影像來源/ SOURCES: "METAL REQUIREMENTS OF LOW-CARBON POWER GENERATION," BY REN KLEIN ET AL., IN ENERGY, VOL. 36, NO. 9; SEPTEMBER 2011 (COLORED CIRCLES); "ENVIRONMENTAL RISKS AND CHALLENGES OF ANTHROPOGENIC METALS FLOWS AND CYCLES: A REPORT ON THE WORKING GROUP ON THE GLOBAL METAL FLOWS TO THE INTERNATIONAL RESOURCE PANEL," BY E. VAN DER VOET ET AL. UNEP, 2013 (GREENHOUSE EMISSIONS BY METAL) ; GRAPHIC BY ARNO GHELFI
