1.1 'Big picture' -some trends urged by net zero Transition to net zero requires drastic changes across many industries, which is difficult to realize in a short period of time. Net zero will not happen spontaneously, and it largely relies on policies. So far, over 130 countries have pledged to their national net-zero targets, 1 but few pledges are backed up by legislation or detailed policies. From the existing policies to stricter schemes, International Energy Agency (IEA) presents three scenarios 2 for the prediction of global energy sector through 2050, as shown in Figure .