There is a strict process before anyone can be termed a denier:
1) Something has to be known to exist
2) The person then claims it does not, even though it does and can be proved to do so.
There are no other conditions.
So, for example there is no possible doubt about who died in the holocaust. We have the bodies, names and records as well as photos and reports from soldiers who liberated them and many survivors. But plenty of people deny it happened, so they must be deniers as no other term can apply to them. That is the meaning.
Therefore as the CO2 alone can only supply 1C at 520ppm and has supplied around .4C at 400 (the rest of the rise is natural), what could make it suddenly start adding more to exceed 2C? We don't know. Therefore those claiming we do are exaggerating based on no more than one of many possible alternatives, although given over 150 years to observe, none of them have happened, in fact the water vapour required to cause the added rise has reduced, instead forming clouds which cool, as demonstrated in the negligible warming in response to a 50% rise in CO2.
Therefore no one is or can be denying anything in dangerous global warming if they don't agree it's