Pathways to Deep Decarbonization in the United States

Limiting the anthropogenic increase in global mean surface temperature to less than 2 degrees Celsius (°C), an objective agreed upon by the international community, will require that global net GHG emissions approach zero by the second half of the 21st century. The principal finding of this study, conducted using the PATHWAYS and GCAM models, is that it is technically feasible to achieve an 80% greenhouse gas reduction below 1990 levels by 2050 in the United States (U.S.), and that multiple alternative pathways exist to achieve these reductions using existing commercial or near-commercial technologies. Reductions are achieved through high levels of energy efficiency, decarbonization of electric generation, electrification of most end uses, and switching the remaining end uses to lower carbon fuels. The cost of achieving these reductions does not appear prohibitive, with an incremental cost to the energy system equivalent to less than 1% of gross domestic product (GDP) in the base case. These incremental energy system costs did not include potential non-energy benefits, for example, avoided human and infrastructure costs of climate change and air pollution. The changes required to deeply decarbonize the economy over the next 35 years would constitute an ambitious transformation of the energy system. However, this study indicates that these changes would not necessarily entail major changes in lifestyle, since the low carbon pathways were designed to support the same level of energy services and economic growth as the reference case based on the U.S. Department of Energy’s Annual Energy Outlook. Starting now on the deep decarbonization path would allow infrastructure replacement to follow natural replacement rates, which reduces costs, eases demand on manufacturing, and allows gradual consumer adoption.

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