I've designed over 40 machines that utilize infrared, ultraviolet or x-ray radiation energy transfer and yes, IT"S THE SUN YOU DUmbasses!!!!!!
Of course its the sun - even the ice cores prove it..
for some 'unknown reason' there is no arctic ice that is much more than 800 years old, which indicates that it had melted away at some time before then. Now, there was no industrialization, the 'new world' was still an unknown quantity, and the earth's population was an estimated 360 million. Yet all the northern ice went away ? How is that even possible ?
The only logical conclusion is the sun has cycles of active and inactive periods beyond the usual 11 year sunspot season that we are just beginning to understand now. The sun isn't a simple linear construct, like a sine wave, but a far more complex organism... example in photographs below..
how mankind regards sunspot activity..

how mankind should regard sunspot activity..

There is a lot that goes on 'behind the scenes' we simply aren't aware of - like a grandfather clock. We see the hands go around and hear the ticking - but have no idea what makes what we see happen. The same can be said about the sun. Its not just a ball of fire, its a complex organism that generates a rich electromagnetic environment, not just heat and the occasional solar flare.