What is up with What is up with GW?GW?

(Global Warming)

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Tonight – 10/03Tonight – 10/03 RadiationRadiation EM radiation – universe, Sun, EM radiation – universe, Sun, EarthEarth

Global warmingGlobal warming

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The Two Kinds of Radiation

Electromagnet (EM) radiation – light in all its forms: gamma rays, X-rays, UV, visible, infrared, microwave, radio

Radiation from the decay of radioactive isotopes like U-235. This radiation consists of charged particles (helium nuclei and electrons) and gamma rays. This is the radiation that comes from nuclear weapons

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Electromagnetic Radiation Spectrum

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Everything is always emitting EM (glowing, whether we can see

it or not) because of its temperature

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Black-body Radiation

Black-body radiation is the radiation emitted by an object due to its temperature

The key fact about black-body radiation for us is that its wavelength is inversely proportional to the temperature of the radiator. So the hotter the object, the shorter the wavelength of the radiation it emits

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Cosmic Background Microwave Cosmic Background Microwave Radiation Radiation

NASA 8

Cosmic Microwave Background RadiationCosmic Microwave Background Radiation

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From Oak Ridge National Labs, a US government facility12

Global Warming Speak

Greenhouse effect – the atmosphere is transparent to EM radiation in the visible range. Some of this light coming from the Sun is reflected back into space, but some is absorbed by the Earth’s surface, which re-radiates in the infrared range. The atmosphere is NOT transparent to infrared radiation because “greenhouse gases” absorb these wavelengths and heat up

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Global Warming Speak

Greenhouse effect is good! Mean temperature on the moon is -4 °F at the same distance from sun as Earth because no atmosphere = no greenhouse effect!

Too much greenhouse effect is bad! Mean temperature on Venus is 867 °F because atmosphere is 96.5% CO2! At only ½ the distance from the sun, Mercury’s mean temperature is only 333 °F. 14

What’s the GW What’s the GW misconception?misconception?

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Global Warming Speak

Insolation – short for “incoming solar radiation”. This is the “energy in”.

Albedo – reflectivity. This results in energy out. Higher albedo = more light reflected back into space = more energy out. Snow, ice, and clouds have high albedo, land and oceans have low albedo

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Global Warming Speak

Greenhouse gases – water vapor, CO2, CH4 (methane), etc., i.e. gases that absorb infrared radiation and heat up

Positive feedback – systemic response to a stimulus that reinforces that stimulus. Think “spiraling out of control”. E.g. temperatures go up, melting high albedo glaciers, revealing low albedo ground, more insolation is absorbed, increasing rate of warming

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Global Warming Speak

Negative feedback – systemic response to a stimulus that counteracts the stimulus. Think “stabilizing influence”. E.g. temperature goes up, more evaporation, more high albedo clouds reflecting light into space, temperature goes down. This is a dubious example for a number of reasons

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