Lightning Strikes Twice as Much over Shipping Lanes

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That assertion seems ridiculous on the face of it. Even if the particles settle you're still polluting the ocean. Besides aren't gasses the main pollution problem anyways?

People confuse me sometimes...

To the extent that's mostly over the ocean, that could be consistent with claims that shipping particulate pollution has a minimal effect on the health of land-based humans.

Could you provide a citation?

If we reversed it, it would not be a measurable difference to over-sea pollution, but it would drastically increase over-land pollution.

In general, you have the following emissions from any fossil-fuel combustion process:

- Water vapour. This is virtually never harmful.

- CO2. This is not immediately toxic, but is a greenhouse gas, and net emissions must be reduced globally.

- Other combustion chemical products. Generally small fractions total emissions, though potentially hazardous to humans, including NOx (nitrous oxides), SO2 (sulfur dioxide), O3 (ozone), and trace pollutants such as mercury. All are bioactive or biotoxic.

- Physical emissions. In particular, fine particulate matter, essentially soot, most especially PM2.5 (2.5 micron particles). These are physical irritants and can contribute to lung injury and disease, among other factors.

Stating "ships emit X amount of pollutants" without specifying the pollutants is worse than useless, and often deliberately misleading.

Total CO2 emissions are wholly a function of the amount of fuel burned. Shipping is about 3% of total fossil fuel consumption, and hence, of total CO2 emissions. On net, and especially based on the total tonnage and value of goods moved, shipping is the most efficient form of transportation available. It is low polluting in terms of CO2.

Where ships trail, badly, is in particulate and chemical emissions. Ship fuel is "bunker oil", basically the last grade of petroleum above asphalt, and having a consistency when cold of tar or even a solid. Worse, it's also typically high in impurities, including sulfur, mercury, and other elements and chemicals. And when burnt tends to product high amounts of particulates. Given the regulatory environment, multinational, international waters, diverse, and often a race-to-the-bottom of bare minimum standards, marine emissions of these pollutants is high.

As a somewhat saving grace, these pollutants do tend to settle out quickly, and hence don't reside long in the atmosphere. Some, especially mercury, do reside in (and worse, bioaccumulate and concentrate) in life, which is why eating carnivorous fish (tuna, shark, swordfish) is not recommended.

But the full picture on shipping is that its pollutant levels vary greatly, compared to other sources, and in environmental impacts depending on the specific pollutants in question.

However, convective invigoration by aerosols is a different issue. They are suggestions that suppressing warm rain (rain formed through processes that don't involving ice) might lead to more intense updraughts in convective systems [2], but the observational evidence is unclear. Convective storms tend to form in humid locations, where satellite observations of aerosol are biased high by the humidity [3].

Even in this case, it is not clear that the result holds outside the local aerosol enhancement generated by ships [4]. Do aerosols affect convective clouds at a large scale? I would argue that there is no strong evidence either way at the moment.

[1] - https://en.wikipedia.org/wiki/Ship_tracks

[2] - http://doi.org/10.1126/science.1160606

[3] - http://doi.org/10.1002/2014GL059524

[4] - http://doi.org/10.1029/2018GL078682

Note that apparently the most common sulphur amount in fuel is around 2.7% (https://www.exxonmobil.com/en/marine/technicalresource/news-...). Currently there's not too much available fuel at 0.50%. What I heard is planned is that they're going to mix the 2.7% and 0.1% sulphur fuel to get to 0.5%.

Going from 2.7% to 0.5% sulphur fuel is apparently an additional cost of 15 billion USD/year. In my opinion once they're at 0.5% new legislation (by the IMO; an organization which basically sets these rules) should be introduced that reduces it further. Often in shipping the actual implementation date is 3-5 years, sometimes 10 years into the future. So new legislation should be introduced to reduce things further.

Secondly, companies can get a significant competitive advantage by not following these rules. As such, countries should be strictly checking if ships and shipping lines are following this. Unlike other industries it's pretty common that a captain is jailed if certain rules aren't followed.