The job of president is a job in which you make large decisions on subjects where you are not an expert.
It requires intellectual rigor. It requires the ability to assess what experts in a field are saying. To decide what the essential facts are from those experts.
If, in the face of an overwhelming consensus from experts in the field, you decide that a tiny non-expert minority are correct, you do not own the most basic requirement for being President.
The ability to make a decision based on information from experts is a PRIMARY JOB REQUIREMENT and they show they can’t do it when they deny manmade climate change.
Some of the climate change deniers may actually believe the climate change science, but are willing to take the denier stance because its politically in their best interest.
The second great indicator of a leader is the ability to do the right thing even when this might not work in their personal interest. In other words integrity. This one is where probably the entire field for 2016 fails, but its hard to pick out unless they deny climate change.
So if the Presidential Candidate is a climate change denier he/she is either unable to make good decisions based on evidence from experts – ie their entire prospective job, or they have integrity problems, which means nothing they say can be relied on.
Its a red flag for me. Climate Change Denier = NOPE.