The increasing level of atmospheric carbon dioxide has driven public discourse throughout the world. An immediate implementation of carbon-free energy sources is demanded with little discussion of costs, technical constraints on the sources, or implications of high residual levels of carbon dioxide. Residual carbon-dioxide can be removed from the air, but the cost to remove the carbon-dioxide produced by human activity during a year is thought to be trillions of dollars—otherwise it remains in the atmosphere for centuries. Economic considerations may limit wind and solar sources to less than 40% of the electricity production. Fission or fusion may be the only choice for most of the rest. Development costs are orders of magnitude smaller than implementation costs, which are tens of trillions of dollars for fission. A needless delay in the development of fusion has enormous financial implications. As will be shown, stellarators are better positioned than any other concept for a fast path to fusion. A computationally derived conceptual design for a stellarator reactor may allow final design and construction to be initiated without the delay of intermediate generations of experiments. The most urgent issue is the development of conceptual designs.