Comparison of the Earth-twin MIR emission spectra calculated with various different models. We plot the photon flux received from an Earth-twin located 10 pc from the sun. The solid blue line is the MIR thermal emission calculated with petitRADTRANS using the settings discussed in Sect. 2.3.1. The blue-shaded region indicates the most optimistic LIFEsim uncertainty (S/N = 20) used in our retrievals. The red dashed line represents a cloud-free Earth model by Daniel Kitzmann (priv. comm.), which takes scattering into account. The green and black dashed-dotted lines are the cloudy (60% cloud coverage) and cloud-free modern Earth spectra from Rugheimer et al. (2015) that account for scattering.