From ASCII Tweezers · · 1m
UV Index vs Sunlight Warmth
Sunlight warmth doesn't mean sunburn risk.
In brief
Sunlight warmth doesn't mean sunburn risk. The UV index measures sunburn risk while sunlight warmth is a separate sensation from visible and infrared light. Originally reported by ASCII Tweezers.
Why sunburn happens
Sunburn occurs when UV-B light damages DNA, altering its molecular structure without immediate pain.
“DNA UV mutation by Mouagip (derivative of a NASA / David Herring original), released into the public domain”
Why sunlight feels warm
Sunlight warmth comes from visible and infrared light exciting skin molecules, not DNA damage.
UV vs infrared energy difference
UV-B light is hundreds of times less intense than near-infrared light at Earth's surface.
Time of day affects UV differently
UV intensity drops faster than infrared as you move away from solar noon, reducing sunburn risk in morning and evening.
Clouds and sunburn risk
Clouds scatter UV but gaps can amplify UV intensity at ground level, increasing sunburn risk.
How UV index is calculated
UV index uses solar energy models from pvlib to estimate sunlight spectrum at ground level.
“Anderson, K., Hansen, C., Holmgren, W., Jensen, A., Mikofski, M., and Driesse, A. "pvlib python: 2023 project update." Journal of Open Source Software, 8(92), 5994, (2023). DOI: 10.21105/joss.05994”
What it means
The UV index measures sunburn risk while sunlight warmth is a separate sensation from visible and infrared light.
