Wildfires are a major source of air pollution. They are also predicted to worsen as climate change progresses.
This bleaching process is heavily dependent on atmospheric conditions, which vary across regions. The longer it takes for brown carbon to become white, the greater an impact it can have on the environment. Aerosol particles are everywhere and have a large effect on both health and the climate. When aerosol particles interact with light, a portion of the light is absorbed but the rest reflects and scatters off of the particles.
Aerosol particles from smoke contain brown carbon. The various molecules that make up brown carbon are similar to some organic dyes, overall giving it a characteristic brown colour. However, when ozone in the atmosphere reacts with brown carbon, it can transform it into new colourless molecules that do not warm the earth.
This is because temperature and humidity change the viscosity of aerosol particles. Humid conditions lead to a lot of water getting absorbed into the particles, and as a result they become very fluid. But if that water is removed and the aerosols get cold, they become very viscous, like molasses — or even glass in extreme conditions.
Atmospheric modelling The result is significantly different when we put this new, longer-lasting brown carbon into an atmospheric model that simulates the transport of aerosols around the planet and how they interact with solar radiation. The new results show a warming effect on the climate from brown carbon that is twice that of the previous estimate.