The world is set for a "big chill," possibly a mini-ice age, according to the venerable and whimsical Old Farmer's Almanac, first published in 1792 and the United States' oldest continuously published periodical.  The 2009 edition, published earlier this month, predicts that the earth already has entered a sustained period of global cooling.  True to form, the almanac also includes tips on gardening and how to stay warm all winter with just one log.  "The next 20 years, it's going to be colder," said Sarah Perreault, assistant editor of the Old Farmer's Almanac. "We do recognize that (global cooling) could be offset by greenhouse gasses and other human effects on the earth, but we're trending toward the cool period now."  Full Story