The global warming phenomenon is so complicated that a systematic approach is required to study technological options for its mitigation, and the mitigation technology development usually takes so long a time and so large an investment that prudential evaluation should be made for its effective development.  We have developed a global energy system model of optimization type, DNE (Dynamic New Earth) 21.   A brief description of the model will be given, and analysis results will be shown with respect to energy system optimization under constraints of CO2 concentration.  We have just started to develop an evaluation system of technology developments for the global warming mitigation and our intention and planning are introduced together with the methodology.