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Comment by CWuestefeld | Hacker News Reader

Compared to the 1970s and earlier, internal combustion engines are strikingly efficient. You're probably right that we've harvested all the low-hanging fruit, and further progress will be slow and slight.

But there's still a LOT of room for efficiency improvement by changing the other side of the equation. If we're generating power with nearly as much efficiency as possible, we can still go a long way in USING that power smarter.

Which is my long-winded way of saying that if everyone switched from driving big-ass SUVs to driving light compact cars, we'd still achieve a huge boost in miles traveled per pollutant emitted.

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You want low-hanging fruit, consider container ships. Can be up to 1/3 of global air pollution, from about 6000 vehicles. Because they use the dirtiest sulfer-laden diesel etc. They would be the biggest bang for the buck:

Wikipedia: "Of total global air emissions, shipping accounts for 18 to 30 percent of the nitrogen oxide and 9 percent of the sulphur oxides"

sails!

The problem is that it is politically impossible to implement the only solution that would take them to zero emissions. It is a solution that uses existing, proven, decades-old technology, but thanks to extremely powerful anti-science lobby groups we can't use it. Think about that for a minute: just how powerful does a lobby group have to be to prevent us implementing a solution to 1/3 of global air polution?

Everyone reading this, if they think for a few minutes, will be able to figure out what the technology is (because it's marine propulsion, and how do we make that zero-emission?) and who the political groups are who oppose it, so I'm not going to actually specify them because I think the point will have more impact if people work it out for themselves. The sad thing is that half of the people who do figure it out will have an immediate reaction of, "Well of course we can't do that!", thereby dismissing a practical, safe solution to 1/3 of global air pollution based on the nothing but politics, because what does the well-being of the planet matter when implementing a workable solution means changing your political stance on anything? That's something only those looney pro-science people do, right?

Those are short lived pollutants that do harm only if emitted in populated areas.

Yes, they are very dangerous in the middle of a city, and that's why urban vehicles almost don't emit them, making ships more representative.

Wha? They enter the atmosphere and circulate around the globe for years. Just because you don't see the grey clouds blowing in off the ocean, doesn't mean there's no problem.

Data is hard to find!

The best I could find gives nitrogen-dioxyde a half life of about 30 hours at the atmosphere, and sulfur-dioxyde about 5 hours.

I'd expect it to vary widely with local humidity (something the oceans have a lot), and I'd also expect the corresponding acids to fall down at the first rain (another thing the oceans have a lot), although the acids are already reasonably non-toxic.

Also, I'd expect those gases to not disperse in upper atmosphere, because of their molecular weight. But it thrown with any speed (like in a volcano eruption), they'd have the very low humidity, very low pressure that increases their life to a maximum.

Anyway, all that expectation is from theory. References are hard to find.

Confused; then why do we object to cars emitting these gasses?

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