Download Introduction - San Jose State University

MET 112 Global Climate Change – Lecture 7
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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MET 112 Global Climate Change
(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.
Examples of Temperature Change
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
Trends
Periodic Oscillations
Random Variations
Jumps
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Examples of Temperature Change

Draw the following:
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Trend
Oscillation
Trend + Oscillation
Random variations
Random + trend
Jump
Random + jump
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Trend
Temperature
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MET 112 GlobalTime
Climate Change
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Graph
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Temperature
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This graphs represents
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Trend
Oscillation
Trend+Oscillation
Random variation
Random+Trend
Jump
Random+Jump
Temperature
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Oscillation
Trend+Oscillation
Random variation
Random+Trend
Jump
Random+Jump
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Temperature
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Trend
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Trend+Oscillation
Random variation
Random+Trend
Jump
Random+Jump
O
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Temperature
This graphs represents
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Oscillation
Trend+Oscillation
Random variation
Random+Trend
Jump
Random+Jump
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Temperature
This graphs represents
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Trend+Oscillation
Random variation
Random+Trend
Jump
Random+Jump
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Temperature
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Trend+Oscillation
Random variation
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Temperature
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Time Frames -- Examples
 Seconds to minutes – Small-Scale Turbulence
 Hours – Diurnal Cycle (Caused by Earth’s
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
Earth’s motions
 Millions of Years – Geologic Processes
Latest global temperatures
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MET 112 Global Climate Change
…“Over the last 140 years, the best estimate is that the
global average surface temperature has increased by
0.6 ± 0.2°C” (IPCC 2001)
 So the temperature trend is:
0.6°C ± 0.2°C
 What does this mean?
 Temperature trend is between 0.8°C and 0.4°C
 The Uncertainty (± 0.2°C ) is critical component to the
observed trend
Current CO2: ~383 ppm
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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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:
– the decay of dead vegetation
 Also causes change in surface albedo
(generally cooling)
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Natural Short-Term Carbon Cycle –
Quantitative
Carbon Content: 750 Pg*
Carbon Flux:
~ 120 Pg/year
Atmosphere
Carbon Content:
38, 000 Pg
Carbon Content:
2000 Pg
Biosphere
Carbon Flux:
~ 90 Pg/year
1 Pg =
1015
g
Ocean
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Carbon
Budget
Example
Atmosphere
1.5
Note: Number are not
real…only for practice
Land
Land emission =1.3
Ocean emission = 3.0
Ocean
Positive values refer to
carbon going into the
atmosphere
Land uptake = -2.3
Ocean uptake = ?
What is the ocean uptake required to produce an atmosphere at 1.5?
The ocean update is:
+1.5
-1.5
-0.5
0
1.0
-1.0
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0
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Carbon
Budget
Example
Atmosphere
1.5
Note: Number are not
real…only for practice
-1.0
Land
Land emission =1.3
Ocean emission = 3.0
-0.5
3.0
Ocean
Land uptake = -2.3
Ocean uptake = ? -0.5
What is the ocean uptake required to produce an atmosphere at 1.5?
Carbon
Budget
Example Notes…
Land/atmosphere Flux = Land emission + Land uptake
Ocean/atmosphere Flux = Ocean emission + ocean uptake
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:
 What is the land/atmosphere flux?
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Carbon
Budgets
Atmosphere
3.3 PgC
5.4 PgC
Land
Land/atmosphere flux
Fossil
fuel
burning
-1.9 PgC
Ocean
Ocean/atmosphere flux
Please make your selection...
+4.0
-4.0
+3.5
-3.5
+0.2
-0.2
95%
5%
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Carbon
Budgets
Atmosphere
3.3 PgC
-0.2 PgC
Land
Land/atmosphere flux
5.4 PgC
Fossil
fuel
burning
-1.9 PgC
Ocean
Ocean/atmosphere flux
Carbon Budget (II)
 Land atmosphere flux
– Must be to balance budget
-0.2±0.7
Land atmosphere flux partitioned as follows
 Land use change
– From observations
1.7
 Residual terrestrial sink
 Calculated to balance land/atmosphere flux
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Carbon
Budgets
Atmosphere
3.3 PgC
-0.2 PgC
Land use
change
1.7 PgC
Land
5.4 PgC
Fossil
fuel
burning
-1.9 PgC
Ocean
Land/atmosphere flux
So, now considering the land use change, what is the new Land/atmosphere flux?
What is the residual land sink?
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2.
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-1.9
-1.7
+0.2
1.5
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Carbon
Budgets
Atmosphere
3.3 PgC
-1.9
-0.2 PgC
Land use
change
1.7 PgC
Land
5.4 PgC
Fossil
fuel
burning
-1.9 PgC
Ocean
Land/atmosphere flux
So, now considering the land use change, what is the new Land/atmosphere flux?
Carbon Budget (II)
 Land atmosphere flux
– Must be to balance budget
-0.2±0.7
Land atmosphere flux partitioned as follows
 Land use change
– From observations
1.7
 Residual terrestrial sink
-1.9
 Calculated to balance land/atmosphere flux
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Human Perturbation of the Carbon Cycle
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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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Video – Global Warming – signs and the
science
 Explain the concept of ‘ancient sunlight’ and
how it relates to the carbon cycle.
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Carbon Budget (III)
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Greenhouse Gases
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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
– Flatulence…gas
 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
– There are no natural sources of CFCs
Lecture on ozone depletion to follow later in
semester…
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Latest global temperatures
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Activity
1. Describe the 120 year temperature records in terms of
the seven above described types of variations (trend,
trend+oscillation etc.) by breaking up the time series
into periods (i.e. from 1930-1950, oscillation + positive
trend, from 1950-1970, negative trend)
2. Based on the past 120 years of globally averaged
temperatures:
a. What trend would you assign to this period. (i.e.
0.3°C over 120 years)
b. If you were to break up the data into time sections
provide trends over the following time periods i)
1880-1920; b) 1920-1940 and c) 1970-2000
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How would you describe the last 30
years of temperature
Random
Oscillation
Oscillation+trend
Oscillation+jump
Random+jump
Trend
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What is the approximate temp trend
over the last 30 years?
0.6C/30 years
1.0C/30 years
.1C/30 years
0.2C/30 years
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0%
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2C
/3
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C/
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What is the approximate temperature trend
over the last 100 years?
+0.2C/10 years
+0.5C/10 years
+0.1C/10 years
0.0C/10 years
MET 112 Global Climate Change
ar
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/1
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Temperature over the last 10 years
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Comparison of 1998 with 2005
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The Land and Oceans have both warmed
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Precipitation patterns have changed
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Activity 11 Question
 Explain how humans may affect precipitation in
a city.
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