"If we were transported forward in time, to an Earth ravaged by catastrophic climate change, we might see long, delicate strands of fire hose stretching into the sky, like spaghetti, attached to zeppelins hovering 65,000 feet in the air. Factories on the ground would pump 10 kilos of sulfur dioxide up through those hoses every second."

A 100' of fire hose weighs about 50 lb. 65,000' of fire hose
would weigh about 32,000 lb. It would take a large zeppelin to handle the weight of 3 fire hose [96,000 lb] and to maintain a height of 65,000'.
The density of sulfur dioxide gas is 2.551 g/L.
Air is about 1.3 g/L, so it's roughly twice the density of
air. Suppose you wanted to pump air so it had 200 psi at a height of 65000'. How much pressure would you need at the bottom?

If you had a column of air 480' and you compressed it to 240' it would be twice the pressure and twice the density- plus it would generate heat- but we ignore the heat aspect as the moment. So, if it's at 14.7 psi it becomes 29.4 psi.
Compressed it to 120' it's 58.8 psi. Compress to 60' it's 117.6 psi. 30' it's 235.2 psi.
Now, suppose you pressuzed air at 235.2 psi at the bottom, would get around 200 psi at the top [65000' higher]?

Air normally at sea level is 14.7 psi and at 65000', air is normally less than 1/10th of sea level pressure- wiki:
52,926' equals 1/10th of 1 atm.
So without getting complicated, the 232.2 psi will be less than 1/10th of the 232.2 psi at 65,000'.
But it's actually much less than 23.2 psi at the top, because the compressed air has more mass/density, and since sulfur dioxide about twice air, it gets really grim.

Now suppose you doing something even harder, suppose you were trying pump water up 65000'. It's an atm every 33', so it requires 28,954 psi + 200 psi if you want to pump water to that height and have 200 psi at the top.
Btw nobody pumps water at this kind pressure- it breaks things. But if you want to pump SO2 as a liquid it's got a density of 1.46 g/cm3 (liquid)- more dense than water.

So, to keep it simple, you aren't going to be able to pump SO2 through fire hoses to 65,000'.

But let's say I am wrong. And you can pump 10 kg times 3 per second. There are about 30 million seconds in a year, so a Zeppelins does 900 million kgs per year- or .9 million tonnes per year.

"China is the world's biggest emitter of sulphur dioxide. Coal- and oil-fired power stations were responsible for 11 million of the 25 million tonnes discharged last year, which caused acid rain that affected a third of the country."

"Under the proposal, part of a drive to cut sulphur dioxide emissions by 10 percent by 2010, power stations would pay 630 yuan a tonne for the quotas, the Hong Kong paper quoted an environmental adviser to the central government as saying."
http://www.minesandcommunities.org/article.php?a=6360

"The 1991 eruption of Mt Pinatubo in the Philippines was one of the largest in the past 100 years. The injection into the stratosphere of 14-26 million tonnes of sulfur dioxide led to a global surface cooling of 0.5°C a year after the eruption. The climatic impact of the Pinatubo aerosol was stronger than the warming effects of either El Niño or human-induced greenhouse gas changes during 1991-93."
http://www.gaspig.com/volcano.htm

So, if China reduces it emission significantly at some cost in billions of dollars. We would need at least 20 of the these Zeppelins.

"And we could do it cheaply: $100 billion could reverse anthropogenic climate change entirely, and some experts suspect that a hundredth of that sum could suffice."

You would need 20 Zeppelins to match China emissions.
And another 20 to match Mt Pinatubo SO2 emissions.
You might be able to do this for 100 billion dollars- assuming you didn't count the yearly operational cost. Which btw is more than 5 times NASA's yearly budget.

And how are these SO2 emission better than SO2 emission the US electrical consumer spent tens of billions of dollars to significantly reduce?
I would say as a general approach, a large smoke stack with hot gases would probably do much better job at getting gases to altitude than trying force gas into fire hoses held up with enormous Zeppelins.