COP21 is not a solution in itself for nations; it establishes a benchmark of carbon reduction targets without prescribing specific economic methods.
COP21 represented an initial and relatively modest step, with limited carbon-reduction targets, aimed at placing all economies on a common path toward global economies of scale that enable painful emissions cuts. COP21 serves only as a benchmark; each nation remains responsible for developing its own strategies to meet the agreed-upon targets.
The full phase-out of fossil fuels is targeted for 2050, a commitment that can only be credible if near-term goals are successfully achieved; however, subsequent COP negotiations have faced significant challenges, slowing progress toward establishing serious national objectives and toward compensation or technology transfers for developing nations.