MARKAL was developed in a cooperative multinational project over a period of almost two decades by the Energy Technology Systems Analysis Programme (ETSAP) of the International Energy Agency.
Itself a model for compliance with the UN Framework Convention on Climate Change, ETSAP offers:

The basic components in a MARKAL model are specific types of energy or emission control technology. Each is represented quantitatively by a set of performance and cost characteristics. A menu of both existing and future technologies is input to the model. Both the supply and demand sides are integrated, so that one side responds automatically to changes in the other. The model selects that combination of technologies that minimizes total energy system cost.

Thus, unlike some "bottom-up" technical-economic models, MARKAL does not require -- or permit -- an a priori ranking of greenhouse gas abatement measures as an input to the model. The model chooses the preferred technologies and provides the ranking as a result. Indeed, the choice of abatement measures often depends upon the degree of future abatement that is required.

Typically, a series of model runs is made examining a range of alternative futures. The model requires as input projections of energy service demands -- room space to be heated or vehicle-miles to be traveled, for example -- and projected resource costs. Then, a reference case is defined in which, for example, no measures are required to reduce carbon dioxide emissions. A series of runs is then made with successive reductions in emissions: emissions stabilized at present levels, for example, then reduced by 10 percent, 20 percent, etc., by some future date before being stabilized.

In each case, the model will find the least expensive combination of technologies to meet that requirement -- up to the limits of feasibility -- but with each further restriction the total energy system cost will increase. Thus, the total future cost of emission reductions is calculated according to how severe such restrictions may become. These can be plotted as continuous abatement cost curves. In addition, the marginal cost of emission reduction in each time period is determined.

This is of special interest in establishing abatement policy because it can be interpreted as the amount of carbon tax that would be needed to achieve this level of abatement.

Some uses of MARKAL: