Effects of recent energy system changes on CO2 projections for the United States

Abstract

Recent projections of future United States carbon dioxide (CO) emissions are considerably lower than projections made just a decade ago. A myriad of factors have contributed to lower forecasts, including reductions in end-use energy service demands, improvements in energy efficiency, and technological innovations. Policies that have encouraged these changes include renewable portfolio standards, corporate vehicle efficiency standards, smart growth initiatives, revisions to building codes, and air and climate regulations. Understanding the effects of these and other factors can be advantageous as society evaluates opportunities for achieving additional CO reductions. Energy system models provide a means to develop such insights. In this analysis, the MARKet ALlocation (MARKAL) model was applied to estimate the relative effects of various energy system changes that have happened since the year 2005 on CO projections for the year 2025. The results indicate that transformations in the transportation and buildings sectors have played major roles in lowering projections. Particularly influential changes include improved vehicle efficiencies, reductions in projected travel demand, reductions in miscellaneous commercial electricity loads, and higher efficiency lighting. Electric sector changes have also contributed significantly to the lowered forecasts, driven by demand reductions, renewable portfolio standards, and air quality regulations.

Evolution of the United States Energy System and Related Emissions under Varying Social and Technological Development Paradigms: Plausible Scenarios for Use in Robust Decision Making

“…Projections can change significantly even in a decade. 27 The life cycle of fossil fuels, including extraction, processing, and use, is the primary source of most air pollutants and greenhouse gas emissions in the U.S. 28 Thus, baseline emissions are dependent on assumptions about future energy demands, as well as technologies and fuels that will be used to meet those demands. Factors influencing the evolution of the energy system include population growth and migration, economic growth and transformation, climate change, technology change, land use change, fuel price and availability, consumer choices, and policy drivers.…”

“…The use of longer time horizons also yields a challenge: greater uncertainty in the baseline itself. Projections can change significantly, even in a decade . The life cycle of fossil fuels, including extraction, processing, and use, is the primary source of most air pollutants and greenhouse gas emissions in the United States .…”

“…Projections can change significantly, even in a decade. 27 The life cycle of fossil fuels, including extraction, processing, and use, is the primary source of most air pollutants and greenhouse gas emissions in the United States. 28 Thus, baseline emissions are dependent on assumptions about future energy demands as well as technologies and fuels that will be used to meet those demands.…”