Menu
• • ← →

Causes: Ozone O3

The ozone hole over Antarctica 2020 (larger) & 2025 (smaller) – Image: NASA Earth Observatory

  Causes

Home > Climate wiki > What causes climate change? > Greenhouse gases > Ozone

Ozone O3

Summary

  • Ozone in the lower atmosphere (troposphere)(Fig. 1) is a greenhouse gas that absorbs some infrared energy from Earth, re-radiating it into the atmosphere. Due entirely to the way it chemically interacts with man-made emissions—including methane, nitrous oxide, and carbon monoxide—because ozone is a short-lived gas, its concentration varies enormously in different places, times, and seasons.
  • Ozone in the upper atmosphere (stratosphere)(Fig. 1), protects the DNA of plants and animals from harmful solar radiation. Without it, life on the surface of the Earth wouldn’t exist. The Montreal Protocol aims to protect the ozone layer by phasing out the use of man-made chemicals (CFCs) that deplete it. This has helped prevent large quantities of carbon dioxide in plants and soils from being released into the atmosphere, which would have resulted in even more warming:

The avoided ultraviolet radiation and climate change also have co-benefits for plants and their capacity to store carbon through photosynthesis…we estimate that there could have been 325–690 billion tonnes less carbon held in plants and soils by the end of this century (2080–2099) without the Montreal Protocol (as compared to climate projections with controls on ozone-depleting substances). – Young et al, 2021

Ozone depletion is not only a serious health threat but can also affect the climate. Atmospheric chemistry models reveal that springtime Arctic ozone depletion can have major consequences for the seasonal climate in the Northern Hemisphere, including warming over Eurasia and drying across central Europe. – Nature Geoscience Article 07 Jul 2022

  • This underscores the point that greenhouse gases are not inherently ‘bad’. Rather, that human activities have and continue to change the balance of gases in the atmosphere, causing a complex array of problems for life on Earth.

The South-Eastern Australian bushfires 2019-2020 released smoke particles into the Earth’s upper atmosphere that contributed to the highest recorded temperature in the lower stratosphere since the early 1990s, and could have extended the lifetime of the Antarctic ozone hole. – Damany- Pierce et al, 2022

Every 16 hours, a Starlink satellite falls out of the sky…Every Starlink that burns up dumps about 30 kg of aluminum oxide into the upper atmosphere…That aluminum is not supposed to be there…It all adds up to a giant uncontrolled experiment in atmospheric chemistry. Researchers already know that aluminum oxides can destroy ozone in a complex series of steps involving Al₂O₃, HCl, AlCl₃, sunlight, Cl, and O₃. Other side-effects may reveal themselves in time. –  Spaceweather.com, April 2026

  Causes

Home > Climate wiki > What causes climate change? > Greenhouse gases > Ozone

Summary

  • Ozone in the lower atmosphere (troposphere)(Fig. 1) is a greenhouse gas that absorbs some infrared energy from Earth, re-radiating it into the atmosphere. Due entirely to the way it chemically interacts with man-made emissions—including methane, nitrous oxide, and carbon monoxide—because ozone is a short-lived gas, its concentration varies enormously in different places, times, and seasons.
  • Ozone in the upper atmosphere (stratosphere)(Fig. 1), protects the DNA of plants and animals from harmful solar radiation. Without it, life on the surface of the Earth wouldn’t exist. The Montreal Protocol aims to protect the ozone layer by phasing out the use of man-made chemicals (CFCs) that deplete it. This has helped prevent large quantities of carbon dioxide in plants and soils from being released into the atmosphere, which would have resulted in even more warming:

The avoided ultraviolet radiation and climate change also have co-benefits for plants and their capacity to store carbon through photosynthesis…we estimate that there could have been 325–690 billion tonnes less carbon held in plants and soils by the end of this century (2080–2099) without the Montreal Protocol (as compared to climate projections with controls on ozone-depleting substances). – Young et al 2021

Ozone depletion is not only a serious health threat but can also affect the climate. Atmospheric chemistry models reveal that springtime Arctic ozone depletion can have major consequences for the seasonal climate in the Northern Hemisphere, including warming over Eurasia and drying across central Europe. – Nature Geoscience 2022

  • This underscores the point that greenhouse gases are not inherently ‘bad’. Rather, that human activities have and continue to change the balance of gases in the atmosphere, causing a complex array of problems for life on Earth.

