By itself, climate change does not threaten human extinction. That is, we are not going to fry to death on a 200 degree earth. However, the side effects are likely to. I'm sure you're aware of that people like Frank Fenning, James Hansen, and James Lovelock, reputable and knowledgeable scientists, do discuss openly the likelihood of a massive human extinction event within the lifetimes of people alive today.
http://www.physorg.com/news196489543.html
The problem is that there is so much inertia in the systems, both political and atmospheric, that quite drastic decisions made today can only lessen the horrors of 2100.
http://www.realclimate.org/index.php/archives/2010/06/climate-change-commitment-ii/
There is an interesting point here about risk management: Is it better to tell the whole truth, and risk panic, or is it better to tread a careful line and hope to convince people to do what is needed, even after the point of no return has been reached?
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To convince a person, you have to meet them where he or she is, not where you are. So unless you are in the privileged position to talk to humanity all at once, I do not think that really is choice. A vote for PES is a vote for EPP! A vote for EPP is a vote for PES! Support the coalition, vote EPP-PES in 2009!
