Assessment of technological options in the global energy system for limiting the atmospheric CO2 concentration

The purpose of this study was to assess comprehensively the technological measures for limiting CO2 concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system and then to sketch concrete scenarios for the desirable future development of the global energy system over the next century. To facilitate the assessment, we developed a large-scale energy system model Dynamic New Earth 21 based on the New Earth 21 model. The Dynamic New Earth 21 model has been developed to cope with newly emerging research topics, such as an integrated assessment of climate change. This paper presents the latest numerical results of this model and its outlined descriptions. In the framework of this energy model, the world is divided into 10 regions so we can evaluate the differences in regional economic and geographical conditions. The model can assess the various technological options up to the year 2100, optimizing intertemporally the sum of the discounted total energy system costs. As specific technological options, the model takes into account the following categories of technologies: energy-saving in end-use sectors, efficiency improvement in energy conversion sectors, utilization of various less carbon-intensive energy resources, disposal and recycling of CO2 recovered in the energy systems, and innovative system technologies especially with respect to hydrogen use. The results of the study suggest that the CO2 problem cannot be easily settled by any single technological option, but they also suggest that if those options are reasonably combined with one another there is technological potential for CO2 emission reduction. For limiting atmospheric CO2 concentrations to less than 550ppm over the next century, the computed optimal CO2 emission trajectory indicates that relatively modest abatement actions are expected in the near future, implying that immediate CO2 emission reduction or stabilization strategies will not necessarily lead to economically efficient outcomes.