Assessment of CO2 reductions and economic impacts considering energy-saving investments

Using a global dynamic optimization model that includes a notion of endogenous energy-saving investments, economic impacts and energy-system changes are assessed under several policy cases where CO2 concentration is stabilized at the 450, 500, and 550 ppm levels by the year 2100. The effect of increased investments in energy-saving technologies on energy efficiency is derived exogenously from results of the AIM/Enduse model applied to Japan, then endogenized in the global dynamic optimization model. We find that with diffusion of energy-saving technologies, GDP loss during the 21st century falls from 2.5% to 2.1% in the 450 ppm case. The impact is small for the 550 ppm case, however, because a shift to low-carbon-intensive energies such as gas and renewable energies does not occur to a significant extent under this target.