Tag: What you should know

Emissions of ozone-depleting gases have fallen by 99 Percent

Super fact 41 : Largely thanks to the Montreal Protocol in 1987 the emissions of ozone-depleting gases have fallen by more than 99%, 99.7% to be exact, according to Our World in Data. This has resulted in halting the expansion of the ozone holes and the reduction in emissions of  ozone-depleting gases is saving millions of lives every year.

This is my good news for Earth Day, and it is a super fact. It is a super fact because a lot of people believe that the issue with ozone depleting gases and Montreal protocol is bunk. They take the fact that we are not talking about it much nowadays as evidence that there was nothing to it in the first place. However, they are wrong. We typically don’t talk much about environmental problems that have been addressed successfully. The Antarctic ozone hole that we used to worry about is still there, but its worrisome expansion has been halted.

The Reduction of Ozone-Depleting Gases

The ozone layer, located in the stratosphere, protects Earth from harmful UV radiation. Ozone (O3) is naturally created and destroyed in a balance, but ozone-depleting substances damage the ozone layer by releasing chlorine atoms that catalyze the destruction of ozone molecules.

This problem was discovered by Mario Molina and F. Sherwood Rowland in 1974. They were awarded the 1995 Nobel Prize in Chemistry, along with Paul Crutzen, for their work in atmospheric chemistry. Examples of ozone depleting gases are chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl chloroform ,methyl bromide, carbon tetrachloride, hydrobromofluorocarbons, and chlorobromomethane.

The picture shows the sun radiating UV radiation to earth, which is protected by a blanket of ozone | By 2018 the emissions of ozone-depleting gases had fallen by 99.7 percent
Ozone layer depletion diagram. Earth’s sunscreen, shielding us from the sun’s harmful ultraviolet rays. UV A, B, C. UVA, UVB, UVC.

Ozone depletion causes a breakdown of the ozone layer around the world, including the famous Arctic and Antarctic ozone holes. This allows more UV radiation to reach Earth surface, increasing the exposure to harmful ultraviolet (UV) radiation, which can cause skin cancer, cataracts, and immune system damage.

It also harms plants and marine life, as well as climate. It should be noted that this is a different problem from climate change or if you call it global warming, even though ozone depletion to some degree influence climate change. You can read about climate change related super facts here, here and here.

The Reduction of Ozone-Depleting Gases

The good news is that we have been very successful in reducing ozone depleting gases. The Montreal protocol, a landmark international agreement signed in 1987 to protect the Earth’s ozone layer by phasing out ozone depleting gases, has been very successful.

As you can see in the diagram below from Our World in Data. We have had at least a 99% reduction in ozone depleting gases according to the NASA, the World Economic Forum and the UN Environment Program. More specifically, the reduction is 99.7% by 2018 according to Our World in Data.

Gases visualized in the diagram are CFCs, Halons, HCFCs, Carbon Tetrachloride, Methyl Bromide, Methyl Chloroform. The diagram shows a peak around the end of 1980’s | By 2018 the emissions of ozone-depleting gases had fallen by 99.7 percent
The phase out of six ozone depleting gases. Data source UN Environment Program (2023).

443 million Cases of Skin Cancer Prevented

The NIH estimate that the Montreal Protocol has prevented 443 million cases of skin cancer, 2.3 million skin cancer deaths, and 63 million cases of cataracts in the United States alone. Globally, it is estimated that the Protocol has saved an estimated 2 million people from dying from skin cancer each year.

Yes, you can read that again :

Worldwide the Montreal Protocol has saved an estimated 2 million people from dying from skin cancer each year.

To read more about the Montreal Protocol and the ultimate repair job click here.

The Antarctic Ozone Hole

What about the Arctic and Antarctic ozone holes? Well, they are not gone but they are retreating. When there is an environmental problem, it does not entirely disappear right away even if you remove the root cause. The same is true for global warming. If we succeeded to stop all carbon emissions tomorrow it would take decades for average temperatures to stop rising and hundreds of years for them to come down to “normal”. But remember it would have been much worse without the Montreal Protocol.

There are two graphs. The graph representing the annual mean Antarctic ozone hole is blue. The graph representing the annual maximum Antarctic ozone hole is red. Both graphs are rising initially but after the year 2000 the graphs flatten and even go down a bit.
The graph is from Our World in Data and data comes from NASA Ozone watch 2024.
To see the other Super Facts click here

That Earth is round was well known long before Columbus

Image above by Kevin from The Beginning at Last

Super fact 28: That Earth is round, or spherical (or closely spherical) had been known for at least a couple of thousand years by the time Columbus set sail. Columbus did not set sail to prove that earth was round, and he knew it was round.

Old wooden ship on stormy waters | That Earth is round was well known long before Columbus
How I imagine one of Columbus’ ships. This is a submission for Kevin’s No Theme Thursday

The ancient Greeks, particularly philosophers like Pythagoras and Aristotle knew that earth was round from observing how ships disappeared over the horizon hull first, while their masts were still visible. They noticed the earth’s round shadow cast on the moon during lunar eclipses.

If earth was flat, earth’s shadow would not appear round, especially not all the time. They also noticed that different constellations were visible depending on the location (on earth). So, noticing that earth was round was a simple and obvious observation that easily could be made thousands of years ago.

