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Transcript
Climate Control and
Ozone Depletion
Chapter 19
19-1 How Might the Earth’s Temperature and
Climate Change in the Future?
 Concept 19-1 The overwhelming scientific
consensus is that the earth’s atmosphere is
warming rapidly, mostly because of human
activities, and that this will lead to significant
climate change during this century.
Global Warming and Global Cooling
Are Not New
 Over the past 4.7 billion years the climate has
been altered by:
•
•
•
•
Volcanic emissions
Changes in solar input
Movement of the continents
Impacts by meteors
Estimated Changes in the Average Global
Temperature of the Atmosphere
 Over the past 900,000
years, the troposphere
has experienced
prolonged periods of
global cooling and
global warming.
 Since the end of the last
ice age a little more than
10,000 yrs ago, the
temperature has been
relatively stable.
Estimated Changes in the Average Global
Temperature of the Atmosphere
 For the past 1,000 years
temperatures have
remained fairly stable but
began to rise during the
last century.
 This increase coincides
with the beginning of the
industrial revolution, large
scale deforestation, and
the widespread use of
fossil fuels.
Estimated Changes in the Average Global
Temperature of the Atmosphere
 A record of CO2 measurements taken at the top of
Mauna Loa volcano in Hawaii since 1958.
• Commonly known as the “Keeling Curve” after Charles
David Keeling who supervised the measurements
Estimated Changes in the Average Global
Temperature of the Atmosphere
Estimated Changes in the Average Global
Temperature of the Atmosphere
How Do We Estimate
Past Temperature Changes?
 Scientists can estimate the changes in Earth’s
past by analyzing:
• Direct temperature measurements since 1861
• Tree rings
• Pollen from the bottom of deep lakes/bogs
• Bat dung deposited in caves over 1000’s of yrs.
• Ocean floor sediments
• Radioiostopes in rocks and fossils
• Past glaciation formations
• Air bubbles in ancient glaciers…
Science: Ice Cores Are Extracted by Drilling
Deep Holes in Ancient Glaciers
 Scientists analyze the gas
isotopes found in tiny air bubbles
trapped in ice cores to learn
about past:
•
•
•
•
•
•
troposphere composition
temperature trends
greenhouse gas concentrations
solar activity
snowfall amounts
forest fire activity
Our Climate, Lives, and Economies Depend
on the Natural Greenhouse Effect
 Three major factors shape the earth’s climate:
1) The sun
2) The Oceans: store CO2 and heat, evaporate and
receive water, move stored heat to other parts of
the world
3) The Greenhouse effect that warms the earth’s
lower troposphere and surface because of the
presence of greenhouse gases
Our Climate, Lives, and Economies Depend
on the Natural Greenhouse Effect
 The Earth’s average temp is 57º F (14º C)
• Without the natural greenhouse effect the average temp.
would be -2º F (-19º C)
Our Climate, Lives, and Economies Depend
on the Natural Greenhouse Effect
 The major atmospheric greenhouse gases are:
• Water Vapor (H2O): the most abundant greenhouse gas,
warmer air holds more water vapor (positive feedback)
• Carbon Dioxide (CO2): enters the atmosphere through
the burning of fossil fuels, solid waste, trees and wood
products, etc. It is removed from the atmosphere or
“sequestered” when it is absorbed by plants as part of the
carbon cycle.
• Methane (CH4): emitted during the production and
transport of fossil fuels, from livestock and other
agricultural practices, and by the decay of organic waste
in municipal solid waste landfills.
• Nitrous Oxide (N2O): emitted during agricultural and
industrial activities and during combustion of fossil fuels
and solid waste.
Atmospheric Levels of CO2 and CH4, Global
Temperatures, and Sea Levels
Human Activities Emit Large Quantities of
Greenhouses Gases
 Since the Industrial Revolution (1860-2004)
• Average concentrations of CO2, CH4, and N2O
emissions are much higher
• Mostly due to: burning of fossil fuels, agriculture, and
deforestation
Human Activities Emit Large Quantities of
Greenhouses Gases
 Countries with the largest CO2 emissions
1) United States (25%)
2) China (5%)
3) European Union (27 countries)
The Atmosphere Is Warming Mostly Because
of Human Activities
 In 1988, the UN established the Intergovernmental
Panel on Climate Change (IPCC).
 It includes more than 2,500 climate scientists in more
than 130 countries.
 It’s 2007 report indicated a 90–99% likelihood that the
lower atmosphere is warming AND that human activity is
responsible for most of the recent warming.
