A critical look at surface-air-temperature change: Influencing ground-level ozone or not is the question

Ozone (O₃) is a colorless but not odorless gas. When ignited, ozone gives off a chlorine-bleach-like odor. So, obviously, based on this, there is a point at which ozone ignites, and it is when this ignition point is reached that the chlorine-bleachish smell from the ozone is produced and released. It is in this sense that temperature has a direct influence on ozone when the change in is such that it becomes high enough to cause a change in the way ozone in this particular instance behaves.

In the stratospheric layer high above the earth’s surface, ozone is an asset in that it prevents much of the ultraviolet (UV) radiation coming from the sun from reaching Earth’s surface. When it was discovered that stratospheric ozone was being destroyed by ozone-depleting substances here on Earth that made their way to the stratosphere and eventually caused a gaping hole to open up over the Antarctic region, this became tremendous cause on Earth for concern. The problem having been identified and addressed, that hole is now diminishing in size and integrity to stratospheric ozone is being restored.

Ozone on the ground or in the tropospheric layer is a completely different story. This is the so-called “bad ozone,” the kind that when inhaled causes damage to human health. Due to ozone’s corrosive nature, it more or less burns away the delicate tissue in the lungs. This ozone type can trigger asthmatic responses in some while in others can cause wheezing, coughing, chronic obstructive pulmonary disease (COPD) and worse in others, and can even lead to death.

In combatting the scourge that ozone is, what is extremely helpful is having an understanding of how ozone forms in the troposphere, what facilitates its perpetuation and best way to approach it in terms of its mitigation and possibly ozone’s complete ground-level elimination.

In regard to ozone’s atmospheric or tropospheric creation, there are three contributing factors enabling its formation, these being chemical, light and temperature.

Chemical: The chemical components of ozone are: hydrocarbons (HC) and oxides of nitrogen (NOx). The mixing of these so-called ozone-forming chemicals in the presence of sunlight and, yes, heat, prompts ground-level ozone formation.

Sunlight: Light from the sun is a huge determining factor. This is the reason why ozone and consequently smog is problematic in daytime only – when the sun is shining. On the other hand, when the sun is absent from the sky, smog is likewise.

Temperature: The phenomenon that ozone is, well, it’s also a warm-weather driven, which is why ozone isn’t evident when the air temperature drops below a certain threshold.

While humans can control the ozone precursor chemical inputs, what are out of the control of humans are the contributing sunlight and temperature factors.

More food for thought

What we want to concentrate on next is the temperature or more precisely the temperature change component as a potential influencer on a changing atmospheric ozone picture.

Okay, so check this out: “Unless offset by additional emissions reductions of ozone precursor emissions, there is high confidence that climate change will increase ozone levels over most of the United States, particularly over already polluted areas, thereby worsening the detrimental health and environmental effects due to ozone. The climate penalty results from changes in local weather conditions, including temperature and atmospheric circulation patterns, as well as changes in ozone precursor emissions that are influenced by meteorology. Climate change has already had an influence on ozone concentrations over the United States, offsetting some of the expected ozone benefit from reduced precursor emissions. The magnitude of the climate penalty over the United States could be reduced by mitigating climate change,” is the opening paragraph of the “Executive Summary” of Chapter 13: “Air Quality” in the Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II document.¹

But what exactly should be made of or taken away from this?

So, in the next section, “State of the Sector,” under the “Key Message 1: Increasing Risks from Air Pollution” subheading, there is this qualifying statement: “Although competing meteorological effects determine ozone levels, temperature is often the largest single driver.”²

Temperature as atmospheric ozone-concentration driver, and “the largest single driver” at that, hmmm!

And there is this qualifying statement: “Assessments of climate change impacts on ozone trends are complicated by year-to-year changes in weather conditions and require multiple years of model information to estimate the potential range of effects.”³

Okay, so we know that meteorology and chemicals play a role in the formation of ground-level ozone. But climate change – how exactly does this factor in?

It would appear that the climate is changing, this change seems to have prompted a change in air circulation patterns and indications are that fossil-fuel-burning activity is a driver, though how much of a driver is not known definitively. What is known definitively is that the average temperature at the surface of the earth has changed: It’s been increasing. Since 1800 there has been a 1.9 degree Fahrenheit increase. It has also been established that 2011 to 2020 is the warmest decade on record. The sea-ice extent in the Arctic is smaller.

Established also, according to the same source, is increasing durations of drier weather.⁴ Longer periods of hotter temperatures could mean increased opportunity for daily ozone (smog) formations. As can be seen, though, this is more about weather than it is about climate.

Expanding on that, what with the hotter summer temperatures covering a broader swath, add in a sufficient amount of ozone precursor emissions in the atmosphere, there could be more and more locations – big cities, small towns, rural tracts – that become smog-impacted whereas that might not have been the case otherwise.

If there was ever a question as to there being a surface-air-temperature-change-ground-level-ozone-influencing connection, any doubt about that can now be removed. Hopefully, further clarity has been brought to this whole notion of surface-air-temperature-change-as-ground-level-ozone influencer.

And now, with any luck, the statement: “concomitant with a rise in average ambient air temperature at the earth’s surface, in this air, coming also is a corresponding jump in pollution,” the one we saw in “Scientific analysis: Facts-driven. Any questions?!” has way more meaning.

Notes

1. Christopher Nolte et al., U.S. Global Change Research Program, Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II, “Chapter 13: Air Quality,” 2018, p. 514. Available at: https://nca2018.globalchange.gov/downloads/NCA4_Ch13_Air-Quality_Full.pdf
2. Ibid, p. 519
3. Ibid
4. Ibid, p. 514

Image above: AndrewHorne

This post was last revised on Dec. 25, 2020 @ 8:05 a.m. Pacific Standard Time.

Published by Alan Kandel