The paper reviews global trends of climate change response, policies of the government of Japan to realize carbon neutrality, scenario analyses of 2050 carbon neutrality by RITE（Research Institute of Innovative Technology for the Earth）, and important roles of innovations both in technologies and social systems. Global responses to climate change started by the Earth Summit in 1992, followed by the first international framework of the Kyoto Protocol, and now by the Paris Agreement. The goal of climate response has been made more ambitious, now, many countries including Japan set the goal as carbon neutrality in 2050. The scenario analysis done by RITE for 2050 carbon neutrality suggests that we should mobilize various technologies to realize the ambitious goal, not only energy savings, nuclear, renewables, but also hydrogen/ammonia, CCS, oversea CO2 reservoir, synfuels, and negative emission technologies. Japanese government is promoting green transformation (GX) policies to realize both carbon neutrality and economic growth through various innovations. Among the innovations, demand-side approaches such as circular/sharing economies are very important for realizing revolutionary energy savings through electrification and digitalization of energy system. Globally united action is indispensable because climate change is a global risk.