 Evidence that supports the major conclusions of the IPCC:
•
•
•
•
The 20th century was the hottest in the past 1000 yrs.
1906–2005: Ave. tropospheric temp increased about 0.74˚C
1970–2005: Annual greenhouse emissions up 70%
Past 50 years: Arctic temp rising almost twice as fast as the
rest of the earth
The Atmosphere Is Warming Mostly Because
of Human Activities
 Evidence that supports the major conclusions of the IPCC:
• Glaciers and floating ice sheets are melting and shrinking at
increasing rates
• Prolonged droughts: increasing
• During the last century, sea level rose by 10-20 cm, mostly
due to runoff from melting and land-based ice and the
expansion of ocean water as temperatures rise.
• Warmer temps. in Alaska, Russia, and the Arctic are melting
permafrost releasing more CH4 into the troposphere.
• The range and distribution of plants and animals is shifting
towards the poles.
• In the mid-latitudes, spring is coming earlier and fall is
coming later.
The Atmosphere Is Warming Mostly Because
of Human Activities
May 30, 1868
May 30, 2005
Feedback Loops: Positive and Negative
 Some factors can amplify (positive feedback) and
some can dampen (negative feedback) projected
global warming:
Is a Hotter Sun the Culprit?
 Is a hotter sun the culprit? No.
• Since 1975, the troposphere has warmed while the
stratosphere has cooled.
• A hotter sun would cause the entire atmos. to warm
Can the Oceans Save Us?
 The oceans can absorb large amounts of CO2
• 25-30% of man-made CO2 is absorbed by the ocean
• Some is converted into carbonate salts that sink to bottom
• Some is used by marine plants
 Problems:
• The warmer water is, the less CO2 it can hold
• As the oceans warm, more CO2 will have to stay in the
atmosphere and warm the planet even more
• Positive feedback loop
• CO2 levels increase ocean acidity
• Also decreases CO2 solubility in ocean water
• Effect on coral reefs – dissolves the calcium carbonate
There Is Uncertainty about the Effects of
Cloud Cover on Global Warming
 Warmer temperatures create more clouds that could
shade and cool the troposphere, but water vapor is
also a greenhouse gas.
 Warmer temperatures create more clouds
• Thick, light-colored low altitude clouds: decrease
surface temperature
• Thin, cirrus clouds at high altitudes: increase surface
temperature
 Effect of jet contrails on climate temperature?
Outdoor Air Pollution Can Temporarily
Slow Global Warming
 Aerosol and particulate pollutants produced by
human activities can cool the atmosphere through a
process called global dimming. The high amounts
of pollutants can actually help to shade the planet.
• Ironically, global warming will accelerate as particulate
and SO2 pollution is reduced.
• Creates a cooling effect that may have partially
masked the effects of global warming
• This is why we have seen a slightly lower
global temp. increase than some
climate models predicted.
What Is the Scientific Consensus about
Future Temperature Change?
 Mathematical models used for predictions
• They represent simplified models of major processes that
interact to determine the average temperature and
greenhouse gas content of the troposphere.
 Most models show:
• Global warming will continue to occur at a rapid rate
• Human factors are the major cause of temperature
rise since 1950
• Human activities will play an ever increasing role in
the warming trend during the next century
Simplified Model of Some Major Processes
That Interact to Determine Climate
Troposphere
Greenhouse
gases
Aerosols
Warming
from
decrease
Cooling
from
increase
CO2 removal
by plants and
soil organisms
CO2 emissions
from land
cleaning, fires,
and decay
Heat and
CO2 removal
Heat and
CO2 emissions
Ice and snow cover
Shallow ocean
Land and soil biotoa
Long-term
storage
Natural and human emissions
Deep ocean
Core Case Study:
Studying a Volcano to Understand Climate Change
 NASA scientists correctly predicted that the 1991
eruption of Mount Pinatubo in the Philippines
would cool the average temperature of the earth
by 0.5o C over a 15 month period and then return
to normal by 1995.
 Particulates and SO2 were
the main reasons for the
temp. decrease.
 The success convinced
scientists and policy
makers that climate model
projections should be
taken seriously.
Comparison of Measured Temperature from
1860–2007 and Projected Changes
19-2 What Are Some Possible Effects of a
Warmer Atmosphere?
 Concept 19-2 The projected rapid change in the
atmosphere's temperature during this century is
very likely to increase drought and flooding, shift
areas where food can be grown, raise sea levels,
result in intense heat waves, and cause the
premature extinction of many species.
