Emissions Trading is a system of “capping and trading” emissions limits. The amount of emissions a Polluter can release into the atmosphere is capped, in the form of Government issued allowances. An allowance represents One metric tonne of emissions, "allowable", into the atmosphere. These allowances are like Securities that can be traded on Carbon markets, exchanges or the Emissions Trading Network, this produces flexibility on how to meet emissions reduction without sacrificing the overall emissions target, thereby fighting climate change and global warming at least cost to Society.