The reason why there's a 97% consensus is because of the many lines of evidence that humans are causing global warming. Human fingerprints are being observed in heat escaping out to space, in the structure of the atmosphere and even in the changing seasons. Another denialist technique used to counter the weight of evidence is the logical fallacy.
The most common fallacious argument is that current climate change must be natural because climate has changed naturally in the past. This myth commits the logical fallacy of jumping to conclusions. It's like finding a dead body with a knife sticking out of its back, and arguing that the person must have died of natural causes because humans have died of natural causes in the past. The premise does not lead to the conclusion.