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