"Global warming kills more people than 9/11 every week."
Apart from the grammatical issues in it, including what I believe is a misplaced modifier*, that sentence troubles me. Protesting climate change is much different than protesting man-made climate change:
"Sacre merde, World! Will you stop getting warmer, and then cooler, and then warmer, and then cooler?? It seems like we go through this every year, no?"
Claiming that "global warming" kills people is like saying that time is the leading cause of death. If we could only stop it, everyone could live forever! But seriously, I can understand his wanting to bring attention to man's impact on the environment because that's the one issue that I haven't really seen much about in the news.
*First of all, 9/11 didn't actually kill anyone. It's just a day...and I guess technically, it should be 9/11/01. I think it would read better as "Every week, global warming kills more people than were killed on 9/11" or "Global warming kills more people every week than were killed on 9/11." It may seem like I'm nit-picking, or being hard on a non-native speaker, but c'mon--if you're going to risk your life to make a statement, I would think you might ask around and make sure what could be your final words are grammatically correct.
UPDATE: Apparently, there was a copycat climber. The new guy was climbing with a shirt that read "malaria no more." What's next? Erectile dysfunction? I can see the banner now: "I'm gonna get up it so you can get it up!"