This is perhaps the most thoroughly researched finding in the history of science. Because there was a systematic effort to undermine the science, huge percentages of people do not realize how gigantic the research is, how broad is the range of sciences involved (physics, biology, chemistry, geology, you name it) and how PROFOUNDLY aligned all the research is.
We have tens of thousands of researchers from all over the world, in a host of scientific disciplines, looking at everything from CO2 content in the atmosphere to tree rings to ice cores, and there is an astonishing convergence in the conclusion:
1. The Earth is warming far more than normal and natural cycles would predict
2. The primary cause of this warming is an increase in greenhouse gases due to human activity.