The UV index is not the warm sensation of sunlight on bare skin
3 hours ago
- Sunburn results from DNA damage caused by UV-B (and some UV-A) absorption, not from the sensation of heat.
- The warmth of sunlight is due to visible and infrared light exciting molecular vibrations, which does not directly damage DNA.
- The energy flux of UV-B is hundreds of times weaker than near-IR, so the sun's warmth is unrelated to sunburn rate.
- UV intensity decreases more rapidly than IR away from solar noon, meaning the sun can feel warm in morning/afternoon but pose lower sunburn risk.
- Cloud cover scatters UV and absorbs IR; overcast reduces both, but broken clouds can increase UV intensity at ground level.
- The analysis is based on simulated data from pvlib, with caveats regarding assumptions and model limitations.