1. That just shows that the global worming was taking place before humans had any kind of effect on nature
2. Because today many institutes and industries make a living out of "eco rubbish" (for example hybrid or electric car)
3. It's not about additional emissions, it's about how little humans activity adds to the global amount of Carbon-di-Oxide
1. You're talking about completely different time scales here. The climate might vary on very large time scales and indeed have been warmer at some points in the distant past; but the recent warming we are seeing is taking place far faster, in the order of decades.
2. And because of that, the overwhelming majority of scientists from all over the world completely ignore a potentially revolutionary discovery? That's not how it works. Besides, far more powerful and influential industries have a vested interest in making people believe climate change is not real, and they've only been able to buy a handful of scientists.
3. It is about additional emissions: if you have a balancing scale with 50kg on each side and proceed to add 1kg to one side, the plates will shift. Same thing here.