This article claims there're 2X lightening strikes over shipping lanes, because of additional particulates in the upper atmosphere.
How do we reconcile this?
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.
What are you referring to by "settle out" and maps?
The map patterns are persistent because shipping traffic is constant, and there are a huge number of ships (~80,000 large cargo vessels worldwide), largely concentrated on narrow sea lanes. You can observe SO2 emissions along sea lanes using the Nullschool Earth Weather Visualiser: https://earth.nullschool.net
With "Chem" and "SO2sm" selected over the Indian Ocean, showing sea lanes between the Gulf of Aden and Straight of Malacca, discussed in the Wired article: https://earth.nullschool.net/#current/chem/surface/level/ove...
There are 100,000 vessels passing through the Strait of Malacca every year, that's over 270 per day.
As for other pollutants.
Elevated atmospheric CO2 due to industrial fossil fuel combustion is thought to extend for centuries to millennia.
The residence time of PM2.5 is on the order of 2-5 days. See:
10.1016/0048-9697(84)90285-7
Journal: Science of The Total Environment Volume: 36 Issues: none 339--346
Title: Atmospheric residence time of carbonaceous particles and particulate pah compounds
Author(s): Jürgen Müller
Publisher: Elsevier Science
Year: 1984"As a somewhat saving grace, these pollutants do tend to settle out quickly, and hence don't reside long in the atmosphere. "
Particulates are blamed for the lightning. If true, they must be present in significant amounts, at high altitudes?
Sorry for the typo; didn't mean to push your buttons.
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.
Trouble is there are no few week breaks in the schedule that ever let it actually settle out.