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published on 5 August 2019 in air

Summer wind

A sixteen-year-old Swedish girl is braving the wind, cold and rain to take her protest against the changing climate onto the streets. She does so with large placards on which she writes harsh words with a felt-tipped pen denouncing the seriousness of a global threat and the general lack of concern about it. From 20 August 2018, when Greta Thunberg played truant from school to take her first placard before the Swedish parliament, her plaits and her stern face have become the symbol of a new awareness: climate change is real and is happening now. Greta will take part in the United Nations Climate Action Summit, due to be held on 23 September in New York. She will travel by sailing boat from the United Kingdom to the United States: a symbolic low-impact journey that will take two weeks.

Greta Thunberg protesting outside the Swedish Parliament to urge the adoption of suitable measures against climate change.

The greenhouse effect
A greenhouse is a closed and controlled environment where plants grow at a constant level of temperature and humidity. It is a method of cultivation that cancels the effects of the seasons because the weather within a greenhouse is always fine. The system works because of the transparent glass or plastic roof and walls that trap the heat of the sun inside the greenhouse. The greenhouse effect does something similar: greenhouse gases trap a little solar energy in the atmosphere and heat the planet.

Carbon dioxide is the gas that contributes most to the greenhouse effect (60%), followed by methane (20%), ozone (15%), nitrogen oxides (10%) and chlorofluorocarbons (5%). While carbon dioxide, ozone, methane and nitrogen oxides are for the most part of natural origin, chlorofluorocarbons are artificial; they are gases once used in refrigerators and in spray cannisters and, given that they have caused the famous ozone hole, they were banned in 1990, but they are gases with long life-spans and those that are still in circulation continue to cause damage.

Thank goodness that it exists
When it is hot on Mars, the temperature is 20° below zero. In winter the temperature drops to -120°C: the average is -40°C. Mars has very little air and its atmosphere is not very dense. While here on Earth a cubic metre of air weighs a kilo, on Mars it weighs only 10 grams. Martian water exists but it is frozen or collects in underground salt lakes. Yet once there were rivers and lakes that have left behind clear traces like canyons, valleys and basins, now completely dry. It has not always been so cold on Mars because, before the solar wind swept away the atmosphere, the greenhouse effect heated the surface of the planet enough to melt the ice. Without the greenhouse effect, the temperature on Earth would be -19°C, just a little warmer than that on Mars. Probably, life would not exist here either. So we can give thanks to the greenhouse effect but, as the saying goes, you can have too much of a good thing.

Carbon dioxide concentration over time. Credits: NASA

From the mid-1800s, with the industrial revolution, we began to burn fossil fuels, first coal to drive steam engines, then gas and petroleum; and so the quantity of CO2 in the atmosphere has risen enormously: from 280 to 410 parts per million. Parts per million (PPM) are calculated by taking a sample of air, dividing it into one million parts and measuring how many of these are CO2. 410 PPM may seem like an insignificant quantity, a tiny bubble, but if we consider the vastness of the atmosphere they add up to billions and billions of tons. And then, added to the CO2 of fossil origin is the gas that the trees are no longer able to absorb due to deforestation.

During the last century, due to the greenhouse effect, the average temperature of our planet increased by around one degree Celsius. This may seem to be another negligible increase, but the climate is a very delicate mechanism that depends on very many interconnecting variables: if any of them are altered, there may be unforeseeable consequences. Some consequences, on the contrary, are already clear. The Antarctic has lost over 2500 billion tons of ice, while at the other pole in the frozen Arctic Ocean, during the summer the ice is disappearing even where previously it never melted. The North-West Passage is the legendary and very dangerous route connecting the Atlantic and Pacific Oceans through the frozen Arctic Ocean.

North-West Passage. Credits: Wikipedia

From the mid-16th century up until the beginning of the 20th century, many explorers tried in vain to find a passage through the ice of the North Pole and Alaska, Canada and Greenland: the Spaniard Francisco de Ulloa, sent by Hérnan Cortés, the Englishmen John Davis, William Baffin and Henry Hudson. It is no accident, therefore, that islands, bays, gulfs and rivers in the extreme north are named after these explorers. There was also an Italian, Alessandro Malaspina, who towards the end of the 1700s looked for the Passage for the Spanish monarchy, without success. Over the course of the centuries, the North-West Passage has caused the death of numerous sailors. In 1845, all 128 crew members on board HMS Erebus perished amid the ice floes together with the ship’s captain, Sir John Franklin; only in 2014 did an underwater drone succeed in identifying the wreck and in 2018 the story was made into a hugely successful television series. The North-West Passage was finally conquered by the great Norwegian explorer Roald Amundsen in 1906: 120 years later in the summer of 2016, a cruise ship sailed through it for the first time. It was a luxury voyage for just a few rich tourists: the tickets cost 120 thousand dollars, plus insurance costing 50 thousand more. What was once an impossible destination now welcomes wealthy holiday-makers.

by Andrea Bellati

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