This article is part of our 4-part mini-series exploring the hidden ripple effects of sulfur reduction in shipping. Read the next part → under investigation, available shortly!
In early 2020, the world did something that seemed unambiguously good: it slashed sulfur emissions from international shipping.
The International Maritime Organization (IMO) introduced new regulations requiring ships to drastically reduce the amount of sulfur allowed in their fuel. It was a public health victory—one that promised cleaner air, fewer respiratory illnesses, and less acid rain. That was the intention.
But then something strange happened.
Lightning… disappeared.
Not everywhere, of course—but satellite data revealed a surprising drop in lightning activity over major shipping routes, particularly in the Indian Ocean and South China Sea. Scientists were baffled. Had the cleaner fuel somehow silenced the skies?
The answer appears to be yes—and that raises some deeply unsettling questions.
A Chain Reaction No One Predicted
Before the 2020 rule change, large cargo ships burned heavy fuel oil rich in sulfur. These emissions released aerosol particles into the atmosphere—tiny specks that act as cloud condensation nuclei. These help water droplets form and cluster into clouds. More aerosols can mean more—but smaller—droplets, which influences cloud dynamics and increases the chances of storm development and lightning.
So when sulfur emissions dropped sharply, so did the number of aerosols. With fewer of these particles seeding clouds, lightning strikes over the oceans began to fade.
Some scientists warn that we may also be lifting a kind of atmospheric veil—known as “global dimming”—which has been quietly offsetting some of the effects of global warming. Removing sulfur doesn’t just clean the air; it may also reveal what’s been hiding underneath.
This wasn’t just a tweak. It was a system-wide nudge, and it rippled outward in ways we didn’t expect.
Good Intentions, Complex Systems
Environmental policy often focuses on direct, measurable outcomes: reduce sulfur, reduce pollution-related deaths. And that’s not insignificant. But Earth’s climate and weather are interconnected systems, not simple input-output machines.
When we remove one part of a system—like sulfur aerosols—we don’t just remove a pollutant. We remove something that was playing a quiet role in temperature regulation, cloud formation, and yes, lightning.
This is the essence of the law of unintended consequences: well-meaning interventions that set off a domino effect we didn’t foresee. It’s not that cutting sulfur was a mistake—but it’s a powerful reminder that even our clean-up efforts come with trade-offs.
What Else Are We Not Seeing?
If removing sulfur can reduce lightning, what other atmospheric roles have these “pollutants” been playing? Could we be unmasking deeper issues—like the true extent of global warming—by scrubbing the sky clean?
This isn’t about fearmongering. It’s about asking better questions.
- What else changes when we push for a cleaner world?
- Are our “green” policies sometimes too narrow in scope?
- And how often do we wait until after the fact to find out?
These are the kinds of ripple effects we aim to explore—not to cast doubt, but to expand the conversation and ask better questions.
A Bigger Pattern?
This isn’t the first time we’ve tried to fix a problem and created new ones:
- The pesticide DDT was hailed as a savior—until it devastated ecosystems.
- Biofuels promised clean energy—then drove up food prices and land use.
- Plastic bans helped with waste—only to boost demand for paper and aluminum, which have their own environmental costs.
Of course, not all fixes backfire. Some—like phasing out leaded gasoline—have produced major net benefits. But the ones that don’t go as planned are worth studying closely.
Sulfur’s role in lightning is just the latest chapter in an ongoing story: the story of how every solution lives within a web of other consequences.
Coming Up Next:
In Part 2, we zoom out and ask the bigger question:
“When Cleaner Isn’t Simpler: Why Fixing One Problem Might Create Another”
Because maybe it’s not about cleaning things up more—but understanding them more deeply first.
Further Reading: The Law of Unintended Consequences
International Maritime Organization – “IMO 2020 – Cutting Sulphur Oxide Emissions”
🌍 Global regulations to reduce sulfur emissions from ships
URL: https://www.imo.org/en/MediaCentre/PressBriefings/pages/34-IMO-2020-sulphur-limit-.aspx
This IMO press briefing details the implementation of the 2020 global sulfur cap, aimed at reducing sulfur oxide emissions from ships to improve air quality and protect the environment.
Lightning Declines Over Shipping Lanes Following Regulation of Fuel Sulfur Emissions
⚡ Investigating the link between sulfur regulations and lightning activity
URL: https://acp.copernicus.org/articles/25/2937/2025/
This study examines how the 2020 global sulfur cap on ship fuels led to a noticeable decrease in lightning over major shipping routes, highlighting the complex interactions between human activities and atmospheric phenomena.
NASA Earth Observatory – “Ship Tracks”
🧭 How ship emissions affect cloud formation and weather
URL: https://earthobservatory.nasa.gov/features/ShipTracks
This NASA explainer dives into the phenomenon of “ship tracks”—long clouds formed by the particles in ship exhaust—and their effect on sunlight reflection and cloud behavior.
Sulfur Cycle – an overview | ScienceDirect Topics
🌎 The sulfur cycle in aquatic systems is indirectly important to ecosystem productivity
URL: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sulfur-cycle
This resource provides an in-depth look at the sulfur cycle, including the effects of human activities such as the production of acid rain.
Climate of Our Future – “Sulfur Dioxide Effects on Environment”
🌿 The environmental toll of SO₂ emissions
URL: https://www.climateofourfuture.org/sulfur-dioxide-effects-on-environment/
This article explores three major environmental impacts of sulfur dioxide—plant damage, acid rain, and haze—highlighting the need for cleaner energy sources and stricter emission controls.
Books:
The following book is linked to Amazon.com for your convenience. If you decide to purchase through this link, we may earn a small commission — at no extra cost to you.
Fundamentals of Geobiology [amazon.com]
Editors: Andrew H. Knoll, Don E. Canfield, Kurt O. Konhauser
Description: This work examines the interactions between the biosphere and the geosphere, discussing cycles such as the sulfur cycle and their role in Earth’s history.
This is Part 1 of a 4-part series on the surprising environmental effects of sulfur regulation and what it reveals about our approach to climate solutions.
In this series:
- ✅ The Law of Unintended Consequences – You are Here!
- ✅ When Cleaner Isn’t Simpler
- ✅ What If Our Environmental Fixes Backfire?
- ✅ We Meant Well—But Did We Forget to Ask the Right Questions?
🔎 Bonus: From Lead to BTEX – Did We Trade One Toxin for Another?
Image Acknowledgement
We’re grateful to the talented photographers and designers on Unsplash for providing beautiful, free-to-use images. The image on this page is by Olga Gryb. Check out their work here: https://unsplash.com/@grybdesigns/illustrations.
