| Autor: |
Del Genio AD; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA., Kiang NY; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA., Way MJ; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA., Amundsen DS; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.; Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA., Sohl LE; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.; Center for Climate Systems Research, Columbia University, New York, NY 10027, USA., Fujii Y; Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro, Tokyo 152-8550, Japan., Chandler M; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.; Center for Climate Systems Research, Columbia University, New York, NY 10027, USA., Aleinov I; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.; Center for Climate Systems Research, Columbia University, New York, NY 10027, USA., Colose CM; NASA Postdoctoral Program, Goddard Institute for Space Studies, New York, NY 10025, USA., Guzewich SD; NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA., Kelley M; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.; SciSpace LLC, 2880 Broadway, New York, NY 10025, USA. |
| Abstrakt: |
The potential habitability of known exoplanets is often categorized by a nominal equilibrium temperature assuming a Bond albedo of either ∼0.3, similar to Earth, or 0. As an indicator of habitability, this leaves much to be desired, because albedos of other planets can be very different, and because surface temperature exceeds equilibrium temperature due to the atmospheric greenhouse effect. We use an ensemble of general circulation model simulations to show that for a range of habitable planets, much of the variability of Bond albedo, equilibrium temperature and even surface temperature can be predicted with useful accuracy from incident stellar flux and stellar temperature, two known parameters for every confirmed exoplanet. Earth's Bond albedo is near the minimum possible for habitable planets orbiting G stars, because of increasing contributions from clouds and sea ice/snow at higher and lower instellations, respectively. For habitable M star planets, Bond albedo is usually lower than Earth's because of near-IR H 2 O absorption, except at high instellation where clouds are important. We apply relationships derived from this behavior to several known exoplanets to derive zeroth-order estimates of their potential habitability. More expansive multivariate statistical models that include currently non-observable parameters show that greenhouse gas variations produce significant variance in albedo and surface temperature, while increasing length of day and land fraction decrease surface temperature; insights for other parameters are limited by our sampling. We discuss how emerging information from global climate models might resolve some degeneracies and help focus scarce observing resources on the most promising planets. |
