My understanding is that it is difficult to measure the amount of radiation the earth receives to the sun and that due to variability in a number of different quantities such as the changing distance to the sun, the tilt of the earth, and the variable amount of radiation emitted from different parts of the sun's surface, it is not currently possible to measure solar irradiance. Is this correct?
$\begingroup$ Yes you can measure it. See ngdc.noaa.gov/stp/solar/solarirrad.html $\endgroup$– f.thorpe ♦May 1, 2017 at 1:41
1$\begingroup$ No, it is not correct. Solar irradiance is measured by satellite instruments (to avoid errors due to clouds, dust, &c), and has been since the 1970s. This link has a graph, and a discussion on problems with things like reconciling measurments from different satellites: earthobservatory.nasa.gov/Features/VariableSun/variable2.php $\endgroup$– jamesqfMay 1, 2017 at 5:00
2$\begingroup$ Your understanding is incorrect. My first job out of college involved the Solar Backscatter Ultraviolet / Total Ozone Mapping System experiment on NASA's NIMBUS-7 satellite. Just down the hall, others were working on the Earth Radiation Budget experiment on the same satellite. We've been measuring the Sun's output since the late 1970s. $\endgroup$– David HammenMay 1, 2017 at 10:37
$\begingroup$ "WHICH" radiation -infrared -UV -Gamma? Since the suns output will vary by time, Satellites do the job of monitoring solar irradiance. $\endgroup$– LazyReaderSep 30, 2021 at 5:43
Your understanding is half correct. Yes, we can measure the amount of radiation the Earth receives from the Sun.
Yes, it is difficult to get an extremely precise measure of how much radiation the Earth receives from the Sun in any one time interval. But there's not really much value in such extreme precision anyway.
However, it is fairly easy to measure solar irradiance at any one place (on earth, in the atmosphere or in space); as NASA and others currently do (kudos to farrenthorpe for the link). These measurements account for the changing distance to the sun, and the tilt of the earth, and to a very large extent the variable amount of radiation emitted from different parts of the sun's surface, because the Sun's diameter is tiny compared to the distance between the Earth and the Sun (just under 1%).
And having measured solar irradiance at one or more places, it is then easy to get a fairly precise estimate of how much radiation the Earth receives from the Sun in any one time interval.
$\begingroup$ This does not answer the question because it does not describe the way in which solar irradiance of the earth is measured. $\endgroup$ May 1, 2017 at 9:32
4$\begingroup$ Your question does not ask how it is measured: but I take it from your comment that that is what you intended to ask - is that correct? $\endgroup$– 410 goneMay 1, 2017 at 11:06