The South-Eastern Australian bushfires 2019-2020 released smoke particles into the Earth’s upper atmosphere that contributed to the highest recorded temperature in the lower stratosphere since the early 1990s, and could have extended the lifetime of the Antarctic ozone hole. – Damany-Pierce et al 2022

Every 16 hours, a Starlink satellite falls out of the sky…Every Starlink that burns up dumps about 30 kg of aluminum oxide into the upper atmosphere…That aluminum is not supposed to be there…It all adds up to a giant uncontrolled experiment in atmospheric chemistry. Researchers already know that aluminum oxides can destroy ozone in a complex series of steps involving Al₂O₃, HCl, AlCl₃, sunlight, Cl, and O₃. Other side-effects may reveal themselves in time. –  Spaceweather.com, April 2026

Layers of the atmosphere to show where the ozone layer sits
Figure 2: The protective ‘Ozone Layer’ in the Stratosphere 20-30km above the surface of the Earth protects living organisms on the surface from harmful radiation. However, when ozone is down near the surface of the Earth in the Troposphere, it’s both a powerful greenhouse gas and pollutant. (Image: UCAR Centre for Science Education)

Ozone is present in two different areas of the atmosphere and plays two different roles. It is produced naturally in the outer layers of the atmosphere (the stratosphere) very high above earth. This stratospheric ozone helps protect the planet from the Sun’s ultraviolet rays which can damage our skin and health. This ozone is typically known as the ozone layer.

Although ozone is vital in the stratosphere, here at the Earth’s surface it is a pollutant which can damage our health and the environment.

At the Earth’s surface, ozone is not directly emitted but is formed by reactions of other pollutants such as nitrogen oxides and volatile organic compounds (VOCs), and sunlight. This is known as a photochemical reaction and often produces photochemical smog.

The primary pollutants are produced mainly from motor-vehicle emissions and other combustion sources, and industrial and domestic use of solvents and coatings.

Auckland, Hamilton and Christchurch have the highest potential for ozone pollution. – NZ Ministry for the Environment

A giant atmospheric chemistry experiment

Every 16 hours, a Starlink satellite falls out of the sky. It’s part of the SpaceX business model: Old obsolete satellites re-enter to make way for newer models. This may sound like a good way to keep Earth orbit from becoming too cluttered, but it comes with a cost. Every Starlink that burns up dumps about 30 kg of aluminum oxide into the upper atmosphere.

That aluminum is not supposed to be there. 

The following is histogram of Starlink re-entries is updated daily on Spaceweather.com [see the right column]

Number of Starlink satellites reentered the atmosphere

So far this year (April 28, 2026), 171 Starlinks have reentered, adding more than 5 metric tons (5,000 kg) of aluminum oxide to the stratosphere and mesosphere. How does this compare to natural sources?

The primary natural source is meteoroids – the same “shooting stars” that streak across the night sky. As they burn up between roughly 75 and 110 km, they release a faint dusting of metals. Recent studies suggest that meteoroids disperse between 40,000 kg and 58,000 kg of Al₂O₃ into the atmosphere each year. Starlink in 2026 is on track to add between 26% and 39% of that natural total.

39% may not sound too bad, but consider the following: The size of the Starlink constellation is rapidly increasing, and SpaceX’s competitors are racing to catch up. A full buildout of planned megaconstellations with corresponding re-entries could inject more than 360,000 kg of Al₂O₃ per year – a 640% excess above natural meteoroids (Ferreira et al. 2024).

It all adds up to a giant uncontrolled experiment in atmospheric chemistry. Researchers already know that aluminum oxides can destroy ozone in a complex series of steps involving Al₂O₃, HCl, AlCl₃, sunlight, Cl, and O₃. Other side-effects may reveal themselves in time. –  Spaceweather.com.

More information