by Daniel Brouse and Sidd Mukherjee

Abstract

Lightning is one of the most important natural sources of nitrogen oxides (NOx) in Earth’s atmosphere and plays a significant role in the formation of tropospheric ozone (O3). While ozone is often discussed primarily as an air pollutant and greenhouse gas, its impacts extend far beyond atmospheric chemistry. Ozone damages vegetation, reduces carbon sequestration, weakens ecosystem resilience, and may contribute to self-reinforcing climate feedbacks. At the same time, climate warming is projected to increase atmospheric moisture, thunderstorm intensity, and lightning activity, potentially creating additional ozone production. This paper examines the mechanisms by which lightning generates ozone, the climatic and biological consequences of ozone formation, and an expanded Earth-system feedback framework linking warming, lightning, ozone, vegetation productivity, carbon sink degradation, and wildfire activity.

Introduction

Ozone occupies a unique position within Earth’s climate system.

In the stratosphere, ozone protects life by absorbing harmful ultraviolet radiation. In the troposphere, however, ozone acts as a powerful oxidant, a greenhouse gas, and a biological toxin.

Although fossil fuel combustion remains the dominant source of anthropogenic ozone precursors, lightning represents one of the largest natural sources of atmospheric NOx and therefore plays an important role in ozone production throughout the middle and upper troposphere.

Traditionally, lightning-generated ozone has been viewed primarily through the lens of atmospheric chemistry. Increasing evidence suggests that a broader Earth-system perspective may be warranted because ozone simultaneously affects climate, ecosystems, carbon cycling, wildfire vulnerability, and atmospheric composition.

Lightning as a Natural Ozone Generator

Lightning generates tropospheric ozone through two primary mechanisms.

Thermal Production of Nitrogen Oxides

A lightning channel can briefly reach temperatures approaching 30,000°C (approximately 50,000°F), making it hotter than the surface of the Sun.

These extreme temperatures break apart otherwise stable atmospheric nitrogen (N2) and oxygen (O2) molecules. As the superheated air cools, free atoms recombine into nitrogen oxides, including nitric oxide (NO) and nitrogen dioxide (NO2).

Collectively known as NOx, these compounds serve as the primary precursors for ozone formation.

Over the hours following a thunderstorm, sunlight drives photochemical reactions involving NOx that generate significant quantities of tropospheric ozone.

Direct Ozone Formation

Lightning can also create ozone directly.

The electrical discharge itself can split oxygen molecules into individual oxygen atoms. These atoms rapidly combine with nearby oxygen molecules to form ozone.

This process helps explain the characteristic sharp odor often associated with thunderstorms and demonstrates that lightning can generate ozone even in the absence of ultraviolet radiation.

In effect, lightning functions as a natural atmospheric plasma reactor, supplying sufficient thermal and electrical energy to drive ozone chemistry independently of solar ultraviolet radiation.

Tropospheric Ozone as a Greenhouse Gas

Once formed, ozone behaves identically regardless of whether its precursor gases originated from lightning, wildfire smoke, industrial emissions, or transportation sources.

Tropospheric ozone absorbs outgoing thermal infrared radiation emitted by Earth’s surface and lower atmosphere. This energy is then partially re-radiated back toward the surface, contributing to additional warming.

The altitude at which ozone forms is particularly important.

Lightning injects NOx directly into the middle and upper troposphere, where ozone can exert a disproportionately large radiative effect. Because these regions of the atmosphere are colder than the surface, ozone is especially effective at trapping outgoing infrared radiation.

Consequently, ozone produced by lightning often has a greater warming impact per molecule than ozone formed closer to the ground.

Tropospheric Ozone as a Biological Toxin

The climatic effects of ozone represent only part of its significance.

Tropospheric ozone is among the most damaging air pollutants affecting terrestrial vegetation.

When ozone enters plant leaves through stomata, it initiates oxidative reactions that damage cells and disrupt normal physiological processes.

Documented effects include:

• Reduced photosynthesis
• Oxidative stress
• Cellular membrane damage
• Impaired stomatal regulation
• Reduced carbon assimilation
• Lower growth rates
• Reduced crop yields
• Increased susceptibility to drought
• Increased vulnerability to pests and disease
• Increased tree mortality

Numerous studies have documented productivity reductions ranging from approximately 10 percent to more than 40 percent depending on species, environmental conditions, and exposure levels.

