2/6/14 1 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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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?