Download Chapter 13: Global Climate Change

13
GLOBAL CLIMATE CHANGE
A Warming Planet?
PowerPoint® Lecture prepared by Gary A. Beluzo
STUDENT LEARNING OUTCOMES
After reading this chapter, students will be able to
•
Identify the factors that affect the amount
of energy that enters and leaves the
Earth’s atmosphere and how this affects
global temperature.
•
Explain the effect of human activity on
climate based changes in storages and
flows in global biogeochemical cycles.
•
Explain how detection and attribution are
critical to climate change policy.
•
Describe the positive and negative
effects of climate change on
environmental and economic systems.
•
Describe the factors that determine
economically efficient climate change
policy and what it implies about the
Kyoto Protocol.
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Climate Change and Norse Settlements
• Norse farmers set up colonies in Iceland, Greenland,
Newfoundland, and North America.
• Settlement began in Medieval Warm Period
• On Greenland the Norse settlements persisted for 450
years (984 to sometime in early 1400s)
• Greenland Norse disappeared suddenly
• Arrival of the Inuit and the Little Ice Age
• Less farming and more reliant on local wildlife but Inuit
better hunters
• Lack of food confirmed by bones
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Climate versus Weather
Weather
Climate
• Atmospheric conditions at
particular place and time
• Average weather conditions
over a long period
• How it changes from day to
day
• Repeating pattern of
weather
• Temperature, precipitation,
wind speed, cloud cover,
humidity, etc
• Average temperature and
average precipitation
Climate Change is a shift in the long-run
average of weather
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Climate Change- Rule not Exception
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The Heat Balance of Planet Earth
Climate Change is caused by a change in the planet’s
heat balance (energy in versus energy out).
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The Greenhouse Effect
• The ability of the atmosphere to absorb energy with
longer wavelengths and convert it to heat
• Natural phenomena that warms the lower atmosphere
by about 35 degrees Celsius
• Greenhouse gases
• Water vapor (H2O)
• Carbon dioxide (CO2)
• Methane (CH4)
• Nitrous Oxide (N2O)
• Chlorofluorocarbons (CFCs) not natural
• Particles and Aerosols
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Radiative Forcing
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Residence Time
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Hemispheric Radiative Forcing
• Greenhouse gases well
mixed throughout entire
atmosphere
Figure 13.4a
• Sulfate aerosols have
variable residence time;
and incomplete mixing
Figure 13.4c
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Figure 13.4b
Greenhouse Gases
Figure 13.5a
Figure 13.5b
Figure 13.5c
Figure 13.5d
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Carbon Dioxide, Methane, and
Temperature
Figure 13.6
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Disrupting the Global Carbon Cycle
• Nearly all greenhouse gases and sulfur aerosols at or
near maximum value observed over last 500,000 years
• Largely due to human activities that have disrupted the
global biogeochemical cycles of C,N, and S.
• Carbon (as CO2 and CH4)
• Fossil fuel combustion (coal releases the most)
• Coal mining
• Land-Use Change (deforestation and agriculture)
• Landfills
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Carbon Dioxide Futures
Figure 13.7
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Disrupting the Global Sulfur Cycle
• Coal combustion
• Reflect sunlight and enhance cloud formation
• Will sulfur emissions Increase or Decrease?
• Pollution abatement technologies are promising
• But emissions could increase if world coal increases
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Detecting Climate Change
• Choose an indicator
• Direct measurement of mean annual global temperature
• Sea level change
• Size of glaciers
• Remote Sensing of Vegetation (growing season and biomass)
• Organism behavior (migrations, leaf out, onset of breeding)
• Measure the mean and natural variability
• Are recent changes greater than expected based on
natural variability?
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Detecting Climate Change
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Detecting Climate Change
Figure 13.10
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Attribution
• Establishing cause and effect relationship between
human activity and the observed change in climate.
• The IPCC suggests there is a discernible human
influence on climate
• Statistical Analyses of Historical Data
Figure 13.11
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Climate Models
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The Role of Human Activity
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The IPCC
An Interdisciplinary Effort To Make Climate Change
Policy states “The warming over the past 100 years is very
unlikely to be due to internal variability alone…and is
unlikely to be entirely natural in origin…Detection and
attribution studies consistently find evidence for
anthropogenic signal in the climate record of the last 25-50
years…most of the observed warming over the last 50 years
is likely to have been due to the increase in greenhouse gas
concentrations.”
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Skeptics?
• Reluctance to slow down emissions?
• Incomplete understanding of the science?
• The State of Fear by Michael Crichton
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Satellite/Thermometer Discrepancy
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How Will Humans Affect Climate?
• The 460,000 year climate
record shows a
correlation between
greenhouse gases and
temperature
• But did one cause the
other?
• “chicken-or-egg problem”
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Why Does Temperature Rise?
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The Impacts of Global Climate Change
• The 3.5 degree C rise in mean annual global
temperature from doubling in the radiative forcing
similar to glacial to interglacial
• Most of North America covered by ice
• Boreal forests covered what is now North Carolina
• As climate warmed 10,000 years ago, tree species
shifted their range north about 100-400 meters/year
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Figure 13.18a
Figure 13.18b
Figure 13.18c
Figure 13.18d
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Impacts to Vegetation
• Slow rate of movement important because climate
change forecast by models is about 10x faster
• Impediments to migration
• Cities, highways, agricultural fields
• Soils may be different
• Forest Biomes could get trapped and collapse
• Replaced with simpler systems, lower biodiversity, etc
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Impact to Food Supplies (Positive?)
• Food production would increase in some areas and
decrease in others
• Doubling of CO2 may increase yield of spring wheat by
8-10 %
• Higher concentrations may allow farmers to increase
production in arid areas (water use efficiency)
• Where growing season is currently too short global
warming could allow farming in the future
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Impact to Food Supplies (Negative?)
• Most of world’s best agricultural areas are located in
the middle of continents- these are forecast to dry
• More suitable habitats for pests and diseases in the
future
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Rising Seas
• IPCC forecasts sea level will rise about 0.39 meters
• 0.29m is due to thermal expansion
• 0.11m is due to melting of mountain glaciers and icecaps
• Complete melting of the Antarctic and Greenland ice
sheets would raise sea levels by 70 meters
• 20% of world’s population lives within 30 km of ocean
and 40% live within 100 km
• 0.5 meter rise could destroy $20-150 billion human
infrastructure in the U.S.
• Also reduce area and productivity of estuaries and
coastal wetlands
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Species Extinction
• Toads first species to go
extinct due to climate
change
• High altitudes in Central
American cloud forests
• 9-52% of world’s known
terrestrial species could go
extinct
• Climate envelope
• Worst case: 38-52%
• Best case: 9-13%
• World corals?
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Climate Change Policy
• Human Activity is changing climate
• Our activities now will result in future changes
• Policy can only slow not prevent climate changes
• Not economical to eliminate all activities that emit
greenhouse gases
• Optimal level of pollution
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Damage Functions
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The Kyoto Protocol: A First Step?
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