How Haze Particles Affect Climate
Burning Fossil Fuels Produces Changes in Clouds, Precipitation
What is Haze?
When fossil fuels are burned, haze particles are produced in the atmosphere. These particles, also known as aerosol particles, can both reflect and absorb sunlight, causing abnormal changes in the atmosphere. This is referred to as the aerosol direct effect. The degree of these changes is still uncertain.
The College of Oceanic and Atmospheric Sciences (COAS) at Oregon State University studies haze pollution affects on climate change. According to COAS scientists, haze particles in the atmosphere “shade the Earth’s surface”. Cooler temperatures at the Earth’s surface result from this reduction in sunlight.
Yet, many variables surround the production of haze and its effect on climate. The concentration of haze particles depends very much on how the byproduct is produced. Sources of haze include:
- Industry
- Vehicles such as cars and trucks, burning fossil fuels
- Forest fires, used to clear land
- Natural causes such as dust storms and volcanoes
Weather conditions during production can also determine haze particle concentration. Haze particles only persist for up to a week. These particles can be removed from the air by precipitation.
Pollution Effect on Clouds
Clouds are made up of small droplets, as water condenses on tiny particles. Pollution such as haze can change the particles within clouds. Once haze particles enter clouds, they increase the number of cloud droplets. The haze creates more opportunity for water to condense around these particles. These clouds contain more, smaller sized droplets. This interaction is important because clouds with a larger number of droplets, reflect more sunlight. This interaction is referred to as the aerosol indirect effect.
Scientists Observe Ship Tracks
One way scientists have been able to observe this change in clouds is by observing ship tracks. COAS scientists learn how clouds respond to haze pollution by observing marine clouds. Using NASA satellite observation, the scientists watch as these clouds respond to pollution by ocean-going ships on the West Coast. Pollution from the ships interacts with the clouds directly above the flume of pollution. As the haze particles enter the clouds, the plume becomes smaller.
The COAS scientists have found consistencies with climate model models showing the effects of pollution on clouds. Polluted clouds result in holding more water than those not affected. However, they have concluded that the effect may not “be as large as predicted by models”, proving that haze particle effects on climate, remain ambiguous.
Haze Reduces Evaporation
One of the main effects of haze is a reduction in evaporation. This causes changes in precipitation for the region directly below the concentrated haze and adjacent areas. A 2002 study by the American Meteorological Society, focusing on the effects of haze on the South Asian monsoon, found the effects on evaporation to be rather large. Haze affected areas experienced increased precipitation. In result, as evaporation over the ocean was suppressed, this led to decreased concentration of precipitation in all other areas.
Sources:
Oregon State University College of Oceanic and Atmospheric Sciences
American Meteorological Society
Scientists Observe Ship Pollution Effects
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