Ozone should therefore be viewed not merely as an air pollutant but as a large-scale ecological forcing agent.

Carbon Sink Degradation

The ecological consequences of ozone extend directly into the global carbon cycle.

Forests, wetlands, grasslands, and agricultural systems collectively remove vast quantities of carbon dioxide from the atmosphere through photosynthesis. This natural carbon uptake has historically slowed the rate of climate change.

When ozone suppresses photosynthesis, carbon uptake declines.

Reduced productivity means less carbon is transferred from the atmosphere into plant biomass and soils.

The result is a secondary warming mechanism:

Ozone Formation → Reduced Photosynthesis → Reduced Carbon Uptake → Increased Atmospheric Carbon Dioxide → Additional Warming

Unlike ozone’s direct greenhouse effect, this pathway operates through biological degradation of Earth’s natural carbon-removal systems.

Lightning, Ozone, and Ecosystem Vulnerability

Vegetation weakened by chronic ozone exposure becomes increasingly susceptible to other climate-related stressors.

These include:

• Heat waves
• Drought
• Water scarcity
• Insect outbreaks
• Pathogen attacks
• Wildfire exposure

As climate warming intensifies many of these pressures, ozone can act as a force multiplier that reduces ecosystem resilience precisely when resilience is most needed.

This interaction suggests that lightning-generated ozone may influence climate not only through atmospheric warming but also through ecosystem destabilization.

Wildfires and Ozone Amplification

Recent research has highlighted the growing importance of wildfire emissions in ozone formation.

Wildfires release substantial quantities of:

• Nitrogen oxides
• Carbon monoxide
• Volatile organic compounds
• Fine particulate matter

These emissions undergo photochemical reactions that generate ozone far downwind of the original fire source.

At the same time, ozone weakens vegetation and increases vulnerability to drought and fire.

This creates an additional reinforcing cycle:

Climate Warming → More Wildfires → More Ozone → Greater Vegetation Damage → Reduced Ecosystem Resilience → More Wildfires

The wildfire-ozone interaction links atmospheric chemistry directly to ecosystem degradation and carbon-cycle disruption.

The Temperature-Lightning-Ozone Feedback

Climate warming may increase lightning activity itself.

According to the Clausius-Clapeyron relationship, the atmosphere can hold approximately 7 percent more water vapor for every 1°C increase in temperature.

Additional moisture fuels stronger thunderstorms and increases Convective Available Potential Energy (CAPE), creating conditions favorable for lightning formation.

Multiple studies have suggested that lightning frequency could increase by roughly 10 to 12 percent for each degree Celsius of warming.

This relationship creates a potential reinforcing feedback:

Warming → More Atmospheric Moisture → More Thunderstorms → More Lightning → More Ozone → More Warming

Because ozone is both a greenhouse gas and a biological stressor, this feedback may operate through multiple pathways simultaneously.

The Expanded Earth-System Feedback Network

When vegetation and carbon-cycle effects are incorporated, the feedback structure becomes considerably more complex.

Global Warming

↓

More Atmospheric Moisture

↓

More Energetic Thunderstorms

↓

More Lightning

↓

More NOx Production

↓

More Tropospheric Ozone

↓

Direct Atmospheric Warming

Reduced Plant Productivity

↓

Reduced Carbon Sequestration

↓

Higher Atmospheric Carbon Dioxide

↓

Additional Warming

↓

More Lightning

At the same time:

More Ozone

↓

Weaker Vegetation

↓

Greater Drought Sensitivity

↓

Increased Wildfire Risk

↓

More Ozone Precursors

↓

Additional Ozone Formation

The result is an interconnected network of reinforcing feedbacks linking atmospheric physics, atmospheric chemistry, ecosystem productivity, wildfire dynamics, and climate change.

The Counterbalancing Role of Hydroxyl Radicals

Lightning does not exclusively produce warming influences.

The same electrical discharges that generate NOx also produce hydroxyl radicals (OH), often referred to as the “detergent of the atmosphere.”

Hydroxyl radicals react with methane, one of the most powerful greenhouse gases, accelerating its removal from the atmosphere.

This creates an important negative feedback:

Lightning → More OH Production → Increased Methane Destruction → Reduced Warming

The methane-removal pathway partially offsets warming caused by ozone formation.

However, when vegetation damage, carbon sink degradation, and wildfire amplification are included in the analysis, the overall balance may shift toward a stronger net warming influence than previously recognized.

