This essay does not deny the 0.6-0.8°C increase in global temperature that took place during the 20th century. It tries to understand how and why this simple fact has been transformed into a militant social movement. A clue is found in Hanna Arendt analyses of ideologies (based on the nazi and soviet totalitarianisms). All the key features of an ideology are present in “warmism”: a monocausal explanation of everything and anything; a reference/reverence to “science”; a massiv