When thinking of all the AGW pseudoscience swallowed by the GAC (Global Alarmist Church ... pronounced as G-A-C-K-K-K-K !!! with a gutteral ending as if you have a throat clogged with nasty phlegm and you are "hawking a loogie") you get an overwhelming involuntary reflex to spit on the nearest climatologist).
US southern slang. Usually preceded or followed by "now."
It means "listen to what I have to say next, because it is something that you were unware of or had previously been ignoring, much to our chagrin."
or can simply mean "look at this."
Now, lookie here: we don't appreciate that kind of foul language here.
Lookie here now: The way you're cutting them switches is all wrong. Use a sweeping motion.