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


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?


AR5 WG1 Drap report (2013, Chapter 2)

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Changing Atmosphere


Changing Atmosphere


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Changing Atmosphere


Changing Atmosphere


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Changing Atmosphere


Changing Atmosphere


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Changing Atmosphere


Changing Atmosphere


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Changing Atmosphere


Changing Atmosphere


LSAT Land Surface Air Temperature

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Changing Atmosphere


SST Sea Surface Temperature

NMAT Night Marine Air Temperature

Changing Atmosphere


SST Sea Surface Temperature

From Satellites and in situ records

GEOG 401 Discussion - Earth Energy Balance - Changing...

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