I wanted to know what's is the intensity of terrestrial radiation? I mean the long wave radiation emitted by Earth & its atmosphere. As, I was differentiating between solar radiation and terrestrial radiation and intensity is the major thing to know when differentiating between these.

  • $\begingroup$ Hello, and welcome to Stack Exchange. Are you asking for a definition of the term, or an actual value (I'm sure in real life it varies drastically)? $\endgroup$ Apr 21, 2016 at 12:02
  • $\begingroup$ Do you mean the radiation (e.g. infrared) from the earth into the space? $\endgroup$ Apr 21, 2016 at 12:17
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    $\begingroup$ It always starts with xkcd: xkcd.com/radiation $\endgroup$
    – Jan Doggen
    Apr 21, 2016 at 13:25
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    $\begingroup$ Please clarify what you mean by terrestrial radiation. The NRC, in the USA, defines it as natural background radiation emitted by radioactive materials such as thorium, uranium & radon (ie ionizing radiation). But another source defined it as long wave radiation emitted by the Earth & its atmosphere, which is totally different to shortwave ionizing radiation. $\endgroup$
    – Fred
    Apr 21, 2016 at 14:21
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    $\begingroup$ Wouldn't this be equal to the heat generated within the earth? Assuming you don't mean energy absorbed and re-emitted from solar radiation (possibly at different wavelengths). With conservation of energy, the terrestrial radiation will be equal to the generation. $\endgroup$
    – haresfur
    Apr 22, 2016 at 0:51

2 Answers 2


Assuming your question is about how much of the sun's radiation hits the Earth's surface rather than just reaching the edge of the atmosphere ...

The amount of solar radiation that hit's the Earth's surface varies a lot, depending on weather conditions, time of day, day of the year, latitude, altitude, air quality ... It can be anywhere between 0 and ~$1200W/m^2$

There is a standard "full sun" solar intensity which is used as a benchmark for things like photovoltaics testing and calibration. That's $1000W/m^2$, with an atmospheric spectrum denoted by AM1.5


Heat Flux from the earth is about 47 TW +/- 2 TW

Davies,J.H.,Davies,D.R.,2010.Earth’s surface heat flux.Solid Earth 1,5‐24.

A very detailed breakdown of the origin of the heat flux is in this paper. http://arxiv.org/abs/1111.6099

There is a discrepancy of about 20 TW that can't be completely explained by known or legacy heat sources within the earth. My father and I suggest in our book Terrestrial Nuclear Processes http://www.createspace.com/3823397 the discrepancy is possibly explained by low energy nuclear reactions in the crust and upper mantle.


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