Actually I can think of several positives behind a worsening eruption (if any)
Aerosols minimize AGW, resulting in a wash.
Military airstrikes and existing wars may have to be scaled down or called off.
Aviation drain of petrolium products reduces, resulting in a greater supply, less demand--and hopefully lower petrol prices.
Lastly, and perhaps more importantly, if volcanic activity increases, Jet travel will no longer have a foot on the throat of alternative means of transportation, resulting, I hope in renewed interest in the following:
1.) Bering Strait Bridge/Tunnel concepts.
London to Rio anyone?
2.)The S.S. United States being brought back into service.
(existing shallow water fun ships would roll in freak waves if pressed into service for trans-Atlantic trips).
3.)The return of large Airships. Engine nacelles can be serviced in flight, unlike any other aircraft. Air Filters replaced in transit with ease. Envelopes equipped with solar panels and/or other electric drives to allow nacelles to omit air-breathing entirely. Ion wind propulsion to keep dust at bay and allow forward travel. Modern weather forecasting allows steering around convection.
If hostilities increase along with ash, Space based weapons may replace air strikes.
Jet aviation's maturity into fighters and ho-hum twin jets for Delta has killed so much of the "Sky Captain and the World of Tomorrow" concepts we were all supposed to enjoy.
So I say..."Thank you for Smoking"--and keep it up.
http://www.foxnews.com/scitech/2010/04/19/iceland-volcano-ash-coming-america/
http://www.earthice.hi.is/page/ies_Eyjafjallajokull_eruption
http://en.wikipedia.org/wiki/Eyjafjallaj%C3%B6kull
Next at bat--Katla:
http://en.wikipedia.org/wiki/Katla