GEOG 401 Discussion - Earth Energy Balance - Changing...
Transcript of GEOG 401 Discussion - Earth Energy Balance - Changing...
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GEOG 401 Climate Change
Discussion of Readings Earth’s Energy Balance Changing Atmosphere
Discussion
Readings 1. Diagnosis Earth: The Climate Change Debate, by William
Anderegg 2. The Silver Bullet of Climate Change Policy 3. Climate Change: Who’s the biggest emiMer of them all?
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Diagnosis Earth: The Climate Change Debate, by William Anderegg
• What problem was invesPgated in the study reported here? • What methodology was used? • What were the results? • What are the implicaPons of those results? • Were there any significant flaws in the methodology that
might have biased the results? • When the corporate media presents the issue of climate
change, do you think they fairly represent the scienPfic consensus on global warming?
The Silver Bullet of Climate Change Policy
• What problem does this arPcle address? • What is the “silver bullet of climate change policy according
to this arPcle? • Do you agree or disagree with the conclusions of this arPcle?
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Climate Change: Who’s the biggest emiMer of them all?
• What problem does this arPcle address? • Who are the biggest emiMers? • What is the fairest way to allocate the costs of addressing
climate change?
Energy Balance of Planet Earth
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Energy Balance of Planet Earth Intercepted Solar Energy = solar constant x disk area of Earth Intercepted Solar Energy = 1366 [W m-‐2] x πr2 [m2] Radius of Earth = 6,378,100 meters Intercepted Solar Energy = 1.74575 x 1017 WaMs
Energy Balance of Planet Earth
Intercepted Solar Energy Averaged Over the Whole Earth = Intercepted Solar Energy ÷ Surface Area of Earth = 1366 [W m-‐2] x πr2 [m2] ÷ 4 πr2 [m2] = 1366/4 [W m-‐2] = 341.5 W m-‐2
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Energy Balance of Planet Earth Absorbed Solar Energy Averaged Over the Whole Earth = Intercepted Solar Energy x (1 – Earth Albedo) Earth Albedo = 0.3 Absorbed Solar Energy = 341.5 x 0.7 [W m-‐2] Absorbed Solar Energy = 239 W m-‐2
Energy Balance of Planet Earth To maintain energy equilibrium, the Earth must emit an amount of longwave radiaAon equal to the absorbed solar energy. Earth Longwave EmiDed RadiaAon = Absorbed Solar Energy = 239 W m-‐2
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Energy Balance of Planet Earth What is the mean equilibrium temperature of the Earth?
Use the Stefan-‐Boltzmann equaPon:
Rearranging I = σT4 we get:
T = (I/σ)0.25
T = (239 / 5.67 x 10-‐8)0.25
= 254.8 K
= -‐18.3°C
-‐18.3°C ß RadiaAve Equilibrium Temperature of Earth
Energy Balance of Planet Earth RadiaAve Equilibrium Temperature of Earth = -‐18.3°C
Actual mean surface temperature of earth:
20th Century Mean: 13.9°C (57.0°F)
2012 Mean: 14.5°C (58.03°F)
QuesAon 1: Why is the actual surface temperature 32.8°C higher than the radiaPve equilibrium temperature?
QuesAon 2: Is the radiaPve equilibrium temperature of the earth changing due to increasing greenhouse gases?
QuesAon 3: Why is the surface temperature of the earth increasing?
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Energy Balance of Planet Earth On the following slide is a diagram showing the present-‐day, globally-‐averaged verAcal energy fluxes for planet earth. Look carefully at the diagram and answer these quesAons:
QuesAon 1: How much energy is entering at the earth system at the “top of the atmosphere” (TOA)? Use the mean esPmates.
QuesAon 2: How much energy is leaving at the TOA?
QuesAon 3: Are the incoming and outgoing energy at the TOA equal?
QuesAon 4: Do the same comparison for (a) the atmosphere, and (b) the earth’s surface. Do the comparison using radiaPon only and then do it using all energy fluxes.
QuesAon 5: What will happen to this picture if greenhouse gas concentraPons (a) keep on increasing; (b) level off; (c) decline?
Energy Balance of Planet Earth
AR5 WG1 Drap report (2013, Chapter 2)
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Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
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Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
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Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
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Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
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Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
LSAT Land Surface Air Temperature
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Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
SST Sea Surface Temperature
NMAT Night Marine Air Temperature
Changing Atmosphere
AR5 WG1 Drap report (2013, Chapter 2)
SST Sea Surface Temperature
From Satellites and in situ records