
I didn't learn about it until a day or so ago. It's been promoted on Facebook and by @ClimateTruth and others on Twitter, but so far I haven't found any blog or normal website or much of anything else.
The rally is at Jessie Square, 740 Mission Street, San Francisco, CA on Tuesday 13 December at 12 PM - 1:30 PM PST. (see map)
Despite the minimal publicity, lots of people will be there from what I can gather. The 25k plus crowd at AGU provides a decent base from which to draw people to rally. So if you're in the San Francisco area - go and show your support for science. If you can't make it, I understand the event will be streamed live from the Facebook page of ClimateTruth.