From your link -
Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities,and most of the leading scientific organizations worldwide have issued public statements endorsing this position.
They don't KNOW.
By the same standards it must follow that any who say that humans aren't responsible can't KNOW either.
To be honest any scientist ( or anyone for that matter) who says they are 100% certain either way would concern me. As I said earlier any complete scientific testing would require a second planet as a control.
Personally I find it hard to believe that we could pump a trillion tonnes of carbon into the atmosphere and expect there to be no effect. It would be arrogant to think otherwise.
However, having said that I also find it hard to believe that natural cycles don't play a part. That would be equally arrogant to think we had completely dominated nature.
The truth , I tend to believe, lies somewhere between the two camps. Natural warming and cooling occurs but our efforts aren't helping and may very well be making it worse.
Either way be it natural or man made climate change will affect us. How many of our cities are built next to the sea and will be prone to flooding? Most of our civilisation and agriculture is based around " normal " weather patterns. The human species will most likely ( 97% certainly ) survive but wether seven billion of us could survive may very well be less likely.