Lukewarmers. Or, if they're English, 'Mildforthetimeofyearers'.
Ha!
Of course there is a wide middle ground of people who feel obliged to say "I believe in AGW, of course I do!", who are really just going with what they feel the crowd is going with. In reality they are going with what heavy, heavy funding of propaganda instructs them to go with.
This is actually evident in the statements themselves. Why is it felt necessary to state the beliefs? It is in fact like one of the fundamental characteristics of many Christians, to ask others, shortly after meeting them, if they are Christian. And then, the other person is judged as good or bad.
Going to more diehard Warmers, one thing that is often seen is a denial of contrary facts and evidence. Thus Pixel42 will continue to present as a good study in AGW the free university course, when in fact it is a very biased and scientifically unsound course in my opinion. There is for example in this reference a "right or wrong answer" to the question "Explain how we helping to drown people in Bangaldesh every time we heat up a cup of tea?".
Obviously, propaganda posing as an authentic question in a "textbook". When this is pointed out, there is some ducking and dodging. But then some time later, perhaps to a new audience, Pixel42 will again promote this reference.
Thus we have the category of "Closet Warmers", similar to gays in the closet. They can't or won't come out and admit it, but they are die hard warmers. Calling them warmers may be offensive, because it points to the negative and irrational parts of the belief system.
And certainly in polite conversation we don't make a habit of offending people.
Postscript:
There is a scientific possibility of global cooling, based on technical aspects of the Sun's sunspot patterns and what they are considered to functionally mean in terms of internal solar dynamics. These have begun to exhibit similarities to the patterns before and during the Little Ice Age several centuries ago. There is no way to assign a percentage probability with current understanding that I am aware of.
However - heavy AGW propaganda and resulting "right ways to think" and "right ways to believe" do interfere with with scientific assessments of oppossing, non politically correct trends. After setting up the "Denier" category, which relates to someone who does not believe whatever the user of the phrase believes, clearly someone looking at global cooling would be a Denier.
A one or two degree drop in global temperatures due to the Sun's natural cycles would be catastrophic. The world population is much higher than in the 17th century, when the Little Ice Age occurred. Cooling would be worse than warming (there are ten times the deaths due to climate in cold weather, than warm weather). Numerous peer review articles have described the relevant solar issues and how global cooling could occur. But these do not get traction in the media or politics because they require a spirit of free inquiry, which is contrary to the operation of a propaganda machine.
Just another factoid against preconceived and rigid belief patterns, their promotion through paid propaganda in the media through vested business interests, coupled with complicit political schemes geared primarily to raise tax revenues under a nice "green" cloak.