MET 112 Global Climate Change Lecture 11

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MET 112 Global Climate Change - Lecture 11

• Recent Climate Change
• Dr. Eugene Cordero
• San Jose State University

• Outline
• Recent trends in temperature
• Recent trends in GHGs
• Time scales

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(b) Additionally, the year by year (blue curve)
and 50 year average (black curve) variations of
the average surface temperature of the Northern
Hemisphere for the past 1000 years have been
reconstructed from proxy data calibrated
against thermometer data (see list of the main
proxy data in the diagram). The 95 confidence
range in the annual data is represented by the
grey region. These uncertainties increase in more
distant times and are always much larger than in
the instrumental record due to the use of
relatively sparse proxy data. Nevertheless the
rate and duration of warming of the 20th century
has been much greater than in any of the previous
nine centuries. Similarly, it is likely7 that the
1990s have been the warmest decade and 1998 the
warmest year of the millennium.
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Examples of Temperature Change

• Trends
• Periodic Oscillations
• Random Variations
• Jumps

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Examples of Temperature Change

• Draw the following
• Trend
• Oscillation
• Trend Oscillation
• Random variations
• Random trend
• Jump
• Random jump

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Trend
Temperature
100
80
60
40
20
0
Time
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Graph
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Oscillation
Temperature
100
80
60
40
20
0
Time
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Trend Oscillation
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Random Fluctuations
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Random Fluctuations Trend
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Jump
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Jump Random Fluctuations
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Time Frames -- Examples

• Seconds to minutes
• Hours Diurnal Cycle (Caused by Earths
  Rotation)
• Hours to Days
• Months Seasonal Cycle (Caused by tilt of axis)
• Years
• Decades -- Pacific Decadal Oscillation
• Centuries Warming during 20th Century
• (Increase in greenhouse gases?)
• Tens of thousands of Years
• Millions of Years

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Time Frames -- Examples

• Seconds to minutes Small-Scale Turbulence
• Hours Diurnal Cycle (Caused by Earths
  Rotation)
• Hours to Days Weather Systems
• Months Seasonal Cycle (Caused by tilt of axis)
• Years El Niño
• Decades -- Pacific Decadal Oscillation
• Centuries Warming during 20th Century
• (Increase in greenhouse gases?)
• Tens of thousands of Years Irregularities in
  Earths motions
• Millions of Years Geologic Processes

Climate Variability
Climate Change
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• Over both the last 140 years, the best estimate
  is that the global average surface temperature
  has increased
• What does this mean?
• The Uncertainty ( 0.2C ) is critical component
  to the observed trend

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• Over both the last 140 years, the best estimate
  is that the global average surface temperature
  has increased by 0.6 0.2C (IPCC 2001)
• So the temperature trend is 0.6C 0.2C
• What does this mean?
• Temperature trend is between 0.8C and 0.4C
• The Uncertainty ( 0.2C ) is critical component
  to the observed trend

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Current CO2 370 ppm
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What Changed Around 1800?

• Industrial Revolution
• Also, extensive changes in land use began

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What Changed Around 1800?

• Industrial Revolution
• Increased burning of fossil fuels
• Also, extensive changes in land use began
• the clearing and removal of forests

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The (Almost) Complete Long-Term Carbon Cycle
(Diagram)
Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere
(Organic Carbon)
Subduction/Volcanism
Oxidation of Buried Organic Carbon
Silicate-to-Carbonate Conversion
Organic Carbon Burial
Carbonates
Buried Organic Carbon
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Burning of Fossil Fuels

• Fossil Fuels Fuels obtained from the earth are
  part of the buried organic carbon reservoir
• The burning of fossil fuels is essentially
• A large acceleration of the oxidation of buried
  organic carbon

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Burning of Fossil Fuels

• Fossil Fuels Fuels obtained from the earth are
  part of the buried organic carbon reservoir
• Examples Coal, petroleum products, natural gas
• The burning of fossil fuels is essentially
• A large acceleration of the oxidation of buried
  organic carbon

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Land-Use Changes

• Deforestation
• The intentional clearing of forests for farmland
  and habitation
• This process is essentially an acceleration of
  one part of the short-term carbon cycle

