Climate
Simple Earth Climate Model
Take-Home Experiment (Grade 10) Write-Up
Background
The Earth gains energy by absorbing radiation emitted by the Sun. Earth also emits energy because all
objects with temperature emit energy in the form of infrared radiation. A measure of the amount of
energy a material can emit is called its emissivity, . An infrared thermometer can be used to measure
the relative emissivity of an object. The temperature an infrared thermometer measures is inversely
proportional to an object’s emissivity.
Results
An infrared thermometer (such as the TN110g available from zytemp
http://www.zytemp.com/Products/tn110g.asp) was used to measure the infrared temperature of
several materials in a physics lab. Some sample results and suggested materials are contained in Table 1.
The outside temperature was held constant by taking all measurements at the same time in the same
room. Attempts should be made to minimize the about of radiation the object is reflecting (as opposed
to emitting) (i.e. place an object such as a sheet of metal perpendicular to most reflective/emissive
surfaces in the room).
Material
Water
White Styrofoam
Cotton
Clear Glass
White Paper
Metal Sink
(Stainless Steel)
Tinfoil
Soil
Tree Bark
Snow
Infrared Temp
(Tobject) (C)
20.5
22.5
23.0
23.0
23.5
24.5
Outside Temp
(C)
23.6
23.6
23.6
23.6
23.6
23.6
Known 
(source shown)
0.981
0.601
0.773
0.923
0.901
0.162
26.5
23.6
0.032
Summary
Low infrared temperatures indicate a high value for emissivity. Metals and shiny objects tend to have
low emissivity and organic and bright objects have high emissivity. Infrared temperatures do not vary
much (compared to emissivity) because the relationship between intensity of emitted radiation and
temperature is actually to the fourth power (P  T4). Thus emissivity ranges from 0-1, but the
temperatures are within a couple of degrees of each other. Known values for emissivity were taken from
the sources below. Values measured at wavelengths of 8-14 m should be used. The emissivity of the
Earth is about 0.9. Do your results support this? Compare organic and non organic materials.
Physics and Astronomy Outreach Program at the University of British Columbia
References
1
http://www.infrared-thermography.com/material-1.htm
2
http://www.infrared-thermography.com/material.htm
3
http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html
Rachel Moll (2009-10-17)
Physics and Astronomy Outreach Program at the University of British Columbia