It is exactly clear what climate change denialists are denying: They are denying that humans should do something about reducing greenhouse gas emissions. There are a number of different ways to 'implement' that denial, such as denying that climate change is happening in the first place or denying that humans are causing it, but it always leads to the same conclusion, and therefore - I am suspecting - always has the same motivation: Intellectual laziness, not wanting to rethink one's own lifestyle.