The overall energy required to sublimate the from the south polar ice cap was modeled by Zubrin and McKay in 1993. If using orbital mirrors, an estimated 120 MW-years of electrical energy would be required in order to produce mirrors large enough to vaporize the ice caps. This is considered the most effective method, though the least practical. If using powerful halocarbon greenhouse gases, an order of 1,000 MW-years of electrical energy would be required to accomplish this heating. However, if all of this were put into the atmosphere,