Perhaps I am being very skeptical, but I am failing to understand how three months of lockdown all the sudden eliminates decades of pollution. Something does not add uphere.
You've probably never been in a city that has bad pollution if you think this way.
Of course, 3 months of lockdown won't eliminate decades of pollution, but clearing the air and letting all the airborn suspended particles fall to the ground and pulling the dust out of the air makes it clear.
The other viewpoint is that you just don't realize how bad modern pollution is. In Toronto, ON, people are reporting being able to see Niagara Falls from a regular vantage point in the city after a few months of shutdown.
A huge amount of low-level airborne particulate comes from the wear between tires and the road and vehicular exhaust, and compounded with exhaust fumes from industry this creates much of the low-level airborne particulate.
The high-atmosphere pollution remains, as does the soil and water and biomass pollution, but the low-level airborne particulate is heavily influenced by automobile traffic and industrial activity.
Pollution is not permanent - it has a half-life in the air/water/ground. (Assuming exponential decay, which is a decent heuristic.) "Permanent" forms of pollution are just those which have unreasonably long half-lives, like some radioactive waste in the millions of years.
So CO2, which is of course a big deal now, isn't actually permanent, but its half-life is on the order of a couple of decades (the decay model is one of the big open problems in climate modeling) - hence the talk about how even if we stop emitting today, the problem will still be around. Whereas methane, a stronger greenhouse gas, has a half-life of only around 5-10 years.
Particulates have a much shorter half life before they settle to the ground; and, because they are a local form of pollution, they have a very short half-life before being blown away and diluted. If you've been following California news, this is why the massive pollution caused by recent forest fires went away within a few days of the fires dying out. If you're in any big and polluted city, this is why air quality can vary wildly from day to day with weather conditions and economic activity, leading weather forecasts to include an air quality forecast.
Imagine in your home city overcast clouds, dark skies. All of a sudden there's a downpour of a rainstorm. After a whole night of raining, the next morning, why does the sky appear blue and clear?
Is it that all of the clouds were destroyed and that they will never reappear again? No - it's because the clouds were carrying the mist and the water vapour, which "precipitated" out of the sky as liquid since the water droplets are heavier than air.
After it rains, the clouds disappear. The clouds didn't go away into nowhere. You can be skeptical about whether I'm writing about a magical statement, but you can observe yourself that after a period of intense rain -> the clouds go away and you can see the blue sky and clear across the city all of a sudden.
Will you be skeptical about this scenario as I described it?
Road vehicles and agricultural vehicles have both been using ULSD for the past 10 or so years in America, and it's my impression that this is common elsewhere in the developed world too. ULSD has two orders of magnitude less sulfur than common jet fuel.
Is there any reason jet aircraft couldn't burn something like ULSD? ULSD has a sulfur content of 15ppm in North America, whereas jet fuel can apparently be 2000ppm or more.
