Well,
IMO
Nuclear Winter: We will hopefully never know if the scientists were right - although we may now be able to model what would have happened if 100,000 nuclear warheads had been set off in the space of 6 hours C.1970, and see if some of us would still be around or not. Its very possible we wouldn't.
SETI: The equation is legitimate and scientific - it sets out a series of variables that can be narrowed down over time. Its possible there is something out there somewhere.
One thing's for sure though - the politicians only ever listen to scientists when it suits them. They don't like to face facts when the news is bad.
There's a huge amount to do at the moment, and politicians are just holding up progress. Chrichtons article IMO is depressingly negative, but I would be suprised if he still holds the same opinions now after the last year - he's not stupid.
Dave L