19-2 What Are Some Possible Effects of a
Warmer Atmosphere?
 Important distinction:
• Global Warming vs. Climate Change
 Global warming = the temperature of the troposphere
increasing as a result of an increase in the natural
greenhouse effect
 Climate change = a broader term referring to any
changes in the Earth’s climate as a result of a warmer
troposphere
19-2 What Are Some Possible Effects of a
Warmer Atmosphere?
 Remember: we are not talking about local weather,
we are talking about global climate.
 A rapid increase in the temperature of the
troposphere during this century would give us little
time to deal with its harmful effects.
 Many scientists fear a “tipping point” after which
rapid/severe climate changes cannot be prevented.
 Plant/animal distribution and ocean/atmosphere
circulations are based on the current global climate.
 What if the climate changes??
Severe Drought Is Increasing:
The Browning of the Earth
 Drought accelerates global warming, leads to more
droughts
•
•
•
•
Severe lack of water
Growth of trees and other plants will slow
Less CO2 taken out of atmosphere
Also, more forest and grass fires will add CO2 to the
atmosphere
 Groundwater, lakes, and rivers will be depleted
because of lack of precip., increased evaporation,
and increased need to agricultural irrigation.
Ice and Snow Are Melting
 Why will global warming be worse in the polar regions?
• Because the ice was reflecting 90% of the sunlight
back into space…when it melts it is replaced by water
which absorbs 90% of the sunlight.
• Positive feedback loop
Ice and Snow Are Melting
Ice and Snow Are Melting
 The world’s sea ice sheets and land-based glaciers
are slowly melting.
• The loss of ice is happening much faster than
scientists thought possible.
 Why should we care if snow and ice are melting?
• Arctic ice regulates the temperature and precipitation
of regions to the south (North America, Europe)
• Mountain glaciers play a vital role in the water cycle
and the availability of fresh water for hundreds of
millions of people.
• Drinking
• Agriculture
Ice and Snow Are Melting
1948
2004
Sea Levels Are Rising
 Average sea level has been slowly rising and the
rate is increasing
• 2/3 of the rise is the from
the thermal expansion of
warm water
• The remaining 1/3 of the
rise is from the melting
of land-based ice
• Floating ice is already
in the water (buoyancy)
Sea Levels Are Rising
 Projected irreversible effect
• Degradation and loss of 1/3 of coastal estuaries,
wetlands, and coral reefs
• Disruption of coastal fisheries
• Flooding of
• Low-lying barrier islands and coastal areas
• Agricultural lowlands and deltas
• Contamination of freshwater aquifers (groundwater)
• Submergence of low-lying islands in the Pacific and
Indian Oceans and the Caribbean
Sea Levels Are Rising
 13% of the world’s
urban population lives
near sea level
 Many cities would be
devastated by even
relatively small
increases in sea level
Areas of Florida to flood
if average sea level
rises by one meter
Permafrost Is Likely to Melt:
Another Dangerous Scenario
 As arctic temperature increases, permafrost melts
and the organic matter in soils and lake bottoms
decomposes, releasing CH4
 Effect on global warming
• Warmer air can release methane gas stored in bogs,
wetlands, and tundra soils and accelerate global warming.
Ocean Currents Are Changing but
the Threat Is Unknown
 Ocean currents act like large conveyor belts redistributing
heat all over the planet.
 Global warming can change ocean currents by increasing
the temp. of the water, adding large amounts of
freshwater from melting ice, and increasing salinity by
increasing evaporation.
 The temp. of water
greatly effects the temp.
of the air above it.
 Many areas have warmer climates despite their higher
latitudes; that will change if the ocean currents change
Extreme Weather Will Increase in Some Areas
 By altering ocean currents and air circulation, global
warming can both excessive warming or cooling.
 This will lead to prolonged heat waves and droughts
in some areas and prolonged heavy rains and
increased flooding in other areas.
 Hurricanes and typhoons feed off the warm ocean
waters. If these waters are warmer, that means
more energy for the storms and stronger storms.
Global Warming Is a Major Threat to Biodiversity
 Habitat loss and ecosystem
changes will cause many
species to seek new
habitats or face extinction.
 Specialist species that
cannot evolve or migrate
fast enough are the most
vulnerable.
