Pollutionwatch: red sky spells warning when the cause is fire and wood burning

Smoke absorbs purple and blue light, raising alert for air pollution and climate emergencyRed sky at dawn and dusk is part of weather lore and apparently a cause for delight or warning among shepherds and sailors. But, as huge areas of forest burn, the crimson colour of skies over the western US is a red alert for our air pollution and climate emergency. Even in New York and Washington DC the sun turned orange. This is because smoke from wood burning strongly absorbs purple and blue light. Longer wavelengths pass through and the sky takes on shades of red.This curiosity can be useful. In 2005 Swiss scientists noticed that the particle pollution from wood stoves that filled Alpine villages in winter strongly absorbed ultraviolet light, opening a way to routinely measure wood smoke in our air. Continue reading...