[[!redirects The Color of Night]] +-- {: .standout} This page is a [[Blog articles in progress|blog article in progress]], written by [[Tim van Beek]]. =-- <h4>How to know where does it comes from?</h4> When you measure some infrared radiation coming from the sky, there are two indications why this radiation has to come from "greenhouse gases" in the atmosphere: * It is infrared. Sunlight doesn't have much radiation in the infrared regime. * It is not black body radiation, but is concentrated at the characteristic wavelengths of well known gas components of the atmosphere. Infrared radiation from the surface is to a good approximation black body radiation. Devices to measure the infrared radiation of the planetary surface are called <b><a href="http://en.wikipedia.org/wiki/Pyrgeometer">pyrgeometer</a></b>, for pyr = fire and geo = earth. +-- {: .standout} [[Tim van Beek]]: The following is just a random collection of material right now! =-- * Military Handbook [MIL-HDBK-268(AS)](http://www.google.de/#sclient=psy&hl=de&site=&source=hp&q=MIL-HDBK-268%28AS%29&aq=f&aqi=&aql=&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=485767ee3dfb8252&biw=1121&bih=670) * [Caltech Infrared Spectroscopy](http://www.wag.caltech.edu/home/jang/genchem/infrared.htm) +-- {: .standout} [[Tim van Beek]]: I would like to add radiation measurements, maybe some can be found here: * [Atmospheric Radiation Measurement (ARM) Climate Research Facility](http://www.arm.gov/) Also have a look [here](http://www.eppleylab.com/PrdPrecInfRadmtr.htm). =-- Just to have a number, the flux of DLR (downwards longwave radiation) is about 300 $W m^{-2}$. category: blog