• An estimated 30% of land
plants/animals could go
extinct with only a 2ºC
temp. increase
Global Warming Is a Major Threat to Biodiversity
 Most susceptible ecosystems:
• Coral reefs, polar seas, coastal wetlands, alpine and
arctic tundra
Exploding Populations of
Mountain Pine Beetles in
British Columbia, Canada
Changes in Average Ocean Temperatures, Relative to Coral Bleaching Threshold
Climate Change Will Shift Areas
Where Crops Can Be Grown
 Regions of farming may shift
• Decrease in tropical and subtropical areas
• Increase in northern latitudes
• However, it will be less productive; soil not as fertile
 Loss of productivity could be offset by a longer
growing season
 Genetically
engineered crops
developed to be more
tolerant to drought and
temperature extremes
Climate Change Will Threaten
the Health of Many People
 Global warming will increase human deaths from:
•
•
•
•
•
•
•
•
•
Heat stroke
Increased flooding
Malnutrition and starvation from disruption of food supply
Spread of tropical diseases to temperate regions
More insects, microbes, toxic molds, and fungi
Increase in some forms of air pollution, more O3
Decreased amount of vital natural capital
Increased number of environmental refugees
Increased poverty
19-3 What Can We Do to Slow Climate Change?
 Concept 19-3A To slow the rate of global
warming and climate change, we can increase
energy efficiency, sharply reduce greenhouse
gas emissions, rely more on renewable energy
resources, and slow population growth.
 Concept 19-3B Governments can subsidize
energy efficiency and renewable energy use, tax
greenhouse gas emissions, set up cap-and-trade
emission reduction systems, and help to slow
population growth.
Dealing with Climate Change Is Difficult
 Climate change is such a difficult problem to deal
with because:
•
•
•
•
The problem is global
The effects will last a long time
It is a long-term political issue
The harmful and beneficial impacts of climate
change are not spread evenly
• Many actions that might reduce the threat are
controversial because they can impact economies
and lifestyles
What Are Our Options?
 Mitigation – the act of decreasing or reducing something
• Taking actions aimed at reducing the extent of global
warming by reducing the production of greenhouse gases
or their emission into the atmosphere
• We can improve energy efficiency, rely more on carbonfree renewable energy resources, and find ways to keep
much of the CO2 we produce out of the troposphere.
 Adaptation – change along with the changing climate
• We recognize that some warming is unavoidable and
devise strategies to reduce its harmful effects, or live with
the outcome.
Solutions: Global Warming, Methods for
Slowing Atmospheric Warming
Case Study:
Is Capturing and Storing CO2 the Answer?
 Carbon sequestration - removing CO2 from the
atmosphere and storing it
Ways to Prepare for the Possible Long-Term
Harmful Effects of Climate Change
Governments Can Help Reduce the
Threat of Climate Change
 A program to slow and adapt to global warming
now is very likely to cost less than waiting and
having to deal with its harmful effects later.
 Governments can tax greenhouse gas emissions
and energy use, increase subsidies and tax breaks
for saving energy, and decrease subsidies and tax
breaks for fossil fuels.
 Getting countries to agree on reducing their
greenhouse emissions is difficult.
The Kyoto Protocol:
International Climate Negotiations
 In 1997, delegates from 161 countries met in Kyoto,
Japan to negotiate a treaty on global warming which
went into effect January, 2005.
 It requires 38 participating developed countries to
cut their emissions of CO2, CH4, and N2O to 5.2%
below their 1990 levels by 2012.
• This represents a reduction of 2010 levels by 29%
 The protocol implements a “cap-and-trade” program
that involves setting a cap or limit on emissions.
• If a country emits less than their allowed limit, they can
sell the remaining allowances to another country.
• Many countries distribute their allowance to specific
companies or power plants.
 Developing countries were excluded.
The Kyoto Protocol:
International Climate Negotiations
 191 countries have signed and ratified the protocol.
 U.S. signed the protocol but has not ratified it.
• Developing countries such as China, India and Brazil
were considered exempt
• Belief that it would hurt the U.S. economy
 The U.S. did not sign, but 10 U.S. states and 740 U.S.
Cities are participating.
 The Kyoto Protocol will have little effect on global
warming without support and action by the U.S.,
China, and India.
Some Are Reducing Their Carbon Footprints
 What is your carbon footprint?
• The impact you have of the Earth (in terms of CO2
emissions) through your actions, decisions, and
purchases.
 Carbon neutral – a balance between the amount of
carbon released into the atmosphere and the amount
sequestered or removed from the atmosphere
 U.S. cities, states, businesses,
and schools are taking initiatives
to reduce carbon emissions