Here's a good article at Forbes regarding independent verification of global warming via a number of proxies that tends to corroborate the coincidence of warming with industrialization.
There's a nice video that goes with it regarding the research.
I'm not sure when we hit a point of data saturation at which denialists actually throw up their hands and say "I'm out!" but every little bit helps. This study is kind of a good news/bad news thing. Good news: it corroborates that the science is simply not shitting about global warming being man-made and totally happening; bad news: global warming is actually totally happening.