Our beautiful planet: Destructive 'mother of pearl' clouds
Melanie Hall
February 4, 2019
Nacreous clouds may be stunning, but they're terrible for the environment. That's because these beautiful whisps of color are wreaking havoc on the ozone layer.
Image: Imago/Zuma
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Casting an iridescent pastel hue across the sky, rare polar stratospheric clouds – also known as nacreous clouds because of their 'mother of pearl' color – are one of the most beautiful of all cloud formations. But they are also the most destructive for the ozone layer.
The phenomenon – which is sometimes mistaken for the Northern Lights – is a contributing factor in forming holes in the ozone layer over the Arctic and Antarctic.
Nacreous clouds form in the world's polar regions in winter, and only exist at high altitudes in the stratosphere, 70,000 feet (21,300 meters) up, in the ozone layer.
They only form when the temperature in the stratosphere is below -78C. This turns any moisture in the air into super-cooled liquid or ice crystals.
While clouds usually don't form in the stratosphere because it is normally too dry for ice crystals to develop, nacreous clouds can be created there because they consist of ice crystals, supercooled water and nitric acid.
Nacreous clouds: beautiful but destructiveImage: picture-alliance/Wildlife/N. Benvie
Their shimmering colors are caused by sunlight diffracting as it passes through the tiny ice crystals, lighting up winter skies.
But despite their beauty, they contribute to the breakdown in the ozone layer, which provides vital protection from the sun's damaging ultraviolet rays.
The ice crystals in the clouds spur on a chemical reaction between the ozone layer and gases such as bromine and chlorine. According to the US' Environmental Protection Agency (EPA), just one atom of chlorine in the stratosphere can destroy more than 100,000 ozone molecules.
Without nacreous clouds, these destructive reactions would be negligible.
Nacreous clouds - seen here over Norway - are becoming more commonImage: Imago/Zuma/H. Baesemann
The prime reason why these destructive gases are in the stratosphere is because of humans using chlorofluorocarbons (CFCs) in products such as refrigerators and aerosol cans.
Although CFCs have been phased out after the 1987 Montreal Protocol, it may take up to another 100 years before the effects of CFCs are reduced in the atmosphere.
Because nacreous clouds only appear when the stratospheric temperatures are below -78C, they are more common in the southern hemisphere because these temperatures are reached more often in the Antarctic than in the Arctic.
As a consequence, the ozone layer is more depleted over the South Pole than over the North Pole.
Manipulating the climate to cool the planet
A new study reveals that the public is very worried about climate manipulation. Climate engineers are testing solar mirrors, cloud whiteners and even sprays that reduce the amount of light that reaches the Earth.
Image: picture-alliance/dpa
Tinkering with temperatures
When we burn fossil fuels we raise the concentrations of greenhouse gases in our atmosphere. That is changing the Earth's climate. Engineers are now able to manipulate the environment, but most test communities have said they don't trust the technology.
Image: AP
Reflecting the sun's rays
Climate engineers say they can launch mirrors into space, angle them towards the sun and stop the sun's rays from penetrating the atmosphere. Less sunlight means less heat being trapped by greenhouse gas - and that means cooler temperatures. But in a recent study, communties in Australia and New Zealand said solar mirrors were too dangerous, expensive and unpredictable.
Image: Meek Tore/AFP/Getty Images
Particles in the stratosphere
Geoengineers have also tested chemical climate control. By launching a tethered balloon into the air and releasing particles into the stratosphere, they say they can turn down the heat. The particles create a global dimming effect and gradually reduce the amount of direct irradiance at the Earth's surface. But test survey participants preferred techniques that make more use of natural processes.
Image: picture-alliance/dpa
Brightening clouds
People have shown less reluctance about cloud brightening. This technique entails spraying seawater into the atmosphere, which changes the size distribution of water drops in existing clouds, making them whiter and thicker. This in turn reflects the sun's rays. But the impact of this on the environment is not well understood.
Image: magann - Fotolia.com
Enhanced weathering
Survey participants also showed less concern about a technique called enhanced weathering. This involves grinding or heating minerals to increase the rate at which they are dissolved by the carbon dioxide in the atmosphere. The limestone which is created traps carbon dioxide for thousands of years. The downside? The process may require a lot of water.
Image: Dave Craw
Absorb CO2 with homemade charcoal
Biochar is charcoal made from vegetation. It locks in carbon dioxide, effectively storing this greenhouse gas for centuries. The problem scientists see is this needs quite a lot of land and right now we need that space for crops. But the public were only moderately opposed to this technique.
Image: picture-alliance/dpa
Action still needed
The survey was carried out by researchers from Massey University in New Zealand and the University of Southampton the United Kingdom. Co-author Damon Teagle told DW that geoengineering is an option, but called for continued action to reduce emissions and improve energy efficiency in order to protect the climate.
