What are the levels of sulphur/sulfur emissions (1991-2001)-
Global/Developed/Developing World/Individual countries?

See

"This paper provides global and country by country estimates of sulfur
emissions for the early and mid-1990s. Raw estimates are obtained in
two ways. For countries with published data we compile that data from
the available sources. For the remaining countries, we use either the
decomposition model estimated by Stern (1999), the first differences
environmental Kuznets curve model estimated by Stern and Common
(2001), or simple extrapolation depending on the availability of data
on the explanatory variables. We then examine the compatibility of
these estimates with the ASL estimates for 1990. Based on these and
other comparisons we construct a preferred database for 1850-1999 and
discuss the main movements in the 1990s. The data is available from
the datasite. "

http://cres.anu.edu.au/~dstern/EEP/0103.html

http://cres.anu.edu.au/~dstern/EEP/eep0103.pdf

LR

See also

http://weather.engin.umich.edu/geia/emits/so2.html

Which has global SO2 emmissions,

I don't think you'll be able to find complete data beyond 1999.

Here is the search strategy I used

global sulfur emissions 2000 (I also tried various other dates without
additional success)

LetterRip