A carbon tax essentially considers all carbon emissions harmful to the environment, and warranting of equal punishment so is therefore fairer. A cap-and-trade system only punishes carbon emissions above a certain level, treating only certain kinds of emissions as "bad". A carbon tax, therefore, sends a strong message to polluters that all their emissions are harmful, that they should be phased out, and that they should invest in environmentally-friendly sources of energy. This dramatic message may be particularly important if we view global warming to be a serious crisis.  Companies are even willing to pay a premium for the stability provided by this system [I1] ; the premium being the tax itself, and the lack of the potential for profit through the trading of carbon credits. Further as a system that is easy to understand it is easier for directors to allow their firms to ease in to the system. [1]  [1] Ugur Akinci, “Carbon Tax Versus Cap And Trade Approaches to Global Warming – Part 1.” Doubletaxes.com 2007   [I1] Examples and case studies required.