A photo of spherical earth | That Earth is round was well known long before Columbus
Earth is a sphere, or closely spherical. Photo by Pixabay on Pexels.com.

According to historian Jeffrey Burton Russell, “no educated person in the history of Western Civilization from the third century B.C. onward believed that the Earth was flat.” In 240 BC (2,260 years ago) the Greek mathematician and philosopher Eratosthenes calculated the radius and circumference of earth within an error of 2%.  So why did Columbus want to sail west?

Columbus thought that the earth’s circumference was smaller than what Eratosthenes calculation had shown because he relied on maps created by Ptolemy instead of the calculations made by Eratosthenes. When he landed in the New World it seemed like Columbus had been vindicated but that did not last long. Essentially, Columbus sailed west and discovered America because he miscalculated the earth’s circumference.

The earth globe showing the side with the Pacific Ocean. The Pacific Ocean covers most of this side.
Columbus thought earth was smaller. He did not know about the Pacific Ocean. Earth Pacific Ocean view Stock Illustration ID: 1617553012 by Matis75

It should be noted that even though the earth is very close to being a sphere, it is more correctly an ellipsoid because it is slightly bulging at the equator due to centrifugal forces. You sometimes hear people say that Copernicus or Galileo proposed that earth was round. This is of course false.

Copernicus’s theory of the solar system, the heliocentric model, proposed that the Sun is at the center of the solar system and the Earth, along with other planets, revolve around it. This was not a well-known fact at the time, unlike the fact that the earth is round. Galileo defended Copernicus theory. The famous alleged quote “And yet it moves” / “E pur si muove” is said to have originated from his argument with the church (however, this is not certain).

So, we know that people knew that earth was round thousands of years before Columbus, and thousands of years before the renaissance, and we know that Columbus did not sail west to prove that earth was round, and he certainly did not prove it. Yet I’ve heard this claim quite often, which is why I consider that earth being round being well known long before Columbus a super fact. Too few people believe earth to be flat like a pancake for me to consider earth being round a super fact.

Eratosthenes Calculates the Circumference of Earth

Around 500 BC (2,500 years ago) most Greeks believed that the Earth was round, but they did not know how big it was. The Greek philosopher and mathematician Eratosthenes devised a clever method of estimating its circumference and he got very close. He had heard from travelers about a well in Syene (now Aswan) that at noon on the summer solstice, about June 21 every year, the sun illuminated the entire bottom of a well, without casting any shadows, indicating that the sun was directly overhead. He had also heard that perfectly vertical poles had no shadows at this time.

The reason for this was that Syene/Aswan is located very close to the tropic of Cancer (23.5 degrees versus 24 degrees, or about 60 miles).

In Alexandria, north of Syene, the sun was not directly overhead on the summer solstice. Eratosthenes measured the angle of a shadow cast by a stick at noon on the summer solstice in Alexandria and found it to be 7.2 degrees. Using the distance from Alexandria to Syene and this angle Eratosthenes calculated earth’s circumference to be between 40,250 to 45,900 kilometers. Earth’s circumference is 40,075 kilometers.

On the left a wheel with spokes. On the right there is a sphere and sun rays that hit in two places. One without a shadow and one with a shadow.
Illustration of the measurement of the Earth circumference by Eratosthenes. On June 21st there is no shadow in Syene/Aswan but there is one in Alexandria. Asset id: 2319651251 by Javier Jaime

Resurgence in Flat Earth Beliefs

While very few people believed the Earth was flat 50 years ago, there has been a recent rise in Flat Earth conspiracy theories, largely fueled by online misinformation. Now a day 2% of Americans aged 18-24 years old firmly believe it is flat. That is despite the fact that it is easy to directly observe earth’s round shape. That is a small minority but why would anyone believe such a thing today.

For example, on a flat Earth, a Sun that shines in all directions would illuminate the entire surface at the same time, and all places would experience sunrise and sunset at the horizon at about the same time. With a spherical Earth, half the planet is in daylight at any given time and the other half experiences nighttime. Well just give someone overseas a phone call and you’ll see what the case is. In addition, different places have different amounts of daylight at the same time, which wouldn’t happen with a flat earth.

You can observe the round shape from an airplane. If you stand on a hill by the coast, you can see ships disappearing over the horizon hull first, and you can see earth’s round shadow cast on the moon during lunar eclipses. If you travel far, you can see the constellations and the stars being in different positions in the sky. The southern and northern hemisphere have completely different constellations.

Never mind Eratosthenes, gravity, the Coriolis force, other celestial bodies being round, eyewitness accounts by astronauts, ring-laser gyroscopes, and Foucault pendulums. The moon shows the same face to everyone on earth, which would not be possible if earth was flat. Also never mind NASA photos and the fact that no one has found the earth’s edge.

Below is a youTube video showing an animation composed of actual satellite photos by NASA. Earth is obviously round in this video.

In this video the near side of the moon is dark and what you see is the far side. The far side looks a little bit different from the near side of the moon. It is a new moon and the people on earth don’t see the moon. The sun is behind us and lights up both earth and the far side of the moon (this side people on earth do not see). Also, since there is daylight, the camera does not capture faint objects such as stars.

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