Science Snippets: Lightning Terminated Via Regulation of Fuel

Draft script:

I have spoken frequently in this space about the aerosol masking effect. This video provides a short summary and an update. The latter is based on an article at The Conversation written by a postdoctoral research fellow at the University of Washington.

First, the short summary of the aerosol masking effect. Just as industrial activity produces greenhouse gases that trap heat, industrial activity also produces small particles that reflect back into space some of the incoming sunlight. These tiny particles are called aerosols, and they reflect incoming sunlight before this incoming radiation can be used to heat Earth. As I have mentioned frequently in this space, Professor James E. Hansen has pointed out in many interviews and peer-reviewed papers that the aerosols produced by industrial activity fall out of the atmosphere in about five days. If industrial activity were to suddenly stop, then the planet would heat very rapidly. Hansen calls this our Faustian bargain. I have referred to it as the best-kept secret in climate science because it is seldom mentioned by political figures, media personalities, or paid climate scientists.

A peer-reviewed, open-access paper published in Geophysical Research Letters on 10 July 2019 indicates that the loss of aerosol masking would produce an enormous impact, based only on reduced albedo, or reflectance. Not including factors such as increased methane being released into the atmosphere, the Abstract of the paper points out that “this is equivalent to the effect of one trillion tons of CO₂ emissions.” This “would hasten global warming by an estimated 25 years.”

A peer-reviewed, open-access paper published 15 June 2021 in Nature Communications indicates that loss of aerosol masking would lead to much higher radiative forcing than indicated by previous research. Specifically, radiative forcing would increase 55% globally. Worse yet, radiative forcing would increase by 133% over land, where most of us live.

According to governments of the world, we have already eclipsed the 2 C Rubicon. Adding an additional 133% to the existing level of radiative forcing would take Earth quickly to 4.67 C. As I have mentioned several times in this space, the rapid rate of environmental change from about 2 C to more than 4.5 C above the 1750 baseline would be catastrophic for life on Earth. I doubt any species could keep with such a rapid rate of environmental change, and human animals are especially poorly suited for such a rapid change to the place we call home.

I turn now to the update, written by a postdoctoral research fellow at the University of Washington. Titled The world regulated sulfur in ship fuels − and the lightning stopped, this article was published on 11 March 2025. If you are familiar with the aerosol masking effect, the first three paragraphs tell the story: “If you look at a map of lightning near the Port of Singapore, you’ll notice an odd streak of intense lightning activity right over the busiest shipping lane in the world. As it turns out, the lightning really is responding to the ships, or rather the tiny particles they emit.

Using data from a global lightning detection network, my colleagues and I have been studying how exhaust plumes from ships are associated with an increase in the frequency of lightning.

For decades, ship emissions steadily rose as increasing global trade drove higher ship traffic. Then, in 2020, new international regulations cut ships’ sulfur emissions by 77%. Our newly published research shows how lightning over shipping lanes dropped by half almost overnight after the regulations went into effect.”

The second paragraph includes an embedded link to a peer-reviewed, open-access paper published in Geophysical Research Letters on 7 September 2017. Written by four scholars, this paper is titled Lightning enhancement over major oceanic shipping lanes. The first two sentences of the Abstract provide a good overview: “Using 12 years of high-resolution global lightning stroke data from the World Wide Lightning Location Network …, we show that lightning density is enhanced by up to a factor of 2 directly over shipping lanes in the northeastern Indian Ocean and the South China Sea as compared to adjacent areas with similar climatological characteristics. The lightning enhancement is most prominent during the convectively active season, November–April for the Indian Ocean and April–December in the South China Sea, and has been detectable from at least 2005 to the present.”

The Abstract is followed by three Key Points:

1. “Lightning is enhanced by about a factor of 2 directly over two of the busiest shipping lanes in the Indian Ocean and South China Sea”

2. “Environmental factors such as convergence, sea surface temperature, or atmospheric stability do not explain the enhancement”

3. “We hypothesize that ship exhaust particles change storm cloud microphysics, causing enhanced condensate in the mixed-phase region and lightning”

A Plain Language Summary reiterates the information found in the Abstract and Key Points. Here’s the lede: “Lightning results from strong storms lifting cloud drops up to high altitudes where freezing occurs and collisions between drops, graupel, and ice crystals lead to electrification.” I include the lede not because it provides significant additional information, but because it mentions my favorite form of precipitation: graupel. According to the Merriam-Webster Online Dictionary, graupel is “granular snow pellets.” It is also called soft hail.

As I indicated at the beginning of this video, the update I’m providing here is based on an article at The Conversation written by a postdoctoral research fellow at the University of Washington. Under a section titled Ship emissions and lightning, we find two important paragraph: “With engines that are often three stories tall and burn viscous fuel oil, ships traveling into and out of ports emit copious quantities of soot and sulfur particles. The shipping lanes near the Port of Singapore are the most highly trafficked in the world – roughly 20% of the world’s bunkering oil, used by ships, is purchased there.

In order to limit toxicity to people near ports, the International Maritime Organization – a United Nations agency that oversees shipping rules and security – began regulating sulfur emissions in 2020. At the Port of Singapore, the sales of high-sulfur fuel plummeted, from nearly 100% of ship fuel before the regulation to 25% after, replaced by low-sulfur fuels.”

Five paragraphs later, we find a review of this research: “In our latest study, my colleagues and I describe how lightning over the shipping lane fell by about 50% after 2020. There were no other factors, such as El Niño influences or changes in thunderstorm frequency, that could explain the sudden drop in lightning activity. We concluded that the lightning activity had fallen because of the regulation.

The reduction of sulfur in ship fuels meant fewer seeds for water droplet condensation and, as a result, fewer charging collisions between ice crystals. Ultimately, there have been fewer storms that are sufficiently electrified to produce a lightning stroke.”

The aerosol masking effect is well-described by this article in The Conversation. It reiterates the negative effects that result from well-intentioned regulations. It leaves us with a conundrum. Obviously, clean air is important. Equally obviously, if you’re paying attention, clean air has unintended negative impacts. Although we need clean air for our continued survival, we also need rainwater.

This recent research manages to differentiate between lightning and rain. It points out that fewer particles in the atmosphere results in fewer lightning strikes. This result is beneficial to everyone except wildland firefighters seeking more overtime pay. Lightning might be an indicator of more aerosols in the atmosphere, although confirmation will require additional research. In any event, the ability to distinguish between lightning and rain is a significant outcome and an indicator that we occupy a complex world.