A while ago I wrote briefly on why the Singularity might not be near and my estimates badly off. I saw it linked the other day, and realized that pessimism seemed to be trendy lately, which meant I ought to work on why one might be optimistic instead: http://www.gwern.net/Mistakes#counter-point
(Summary: long-sought AI goals have been recently achieved, global economic growth & political stability continues, and some resource crunches have turned into surpluses - all contrary to long-standing pessimistic forecasts.)
How does it substantially impact that probability?
One of the ways we can kill ourselves is global warming. Replacing coal power with solar power will reduce one of the causes of global warming -- namely, the greenhouse gases emitted from coal plants.