Mega-wildfire has been wreaking havoc in the earth's stratosphere. The stratosphere (strat=layer) is the second layer of the atmosphere, and it is where the ozone layer is located. The ozone layer protects humans, animals, and plants from the Sun's ultraviolet radiation. Life as we know it would not exist without it. Skin cancer and immune system damage risks will likely surge if damaged, so one can imagine what it will do to plants and the rest of the animal kingdom.
Storms and turbulence do not exist in the stratosphere, so cold air is at the bottom of the layer while warm air is at the top—Jet-liners cruise at this altitude. As the climate system changes from human emissions of greenhouse gases, some areas are getting hotter and drier, in particular Mediterranean climates. Under these new conditions, brush and forests can easily ignite from lightning or a tossed cigarette producing massive wildfires where Pyrocumulonimbus clouds are capable of breaking through the stratosphere where they can stay for weeks damaging the ozone layer.
Two recent studies discovered evidence that wildfire is changing the chemistry of the ozone layer.
The research findings were primarily on Black Summer; the jaw-dropping Australian will"fire season in 2019 and 2020
Scientists have recognized threats to the ozone layer from reactive chemicals used in commercial and industrial processes since at least since the 1970s, and have spent a lot of time trying to make sure society understands the chemistry, she said. “This isn’t a new thing to those of us who have been studying it,” she said. “This is not our first rodeo.”
One of the key advances came when scientists started looking at how atmospheric chemistry can be changed by external contaminants like industrial pollution and wildfire smoke, rather than just through internal atmospheric processes.
Solomon said scientists already knew that various pollutants can change atmospheric chemistry at lower altitudes, but were surprised to find reactive particles in the stratosphere.
“We didn’t realize at first how important that could be in the very dry stratosphere,” she said. “The discovery of the Antarctic ozone hole is what woke us up to that fact.”
The Black Summer fires’ depletion of 1 percent of atmospheric ozone, as documented by Solomon and other scientists in a Feb. 28 study in the Proceedings of the National Academies of Sciences, may seem like a small number, she said, but “it’s significant to me because it’s comparable to the 1 percent per decade progress that world has achieved with the Montreal Protocol.”
She said that, while the wildfire smoke’s impacts in the stratosphere don’t last anywhere as long as those from industrial chemical pollutants, the concerns remain because extreme wildfire activity is expected to increase by 30 percent by 2050 and 50 percent by the end of this century.
Old Dominion University Professor Peter Bernath is one of the researchers who have published new evidence in the journal Science that extreme wildfires destroy stratospheric ozone.
"This is the first observation of a new chemistry on the hydrated acidic surfaces of stratospheric smoke particles leading to declining ozone levels," Bernath said. "Large wildfires inject smoke and chemicals produced by biomass burning into the stratosphere where they destroy ozone, which protects us from ultraviolet radiation."
In particular, the research showed the damage to the ozone layer impacts parts of the Southern Hemisphere for about a year. Ozone is constantly produced in the atmosphere, but the wildfires were temporarily able to destroy some ozone, creating an extended period of vulnerability.
These smoke particles produced unexpected and extreme changes in stratospheric gases beyond any seen in the previous 15 years of measurements. For example, relatively unreactive hydrochloric acid has been converted into more reactive chlorine-containing gases such as chlorine monoxide leading to the destruction of ozone at midlatitudes.
Brown carbon aerosol particles are known by their ability to absorb sunlight. This then traps solar radiation within Earth, as opposed to other aerosol particles that reflect it back out to space. Alongside black carbon—caused by the incomplete burning of fossil fuels that can be seen from sources like diesel engines—brown carbon is thought to play an important role in climate change, but there’s still much we don’t know about its relative contributions to it.
This new research, published in the journal One Earth, was five years in the making. In 2017, scientists took the Chinese icebreaker ship Xue Long on a two-month expedition to the Arctic. Once there, they took direct measurements of the atmosphere, focusing particularly on brown carbon emissions that had ended up there.
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“The warming effect of brown carbon in the Arctic was generally ignored in previous climate models,” study author Pingqing Fu, a professor of atmospheric chemistry and biogeochemistry at Tianjin University, told Gizmodo in an email. “By the addition of it, we find that brown carbon can be a strong warming agent in the Arctic, which highlights the importance to manage the wildfires in its surrounding regions in the future.”
Fu and his team now figure that brown carbon’s warming effect in the Arctic is about 30% of that of black carbon’s. About 60% of these emissions come from sources of biofuel burning, including wildfires in the middle and high latitude areas of the world, which release both black and brown carbon into the air. And as the Arctic warms, so do other regions of Earth, setting the stage for an ever-increasing ramp-up of climate disaster.
“The increase in brown carbon aerosols will lead to global or regional warming, which increases the probability and frequency of wildfires. Increased wildfire events will emit more brown carbon aerosols, further heating the earth, thus making wildfires more frequent,” Fu said.
The vicious feedback from wildfire in the Arctic has reduced the sea ice, which means more open water. Open water means more gas and aerosols enter the atmosphere.
From the University of Michigan:
Solid aerosols can change how clouds form in the Arctic. And, as the Arctic loses ice, researchers expect to see more of these unique particles formed from oceanic emissions combined with ammonia from birds, which will impact cloud formation and climate. Additionally, understanding the characteristics of aerosols in the atmosphere is critical for improving the ability of climate models to predict current and future climate in the Arctic and beyond.
"With so few observations, sometimes you get surprises like this when you make measurements. These particles didn't look like anything we had ever seen in the literature, in the Arctic, or anywhere else in the world."
The aerosols observed in the study were up to 400 nanometers, or about 300 times smaller than the diameter of a human hair. Ault, associate professor of chemistry, says that aerosols in the Arctic are typically assumed to be liquid.
Once the relative humidity of the atmosphere reaches 80%—about the level of a humid day—the particle becomes liquid. When you dry the aerosol back out, it doesn't turn into a solid until the relative humidity is about 35%-40%. Because the air over the Arctic Ocean—or any ocean—is humid, researchers expect to see liquid aerosols.
"But what we saw is a pretty new phenomenon where a small particle collides with our droplets when it's below 80% humidity, but above 40% humidity. Essentially, this provides a surface for the aerosol to solidify and become a solid at a higher relative humidity than you would have expected," Ault said.
"These particles were much more like a marble than a droplet. That's really important, particularly in a region where there haven't been a lot of measurements because those particles can eventually end up acting as the seeds of clouds or having reactions happen on them."