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Land-Use Changes

• Deforestation
• The intentional clearing of forests for farmland
  and habitation
• This process is essentially an acceleration of
  one part of the short-term carbon cycle
• the decay of dead vegetation

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Natural Short-Term Carbon Cycle Quantitative
Carbon Content 750 Pg
Atmosphere
Carbon Flux 120 Pg/year
Carbon Flux 90 Pg/year
Carbon Content 38, 000 Pg
Carbon Content 2000 Pg
Biosphere
Ocean
1 Pg 1015 g
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CO2 Measurements 1958 - Present
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CO2 Measurements 1958 - Present
Oscillation reflects breathing of globe NH has
more vegetation
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Carbon Budget Changes

• Units in Peta-grams (x1015) of Carbon per year
  (PgC/yr)
• Atmosphere increase
• Emissions (fossil fuel, cement)
• Ocean-atmosphere flux
• Final component is Land/atmosphere flux

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Carbon Budget Changes

• Units in Peta-grams (x1015) of Carbon per year
  (PgC/yr)
• Atmosphere increase 3.3 0.1
• Observations
• Emissions (fossil fuel, cement) 5.4 0.3
• Estimates from industry
• Ocean-atmosphere flux -1.9 0.6
• Estimates from models/obs
• Final component is Land/atmosphere flux

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Carbon Budget (II)

• Land atmosphere flux
• Land atmosphere flux partitioned as follows 
• Land use change
• Residual terrestrial sink

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Carbon Budget (II)

• Land atmosphere flux
• Must be to balance budget

-0.20.7

• Land atmosphere flux partitioned as follows 
• Land use change
• From observations

1.7
-1.9

• Residual terrestrial sink
• Calculated to balance land/atmosphere flux

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Human Perturbation of the Carbon Cycle
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Missing Carbon Sink Land or Ocean
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Carbon Budget (III)

• There are significant uncertainties related to
  these budget terms.
• Main questions are related to
• Can biosphere/ocean take up more atmospheric CO2?
• What are the carbon fluxes over different types
  of ecosystems
• Tropical forests, Temperate forests, Boreal
  forests, Tropical savannas grasslands,
  Temperate grasslands shrub lands, deserts and
  semi deserts, Tundra, Croplands, Wetlands

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Carbon Budget (III)

• There are significant uncertainties related to
  these budget terms.
• Main questions are related to
• Can biosphere/ocean take up more atmospheric CO2?
• What are the carbon fluxes over different types
  of ecosystems
• Tropical forests, Temperate forests, Boreal
  forests, Tropical savannas grasslands,
  Temperate grasslands shrub lands, deserts and
  semi deserts, Tundra, Croplands, Wetlands
• What happens if the land/ocean get saturated
  with carbon?

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Carbon Budget (III)
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Carbon Budget (III)
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Greenhouse Gases

• Carbon Dioxide
• Methane
• Nitrous Oxide
• CFCs (Chlorofluorocarbons)
• Others

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Methane
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Anthropogenic Methane Sources

• Leakage from natural gas pipelines and coal mines
• Emissions from cattle
• Emissions from rice paddies

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Anthropogenic Methane Sources

• Leakage from natural gas pipelines and coal mines
• Emissions from cattle
• Flatulencegas
• Emissions from rice paddies

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Nitrous Oxide
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Anthropogenic Sources of Nitrous Oxide

• Agriculture

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CFCs
CFC-11
CFC-12
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Sources of CFCs

• Leakage from old air conditioners and
  refrigerators
• Production of CFCs was banned in 1987 because of
  stratospheric ozone destruction
• CFC concentrations appear to now be decreasing
• Lecture on ozone depletion to follow later in
  semester

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Sources of CFCs

• Leakage from old air conditioners and
  refrigerators
• Production of CFCs was banned in 1987 because of
  stratospheric ozone destruction
• CFC concentrations appear to now be decreasing
• There are no natural sources of CFCs
• Lecture on ozone depletion to follow later in
  semester

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Activity 6

• How would you describe the temperature record in
  terms of the seven above described types of
  temperature variations for the
• Past 1000 years
• Past 150 years
• Based on the past 150 years of globally averaged
  temperatures
• What trend(s) could you assign to this period.
  Give your answer in C over a certain number of
  years (i.e. 0.3C over 20 years)