What would be undeniable proof of man-made global warming?

It's impossible to prove global warming is anthropogenic (man made). Many of the worlds leading scientists are now jumping off the man made global warming theory bandwagon. While CO2 is a greenhouse gas it is too small a player to contribute to accelerated warming. Water vapor is the big player in greenhouse gas. CO2 levels in the atmosphere were higher leading into the last ice age then they are predicted to be in the next 100 years. Most people assume CO2 is a man made toxic gas. The truth is it it the foundation of all life on earth. When CO2 levels are elevated the worlds vegetation grows at an accelerated rate. The oceans scrub up to 50% of the CO2 from the atmosphere. The problem with the science that claims during the warmest periods on earth CO2 was elevated is that a warmer earth PRODUCES more CO2. The science that global warming is man made is very dubious. That being said, we should still continue to develop alternative clean sources of energy.