm damage, and human disease.
• However, developing countries may not be able to
afford technologies needed to reduce human
impact on climate.
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Unit 4 Lesson 7 Climate Change
What factors make climate change a
global issue?
• Political action can lead to regulations that reduce
greenhouse gas emissions.
• However, these laws may be challenged by groups
who disagree with the need for change or object
to the proposed solutions.
• No matter what choices are made to handle the
challenges of climate change, it will take groups of
people working together to make a difference.
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