Aerosol pollution: Destabilizing Earth’s climate and a threat to health
by Conrad Fox on 3 March 2022
Mongabay (direct link, with photos and schematic)
- Aerosols are fine particulates that float in the atmosphere. Many are natural, but those haven’t increased or decreased much over the centuries. But human-caused aerosols — emitted from smokestacks, car exhausts, wildfires, and even clothes dryers — have increased rapidly, largely in step with greenhouse gases responsible for climate change.
- Aerosol pollution kills 4.2 million people annually, 200,000 in the U.S. alone. So curbing them rapidly makes sense. However, there’s a problem with that: The aerosols humanity sends into the atmosphere presently help cool the climate. So they protect us from some of the warming that is being produced by continually emitted greenhouse gases.
- But scientists still don’t know how big this cooling effect is, or whether rapidly reducing aerosols would lead to a disastrous increase in warming. That uncertainty is caused by aerosol complexity. Atmospheric particulates vary in size, shape and color, in their interactions with other particles, and most importantly, in their impacts.
- Scientists say that accurately modeling the intensity of aerosol effects on climate change is vital to humanity’s future. But aerosols are very difficult to model, and so are likely the least understood of the nine planetary boundaries whose destabilization could threaten Earth’s operating systems.
China has seen dynasties rise and fall over the last two millennia. Such are the vagaries of human history. But researchers at Trinity College, Dublin, and Zhejiang University, Hangzhou, recently suggested a surprising natural explanation: volcanoes. Of 68 dynastic collapses since 0 AD, they found that 62 were preceded by major volcanic eruptions around the world.
Volcanoes throw tons of tiny particles known as aerosols skyward. These float in the atmosphere with sometimes huge effects: scattering sunlight, absorbing solar radiation, cooling the earth, and changing rainfall patterns. When Mount Pinatubo erupted in the Philippines in 1991, for example, the resulting ash cloud lowered the planet’s temperature by 0.6° Celsius (1.1° Fahrenheit) for at least two years.
The team behind the Chinese dynasty research surmises that volcanic aerosols triggered drought and ruined crops, leading to catastrophic social unrest across China’s agricultural economy. This causality is hard to prove conclusively, but the results suggests just how powerful an effect aerosols may have had on climate and civilization in the past — and today.