The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). III. Simulated Observables—the Return of the Spectrum

Abstract The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) is a community project that aims to quantify how differences in general circulation models (GCMs) could impact the climate prediction for TRAPPIST-1e and, subsequently, its atmospheric characterization transit. Four GCMs have participated THAI: ExoCAM, LMD-Generic, ROCKE-3D, and UM. This paper, focused on simulated observations, third part of trilogy, following analysis two land planet scenarios (Part I) aquaplanet II). Here we show robust agreement between spectra number transits estimated detect atmospheres. For cloudy ones, 5 σ detection CO 2 be achieved about 10 if atmosphere contains at least 1 bar . That can vary by 41%–56% depending GCM used predict terminator profiles, principally due cloud deck altitude, with ExoCAM LMD-G producing higher clouds than ROCKE-3D Therefore, first time, this work provides “GCM uncertainty error bars” ∼50% need considered future analyses transmission spectra. We also analyzed intertransit spectral variability. Its magnitude differs significantly GCMs, but within measurement uncertainties. THAI has demonstrated importance model intercomparison exoplanets paved way larger develop an meta-framework, namely, Climates Using Interactive Suites Intercomparisons Nested Exoplanet Studies.