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MET 112 Global Climate Change – Lecture 10
Recent Climate Change
Dr. Craig ClementsSan Jose State University
Outline Recent trends in temperature Recent trends in GHGs Time scales
(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
Draw the following:
1. Trend2. Oscillation3. Trend + Oscillation4. Random variations5. Random + trend6. Jump7. Random + jump
This graphs represents
1. Trend
2. Oscillation
3. Trend+Oscillation
4. Random variation
5. Random+Trend
6. Jump
7. Random+Jump
100806040200Time
Tem
pera
ture
This graphs represents
1. Trend
2. Oscillation
3. Trend+Oscillation
4. Random variation
5. Random+Trend
6. Jump
7. Random+Jump
100806040200Time
Tem
per
atu
re
This graphs represents
1. Trend
2. Oscillation
3. Trend+Oscillation
4. Random variation
5. Random+Trend
6. Jump
7. Random+Jump
100806040200Time
Tem
per
atu
re
This graphs represents
1. Trend
2. Oscillation
3. Trend+Oscillation
4. Random variation
5. Random+Trend
6. Jump
7. Random+Jump
100806040200Time
Tem
per
atu
re
This graphs represents
1. Trend
2. Oscillation
3. Trend+Oscillation
4. Random variation
5. Random+Trend
6. Jump
7. Random+Jump
100806040200Time
Tem
pe
ratu
re
This graphs represents
1. Trend
2. Oscillation
3. Trend+Oscillation
4. Random variation
5. Random+Trend
6. Jump
7. Random+Jump
100806040200Time
Tem
per
atu
re
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
Cli
mat
e C
hang
e
Cli
mat
e “V
aria
bili
ty”
…“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
What Changed Around 1800?
Industrial Revolution– Increased burning of fossil fuels
Also, extensive changes in land use began– the clearing and removal of forests
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
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)
Natural Short-Term Carbon Cycle – Quantitative
Atmosphere
Biosphere Ocean
Carbon Content: 750 Pg*
1 Pg = 1015 g
Carbon Content: 2000 Pg
Carbon Content: 38, 000 Pg
Carbon Flux: ~ 120 Pg/year
Carbon Flux: ~ 90 Pg/year
CarbonBudgetExample
Atmosphere1.5
OceanLand
Land emission =1.3Ocean emission = 3.0
Land uptake = -2.3Ocean uptake = ?
Note: Number are not real…only for practice
Positive values refer to carbon going into the
atmosphere
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 -1
0%
8%
0%3%
0%
89%1. +1.5
2. -1.5
3. -0.5
4. 0
5. 1.0
6. -1.0
CarbonBudgetExample
Atmosphere1.5
OceanLand
Land emission =1.3Ocean emission = 3.0
Land uptake = -2.3Ocean uptake = ? -0.5
Note: Number are not real…only for practice
What is the ocean uptake required to produce an atmosphere at 1.5?
-1.0 3.0-0.5
CarbonBudgetExample 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?
CarbonBudgets
Atmosphere
OceanLandFossil fuel
burning
5.4 PgC -1.9 PgC
3.3 PgC
Land/atmosphere flux Ocean/atmosphere flux
Please make your selection...
4 -4 3.5
-3.5 0.
2-0
.2
0% 0%
95%
5%0%0%
1. +4.0
2. -4.0
3. +3.5
4. -3.5
5. +0.2
6. -0.2
CarbonBudgets
Atmosphere
OceanLandFossil fuel
burning
5.4 PgC -1.9 PgC-0.2 PgC
3.3 PgC
Land/atmosphere flux Ocean/atmosphere flux
Carbon Budget (II)
Land atmosphere flux partitioned as follows
Land use change– From observations
-0.2±0.7
1.7
Land atmosphere flux– Must be to balance budget
Residual terrestrial sink Calculated to balance land/atmosphere flux
CarbonBudgets
Atmosphere3.3 PgC
OceanLandFossil fuel
burning
5.4 PgC -1.9 PgC-0.2 PgC
Land use change1.7 PgC
So, now considering the land use change, what is the new Land/atmosphere flux?
Land/atmosphere flux
CarbonBudgets
Atmosphere3.3 PgC
OceanLandFossil fuel
burning
5.4 PgC -1.9 PgC-0.2 PgC
Land use change1.7 PgC
-1.9
So, now considering the land use change, what is the new Land/atmosphere flux?
Land/atmosphere flux
Carbon Budget (II)
Land atmosphere flux partitioned as follows
Land use change– From observations
-0.2±0.7
1.7
-1.9
Land atmosphere flux– Must be to balance budget
Residual terrestrial sink Calculated to balance land/atmosphere flux
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?
Video – Global Warming – signs and the science
Explain the concept of ‘ancient sunlight’ and how it relates to the carbon cycle.
Anthropogenic Methane Sources
Leakage from natural gas pipelines and coal mines
Emissions from cattle – Flatulence…gas
Emissions from rice paddies
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…
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
How would you describe the last 30 years of temperature
Ran
dom
Osc
illat
ion
Osc
illat
ion+t
rend
Osc
illat
ion+j
ump
Ran
dom
+jum
p
Tre
nd
0% 0% 0%0%0%0%
1. Random
2. Oscillation
3. Oscillation+trend
4. Oscillation+jump
5. Random+jump
6. Trend
0 of 250
What is the approximate temp trend over the last 30 years?
0 of 250 0
.6C/3
0 ye
ars
1.0
C/30
year
s
.1C/3
0 ye
ars
0.2
C/30
year
s
0% 0%0%0%
1. 0.6C/30 years
2. 1.0C/30 years
3. .1C/30 years
4. 0.2C/30 years
What is the approximate temperature trend over the last 100 years?
+0.
2C/1
0 ye
ars
+0.
5C/1
0 ye
ars
+0.
1C/1
0 ye
ars
0.0
C/10
year
s
0% 0%0%0%
1. +0.2C/10 years
2. +0.5C/10 years
3. +0.1C/10 years
4. 0.0C/10 years
0 of 250