The Climate-Independent Need for Renewable Energy in the 21st Century

In December 2015 the nations of the world agreed, in principle, to limit global warming to no more than 2 ◦C above pre-industrial levels. In order to achieve this goal, recent publications have shown that (1) more than 50% of known fossil fuel reserves need to remain unused, and (2) the timing of the transition away from fossil fuels needs to achieve 50% renewable energy by 2028, an expansion of renewable sources of 37-fold in the next 12 years. This rate of expansion is unprecedented and unlikely to be achieved. Even utilizing the 50% of fossil fuels untapped in a <2 ◦C scenario results in significant expansion of renewable energy sources by 2100. Here we examine three fossil fuel reserve estimates and two per capita energy consumption tracks to understand how dominant renewable energy sources need to be during the second half of the 21st century. We find that per capita energy consumption rates are a more significant factor in the demand for renewable energy infrastructure, as wide ranging estimates of fossil fuel reserves still result in peak production by mid-century. At either of the consumption rates, attempting to uphold the 2 ◦C global warming goal would demand more energy from renewable sources than was produced from all sources in 2014. In total, the world will likely require between 600 and 2000 exajoules of renewable energy by the year 2100, a significant expansion from the 13 produced in 2014. Despite meaningful gains in renewable energy sources, the transition away from fossil fuels is not keeping pace with rising global population, and expansion of global per capita consumption. Even in the absence of global warming concerns, renewable energy infrastructure needs to immediately begin significant expansion.