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Physics of Planetary ClimateCors221: Physics in Everyday Life
Fall 2010 Module 3
Lecture 1: Science and Light
What is Climate?
Climate is what you expect;weather is what you get.
-- Robert Heinlein
Climate: composite or generally prevailing weather conditions of a region, as temperature, air pressure,
humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years
Climates of Earth
Climate of Moscow, Idaho
Climate of Moscow, Idaho
The Scientific Method
Observation
Hypothesis
Prediction
Experiment
•Science can not prove a positive;It can only disprove, or prove a negative
#1 Driver of Climate: Sunlight
In order to understand Earth's heating,need to understand light first.
What is light?
Light is the propagation of an electromagnetic disturbance – an electromagnetic wave.
Blackbody Radiation
Lava from Kilauea in Hawaii;molten rock has a temperature of around1000 K – the minimum for visible glowingis 800K.
Blackbody Radiation: Wien's law
Wien's law:
wavelength
b=3000 for T in Kelvin;lambda-max is in microns
Blackbody Radiation
Blackbody Radiation
Total radiated energy, in Wattsper square meter, is proportionalto the temperature to the 4th power!
Can you measure a person'sblackbody emissions?
A camera for light at 10-microns wavelength
Sweet! What else can you dowith tishth ing?
10-micron image
Sweet! What else can you dowith tishth ing?
10-micron image
Sweet! What else can you dowith tishth ing?
10-micron image
Sweet! What else can you dowith tishth ing?
10-micron image
Summary✔ Science can only disprove, not prove✔ Climate is what you expect; weather is what you get✔ Light, all light from radio to gamma rays, is
electromagnetic radiation✔ Shorter, bluer wavelengths have more energy and are
more dangerous than longer, redder wavelengths.✔ All bodies emit blackbody radiation; hotter bodies emit
more ( T4) light and bluer (shorter wavelength) light.✔ Earth cools by radiating infrared light to space by
blackbody radiation