The following graph illustrates schematically the difference between skepticism and contrarianism. The horizontal axis (the View of the World) represents a range of possible beliefs, such as the rate of rise of global temperature or the relative importance of human activities in driving global warming. The vertical axis (the Strength of View) represents the vigour with which each particular view is held - this may, for example, be measured by counting the number of people or publications that agree with a particular view.
The range of views held by most experts is indicated by the green (consensus) curve. As an example, this could be the statement by the Intergovernmental Panel on Climate Change (IPCC), in its Third Assessment Report (2001), that the global average temperature rose by 0.6 +/- 0.2°C, where the horizontal position of the peak of the green curve would represent 0.6°C and the width of the curve would represent +/-0.2°C.
The blue curve represents the range of beliefs held by skeptics. This generally involves less total "strength" than the consensus view (i.e. less people or publications would subscribe to it) and it covers a wider range that the consensus view. It is important to notice that skepticism covers regions on both sides of the range of consensus views. Skepticism is a necessary "check" to prevent the consensus or "orthodox" position becoming too narrow. It also permits science to follow paths that may not be immediately obvious at the time - i.e. it encourages lateral thinking. Another important faculty of skeptics is that they are as skeptical of their own opinions as they are of the opinions of others. In an ideal world, all scientists would be "skeptical" and the green and blue curves would be merged into one.
The red curve represents the range of beliefs held by contrarians. Firstly, these views are generally held by a minority (which does not, of course, mean that they are therefore wrong). However, more importantly, they represent a narrow range of views biased to one side of the range occupied by consensus and skepticism. In contrast to skepticism, contrarianism is unhelpful, as it distorts the opinions of policymakers and the general public (it is often give a disproportionate level of media exposure). It also often diverts scientists away from the "main game" to answer criticisms which are based more on a preconception that "the world has to be this way" (e.g. that "the Earth is just too big for us to have an impact on it") than on the best available science.
A good way to test whether a particular range of views is "skeptical" or "contrary" is to ask two questions: