Why? Both beliefs are held against current scientific consensus and have only a few supporting studies, while vast majority of studies support the contrary.

You could argue that technically "climate change scepticism" only means you don't know, but in practice climate change sceptics argue for political actions (or inaction) basing on their (lack of) beliefs.

Similarly I can be anti-vacc without claiming "vaccines cause autism". just claiming "I'm not sure what they cause, so just to be sure don't do it".

The science in favor of vaccination is very straightforward and well-understood. It's easy to run double-blind tests and determine the truth of the matter.

The science in favor of anthropogenic global warming includes two parts: well-understood physics and chemistry (which is quite trustworthy and is actually science), and a bunch of conflicting computer models of a chaotic and poorly understood system with a huge number of inputs and feedback loops (which I'm not sure why anyone trusts).

This blog post puts it pretty well: http://blog.dilbert.com/post/158778029326/how-to-change-my-b...