Extinction

[Rik Hill <rhill@LPL.Arizona.EDU>]

> I was always under the impression that the unpleasent climatological effects
> of the meteor (or volcanoes, or what have you) continued for a long time,
> several years or decades. 

Let me point out that we don't KNOW that yet. Your time bracket,
"several years" to "decades" is an indication of the large error bars
on such predictions. The current thinking on suspension of particulates
in the atmosphere is based largely on volcanic eruption ejection of
such into the atmosphere. It may be that an impact is nothing like a
volcanic eruption. For years now there has been a Sagan-esque
equivalence between volcanic eruption effects, nuclear winters and
impacts but in truth, without an impact on a terrestrial planet that we
can study we can only extrapolate.  Studying craters is helpful but
it's like describing a whole new dinosaur on the basis of one bone,
there's a lot of extrapolation.

To give you an idea of the situation, take the latest Science News.
There's an article on how dust in the atmosphere causes a paucity 
of precipitation. For years we were led to believe that dust was
a site for condensation and later precipitation. Just this one study
alone would have a profound effect on impact effect studies in 
understanding how long water vapor clouds would blanket the earth, 
how long dust would be suspended in the lower atmosphere, what would
be the reflectivity of the atmosphere (since dust and water vapor
have very different albedos). 

-Rik