Context

Scientists from the European Space Agency said this week that this rare hole is the largest of its kind ever recorded over the planet’s northern hemisphere. It covers an area about three times the size of Greenland, according to the journal Nature.

The huge hole has been spotted in the Arctic

Causes

Experts point to “unusual atmospheric conditions” as the cause of the massive hole, including freezing temperatures that bring high-altitude clouds together.

  • A powerful polar vortex has trapped especially frigid air in the atmosphere above the North Pole, allowing high-altitude clouds to form in the stratosphere, where the ozone layer also sits.
  • Industrial chemicals interact with these clouds to eat away at the ozone layer
  • By the end of the polar winter, the first sunlight over the North Pole initiated this unusually strong ozone depletion – causing the hole to form.
  • While temperatures consistently plummet in the South Pole each year, these conditions are rare in the North, making ozone depletion much less common.
  • While the newest hole is concerning, scientists say it is expected to heal within the next month as temperatures get warmer. The hole is still nowhere near as worrisome as its southern counterpart and doesn’t currently threaten human health.
  • Using data from the Tropomi instrument on the Copernicus Sentinel-5P satellite, they were able to monitor this Arctic ozone hole form in the atmosphere.

Copernicus Program EU

  • The hole was tracked by the Copernicus Atmosphere Monitoring Service, of the European Centre for Medium-Range Weather Forecasts, based partly in Reading and funded by the European commission.
  • The Tropomi instrument on the Copernicus Sentinel-5P satellite measures a number of trace gases, including aerosol and cloud properties with a global coverage on a daily basis.
  • Upcoming Copernicus Sentinel-4 and Sentinel-5 missions will monitor key air quality trace gases, stratospheric ozone, and aerosols.
  • As part of the EU’s Copernicus programme, the missions will provide information on air quality, solar radiation and climate monitoring.
Polar vortex’ – a circling whirlpool of stratospheric winds.

Ozone Layer

The ozone layer sits in the stratosphere, an atmospheric layer between about 10 and 50 kilometers above the ground, where it protects life on Earth from UV radiation from the sun.

  • Earth’s atmospheric ozone layer acts as a protective barrier between the sun’s harmful rays and the Earth’s surface.
  • Although ozone is present in small concentrations throughout the atmosphere, most (around 90%) exists in the stratosphere, a layer 10 to 50 kilometres above the Earth’s surface.
  • Ozone is measured in what are called Dobson units. The ozone in the atmosphere is about 300 Dobsons.
A Dobson unit of gas is equal to a layer of gas, at the surface of the Earth, with a thickness of one hundredth of a millimeter.

Ozone depletion

Atmospheric concentrations of ozone vary naturally depending on temperature, weather, latitude and altitude, while substances ejected by natural events such as volcanic eruptions can also affect ozone levels.

  • Scientists discovered in the 1970s that the ozone layer was being depleted.
  • Human-made chemicals called chlorofluorocarbons have been destroying the layer for the past century, causing thinning, and eventually, the massive hole that formed in Antarctica in the 1980s.
  • These ozone-depleting substances were mostly introduced in the 1970s in a wide range of industrial and consumer applications, mainly refrigerators, air conditioners and fire extinguishers.

Ozone hole

The severe depletion creates the so-called “ozone hole” that can be seen in images of Antarctic ozone, made using satellite observations.

  • In most years, the maximum area of the hole is bigger than the Antarctic continent
  • Although ozone losses are less radical in the Northern Hemisphere, significant thinning of the ozone layer is also observed over the Arctic and even over continental Europe.
  • Ozone depletion is greatest at the South Pole.
  • It occurs mainly in late winter and early spring (August-November) and peak depletion usually occurs in early October, when ozone is often completely destroyed in large areas
  • Most of the ozone-depleting substances emitted by human activities remain in the stratosphere for decades, meaning that ozone layer recovery is a very slow, long process.

Effects of ozone depletion for humans and the environment

  • Ozone layer depletion causes increased UV radiation levels at the Earth’s surface, which is damaging to human health.
  • Negative effects include increases in certain types of skin cancers, eye cataracts and immune deficiency disorders.
  • UV radiation also affects terrestrial and aquatic ecosystems, altering growth, food chains and biochemical cycles.
  • Aquatic life just below the water’s surface, the basis of the food chain, is particularly adversely affected by high UV levels.
  • UV rays also affect plant growth, reducing agricultural productivity.

Action to protect the ozone layer

The Montreal Protocol

  • In 1987, to address the destruction of the ozone layer, the international community established the Montreal Protocol on ozone-depleting substances.
  • It was the first international treaty to be signed by all countries of the world and is considered the greatest environmental success story in the history of the United Nations.
  • The Montreal Protocol’s objective is to cut down the production and consumption of ozone-depleting substances, in order to reduce their presence in the atmosphere and thus protect the Earth’s ozone layer.

Impact of global action & remaining challenges

Global consumption of ozone-depleting substances has been reduced by some 98% since countries began taking action under the Montreal Protocol.

  • After signing the Montreal Protocol in 1987, 197 countries agreed to phase out chemicals like chlorofluorocarbons in order to protect the ozone from further damage, which has contributed to a decrease in the size of the hole over Antarctica.
  • As a result, the atmospheric concentration of the most aggressive types of ozone-depleting substances is falling and the ozone layer is showing the first signs of recovery.
  • The Antarctic ozone hole was the smallest in 35 years last November, showing the success of efforts to cut the production of the harmful pollutants.
  • In the 2018 Scientific Assessment of Ozone Depletion, data shows that the ozone layer in parts of the stratosphere has recovered at a rate of 1-3% per decade since 2000. At these projected rates, the Northern Hemisphere and mid-latitude ozone is predicted to recover by around 2030, followed by the Southern Hemisphere around 2050, and Polar Regions by 2060.
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