Conclusion

Lightning is more than a spectacular atmospheric phenomenon. It is an important driver of atmospheric chemistry, ozone formation, ecosystem productivity, and climate dynamics.

By generating NOx and ozone in the upper troposphere, lightning contributes directly to greenhouse warming. By damaging vegetation and weakening carbon sinks, ozone contributes indirectly to additional warming through biological pathways. By increasing ecosystem vulnerability, ozone may also strengthen wildfire-driven feedbacks that further amplify climate change.

At the same time, lightning-generated hydroxyl radicals provide a partial counterbalance by accelerating methane removal.

Understanding the net effect of these competing processes requires moving beyond traditional atmospheric chemistry frameworks toward a fully integrated Earth-system perspective. Such an approach may reveal that lightning-generated ozone occupies a more significant role in climate feedback dynamics than previously appreciated.

Addendums

Why does ozone make the air smell “better” around lightning strikes? Are we breathing in ozone?

Yes, You Are Breathing It In

When you take a deep breath during a thunderstorm and notice that crisp scent, you are absolutely breathing in real ozone molecules (O₃).

The electricity from lightning splits standard oxygen (O₂) molecules into individual oxygen atoms, which quickly fuse with surrounding oxygen molecules to form ozone right at the storm front. Powerful wind downdrafts then push this newly minted gas straight down to ground level where your nose picks it up.

3. The Catch: It is Actually Toxic

Despite smelling clean and healthy, ozone is a highly toxic, destructive gas.

• The Chemistry: Ozone is an incredibly powerful oxidant. Because it has three oxygen atoms instead of the stable two, it is highly unstable and aggressively seeks out organic matter to react with.
• What it Does to Your Lungs: When you inhale it, ozone immediately attacks the cells lining your respiratory tract. It creates severe oxidative stress, inflames your airways, can constrict your chest, and can trigger asthma or coughing fits.

The Additional Wildfire > Lightning > Ozone Feedback

Wildfires, Lightning, and Brown Carbon

Hotter temperatures increase lightning, sparking more wildfires that release CO2 and brown carbon. Brown carbon settles on snow and ice, darkening surfaces and speeding up melt. According to Forests at Risk Due to Lightning Fires, 77% of forest fires in intact non-tropical regions are now lightning-caused. Lightning strikes are projected to increase by 11-33% per degree of warming.

“Thousands of lightning strikes in remote forests can spark hundreds of small fires. These merge into mega-fires–blazes the size of small countries. Once they reach this scale, they’re nearly impossible to stop.”
— Prof. Sander Veraverbeke

The Canadian wildfires of 2023 released more CO2 than nearly any country annually, and in some areas, permafrost is now burning year-round.

Studies have identified a feedback loop between lightning and forest fires. Global warming increases extreme weather events, conducive to lightning. More lightning ignites trees and soil, releasing warming CO2, creating more storms and lightning. The Forests at Risk Due to Lightning Fires study reveals the sensitivity of intact forests to potential increases in lightning fires, impacting terrestrial carbon storage and biodiversity.

“What many people may not be aware of is that lightning is the most common ignition source for fires in remote temperate and boreal forests,” says Thomas Janssen, research associate at VU Amsterdam. These forests store large amounts of carbon, which is released in the form of greenhouse gases during the fire. The research reveals that 77% of the burned area in intact forest regions outside the tropics is due to lightning fires, and the number of strikes is expected to increase by 11 to 3 % per degree warming with ongoing climate change.

“When a thunderstorm passes through this landscape, there are thousands of lightning strikes, and some hundreds of them start little fires,” said Prof Sander Veraverbeke from the Vrije Universiteit Amsterdam, one of the authors on the research paper. “And these can grow together into mega-fire complexes that become the size of small countries. Once these fires are so big, it becomes very difficult to do anything about them.”

More wildfires create more CO2 and more brown carbon that result in more global warming that results in more lightning strikes creating more wildfires resulting in more global warming thawing more permafrost allowing more emissions of CO2 and methane resulting in more warming, creating many more feedback loops. The Canadian wildfires of 2023 are a clear example of a tipping point that has been crossed. These fires released more carbon into the atmosphere than the annual emissions of all but three countries. Permafrost, once considered a stable, frozen barrier, is now thawing and burning year-round, releasing even more carbon and methane into the atmosphere.