The ozone layer is a precious thing, which helps protect the Earth from the harshest radiation production of the Sun. If there is some damage to this layer, we will all feel the consequences in very short order indeed.
In the past, humanity has worked to limit the damage done to the ozone layer by our own deliberate actions. However, it’s not just aerosol cans and damaged air conditioning systems that are putting it at risk these days. The fierce wildfires we have seen in recent years are also having a negative impact. Let’s take a look at why the ozone layer matters, and how it is being affected by these wildfires.
a protective blanket
The fusion reactor that we call the Sun is a vicious thing. As it collides with hydrogen atoms, combining them into helium, it releases a great deal of heat, light and other electromagnetic radiation. Much of this radiation can be harmful to humans, plants and other organisms.
Thankfully, Earth has an ozone layer to protect it. It is a part of the atmosphere, or stratosphere, to be precise, that has a higher concentration of ozone than the rest of the atmosphere. The difference is actually quite minor – the triple-atom oxygen molecule in the ozone layer is at levels of 10 parts per million (ppm), compared to 0.3 ppm on average seen in the rest of the atmosphere.
Ten out of every million ozone molecules do one important job: blocking about 97–99% of the Sun’s medium-frequency ultraviolet radiation. Without the ozone layer, we would all get sunburned more quickly. In fact, if it were completely gone, plants would cease to photosynthesis, the food supply would dry up, and the Earth’s surface would essentially become sterile in short order.
Although the ozone layer is fragile. A wide variety of man-made chemicals, mainly CFCs, can break down ozone molecules, and give rise to the commonly known hole in the ozone layer that exists today. Due to the important protective nature of the ozone layer, much work has been done on restricting the use of these chemicals and other measures to protect the existence of the ozone layer.
The largest wildfires burn with such heat and intensity that they create huge plumes of smoke that can reach extreme heights, even carrying smoke particles and combustion byproducts into the stratosphere . This is a simple consequence of the fact that hot gases rise up, and wildfires produce a lot of them.
New research has now shown that these compounds can actually change the composition of gases in the upper atmosphere, and potentially even destroy ozone in this atmospheric layer. Scientists used infrared spectrometers on the Atmospheric Chemistry Experiment, a mission operating aboard the Canadian satellite SCISAT, to investigate this issue in the wake of Australia’s tragic 2019/2020 “Black Summer” fires.
Taking spectral measurements of smoke particles in the upper atmosphere, it became clear that the particles contain organic molecules containing oxygen, which can undergo chemical reactions with other molecules in the stratosphere. Further measurements showed increased levels of molecules such as formaldehyde, chlorine nitrate, chlorine monoxide and hypochlorous acid. In turn, a decrease in ozone levels was detected, as well as a drop in nitrogen dioxide and hydrochloric acid levels.
Such a major disturbance in the atmospheric chemistry being studied had not been observed in the past 15 years of satellite measurements. There was a small initial surge in ozone levels after the wildfires, which were suspected to be caused by similar reactions producing ozone pollution at the ground level. However, from April to December 2020, ozone levels fell below the average observed from 2005 to 2019.
In fact, not much can be done to directly fix this problem. Forest fires are already fought on the ground to protect life and limb, as well as property. Getting them out early would help, but firefighters are already doing everything possible in such cases.
However, this is not bad news for the ozone layer. Since the Montreal Protocol outlawed the production of most of the CFC gases that damage the ozone layer, we have seen a gradual recovery from previously human-induced damage. Despite the recent spikes, the hole in the ozone layer is expected to close over the next 50 years. In fact, when NASA checked in 2019, the hole in the ozone layer was the smallest since 1982. However, if major wildfires continue with increasing severity, we could be in more trouble.
In the end, reducing carbon emissions, and halting the pace of climate change, is the best thing we can do to tackle this problem. Reducing global temperatures should help reduce the occurrence and severity of wildfires, and thus less smoke in the upper atmosphere where it is causing such movement.
Title image from ESA’s Sentinel-2 satellite. ESA, Copernicus EMS via Twitter