The hypothesis for climate change has been easy to prove. That's because the evidence for climate change is ubiquitous and (increasingly) undeniable.
Thus, the (climate change) deniers have transformed their contentions from "Climate change is not occurring" to "Ok...climate change is occurring, but it's not due to human activity."
Proving climate change is (at least) exacerbated by human activity is relatively difficult. But, making a logical case for adopting that hypothesis is not:
1. We know we are injecting large amounts of carbon dioxide into our atmosphere that otherwise would remain locked in hydrocarbons. We know carbon dioxide absorbs infra-red radiation that would, otherwise, be re-radiated into space and, therefore, CO2 traps heat in our biosphere.
2. We know, from experience and thoughtfulness, it is best to take the safe course when doubt exists. So, we should assume CO2 is a global-warming perpetrator until proven otherwise.
The onus should be on anthropogenic global warming DENIERS to prove their case rather than vice versa. That is common sense.