Buraco na camada de ozônio

Ozone hole at its smallest in 30 years, says NASA’s study

In September 2017, the estimated area was 12.2 million square miles, significantly lower than the average of 16.2 million square kilometers

The ozone hole is shrinking and has reached its smallest size within the past 30 years. In September 2017, the NASA – National Aeronautics and Space Administration –satellites that monitor real-time movements of the ozone layer registered the opening reaching the area of roughly 12.2 million square miles. The uninterrupted reduction of the hole has been happening since 2015, when records were of 14.3 million square kilometers.

It’s still big, to be sure – the ozone hole covers an area about two and a half times the size of the United States – but such reduction is enough to confirm progress in dealing with the problem. First detected in 1985, the ozone hole has never been so small after 1988. Throughout three decades, its average size was 16.2 million square miles.

The methodology adopted for measuring the hole considers the day when the aperture reaches its maximum, by the end of winter in the Southern hemisphere. "The Antarctic ozone hole was exceptionally weak this year. This is what we would expect to see given the weather conditions in the Antarctic stratosphere," said Paul A. Newman, chief scientist for Earth Sciences at NASA, in a statement to the agency.

Why did the ozone layer hole decrease?

Two reasons explain the hole decrease in the ozone layer: weather conditions and the fight against the use of polluting substances.

At the end of 2017, an unstable and stratospheric low-pressure system called Antarctic vortex strongly influenced the hole. This helped minimize polar stratospheric cloud formation in the lower stratosphere, where chlorine- and bromine-catalyzed reactions destroy ozone. According to NASA’s scientists, these conditions enabled restoring the ozone in the lower stratosphere.

Accordingly, the American space agency warns that recent numbers do not represent a short-term remedy for the problems caused by ozone depletion. Levels of ozone-depleting substances like chlorine and bromine remain high enough to produce significant ozone loss.

However, progressive decrease in the hole opening is related to achieving the goals established by the Montreal Protocol, signed by the international community in 1987 and put into operation on January 1, 1989. Its main goal was – and still is – to reduce the use of chlorofluorocarbons, popularly known as CFC gases.

The NASA analysis confirms that, as far as CFC gases are no longer used, the chemical composition for ozone in the stratosphere is less harmful. If goals keep being met, the ozone hole is expected to return to 1980s standards in the early 2070s.

What is the ozone layer and how was the hole formed?

The ozone layer, a 3-millimeter thick membrane, is why there is life on our planet. Thin and fragile, the ozone layer is between 6.2 miles and 25 miles above the Earth's surface and it is exclusively consisted of ozone molecule, composed of three oxygen atoms linked together.

Considered the Earth’s natural sunscreen, it is literally vital. Its layer acts as a global cover reflecting and preventing harmful solar radiation from reaching the surface we live in. All kinds of life that we know, including human, could only develop due to this protection.

This membrane has at least two ruptures, one in each Earth pole. Scientists say there is a moderate opening in the Artic pole, to the north; however, the most worrisome hole is to the south, in the Antarctic pole, above Antarctica.

According to NASA, at the beginning of the 20th century, the hole in the ozone layer was unimpressive, but it has grown over the last 100 years. The reason is the massive use of CFC gases by humans. Now, only human intervention will be able to bring it back to healthy levels.