[From 19th to 20th century: Natural disasters and man-made disasters]

This paper discusses a number of historical events in the 20th century from the point of view of human suffering in demographic terms, and also examines briefly the role of science and technology in these events. On the basis of this discussion it is concluded that two priorities for humanity in the 21st century are preventing climate change from reaching catastrophic tipping points, and avoiding a new world war. In both of these endeavors the scientific community can and must have a prominent role.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61413/1/Del_siglo_XX_al_siglo_XXI_-_Desastres_naturales_y_desastres_de_origen_humano_(Apuntes_de_CyT).pd