Quantifying the reduction in coal and increase in renewables in OECD (Organisation for Economic Co-operation and Development) countries: Proposal for a coal-renewable energy index and map

Reducing coal use and increasing renewable energy use are two major policies that have been recommended in many countries and regions to address climate change. However, the progress toward meeting these policy goals is unclear. Therefore, this study proposes the “C–R map”, which is a correlation map between the share of coal-fired plants and renewable energy in terms of annual consumption, and the “CR index”, which is an index composed of the above two indicators. The proposed methods objectively visualise and quantitatively analyse statistical data on global climate change associated with “reducing coal and increasing renewables”, whose trends or tendencies could only be obtained through fragmented statistical data and documents. Using the proposed C–R map and CR index, an international comparative analysis was conducted on the share of coal and renewables from 1990 to 2020 in 37 Organisation for Economic Cooperation Development member countries. The results quantitatively showed that 31 member countries clearly exhibited a trend of decreasing their share of coal and increasing their share of renewables, while only five countries, i.e. Chile, Turkey, Mexico, Japan, and Korea, showed unique and inconsistent trends relative to that of the other member countries. By using the highly transparent and simple map and index proposed here based on published statistical information and objective methods, the global trend of “reducing coal and increasing renewables” can be quantitatively visualised in graphs and numerical values, which are easily understood and interpretable, even for laymen.