Industrial aerosols contribution to global cooling

Industrial aerosols contribution to global cooling

Subject : Environment

Section :Pollution

Context: How much do industrial aerosols contribute to global cooling? New study offers clues.

More on the News:

• Inactive volcanoes contributed 66 per cent of sulphate emissions, known to cool the planet, in the preindustrial era, suggesting they were more abundant than previously estimated, a new study reveals.
• Sulphate emissions can be traced back to natural sources such as volcanoes and industrial processes, including oil combustion, traffic emissions and coal burning.
• Sulphur dioxide, released from natural as well as anthropogenic sources, reacts with water vapour and other gases in the atmosphere to create sulphate aerosols.
• They can cool the planet by reflecting sunlight into space, according to the United States National Aeronautics and Space Administration. They also form clouds, which also tend to have a cooling effect.
• A higher abundance of sulphate aerosols in the preindustrial atmosphere means anthropogenic sulphate has a relatively small cooling effect.
• Previous studies estimated that the amount of sulphur dioxide released by volcanoes is smaller than by anthropogenic sources.
• Climate models do not consider hydrogen sulphide, which escapes from inactive volcanoes. These gases react with oxygen to produce sulphur dioxide within three days, forming sulphate aerosols.
• The new study estimates hydrogen sulphide emissions from volcanoes, suggesting that this gas was likely to contribute to atmospheric sulphate in the preindustrial era significantly.
• The team also wants to investigate sulphur emissions from other sources, such as phytoplankton (tiny marine algae). Marine phytoplankton emits dimethylsulphide, an organic sulphur-containing compound that produces sulphur aerosols.

Aerosol

• Aerosols are defined as a combination of liquid or solid particles suspended in a gaseous or liquid environment.
• “Primary” aerosols, like dust, soot, or sea salt, come directly from the planet’s surface. They get lifted into the atmosphere by gusty winds, shot high into the air by exploding volcanoes, or they waft away from smokestacks or flames.
• “Secondary” aerosols form when different things floating in the atmosphere like organic compounds released by plants, liquid acid droplets, or other materials—crash together, culminating in a chemical or physical reaction.
• Aerosols come from both natural and human sources.
• Natural sources of aerosols include sea salt generated from breaking waves, mineral dust blown from the surface by wind, and volcanoes.
• Anthropogenic aerosols include sulfate, nitrate, and carbonaceous aerosols, and are mainly from fossil fuel combustion sources.

About Aerosols:

• Aerosols are a mixed bag of substances, liquid and solid, that differ from their gassy brethren.
• They tend to hang in the atmosphere near their source, or move as localised or regional masses via air currents.
• They range in size from a few atoms across to the width of a human hair.
• They include:
  • crystals of sulphate,
  • balls of almost pure black carbon (commonly, though not entirely accurately, called soot),
  • droplets of nitric or sulfuric acid, spores of pollen.
• They may be salt freed from the crests of breaking waves, or desert sand whipped up by the wind.
• Natural Aerosols: One of the largest natural sources of aerosols are plankton, which breathe out dimethyl sulphide (DMS), a strong-smelling chemical that gives the sea it’s familiar pungent odour.
  • DMS reacts with oxygen to produce clouds of sulfuric acid.
  • Sulphur dioxide released by volcanoes does the same.
• Ninety percent of aerosols in the atmosphere are naturally occurring, but their levels have remained relatively constant over time.
• Anthropogenic Aerosols: On the other hand anthropogenic, or human-made aerosols are emitted from:
  • vehicle exhausts;
  • the smokestacks of factories,
  • ships and coal-burning powerplants;
  • by farmers burning field stubble and land grabbers clearing Amazon forest with fire;
  • by gas flares on oil rigs and discarded plastic shopping bags.
  • Even tumble driers release microplastic fibres that float skyward.
• These sources have increased dramatically over the industrial period, roughly in step with greenhouse gases.
• Most aerosols help cool the planet by reflecting sunlight back out into space, reducing the amount of radiant energy that reaches Earth’s surface.
• They also help create clouds or brighten existing clouds, by acting as condensation nuclei around which water vapor condenses.
• Aerosols first came to public attention in the 1970s, not so much because of their cooling impact, but due to acid rain.
• The worst aerosols are very fine particulates that can penetrate deep into the lungs and may even enter the blood stream exacerbating respiratory and cardiovascular conditions.