Climbing a building that turned to ice

I'm halfway up what I thought was a frozen waterfall, but when I look down it's the side of a concrete parking garage, and there's a man in a sedan watching me through his windshield. The ice creaks like it's breathing, and I can smell exhaust and condensing breath—cold and metallic. Then I realize I'm not wearing a harness, but I can't fall, because falling would mean waking up.