Date of Award

January 2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Space Studies

First Advisor

Paul S. Hardersen

Abstract

To determine the capability of NASA's GISS GCM-II global climate model, the user-friendly EdGCM interface to the 3-D climate model code was evaluated by simulating global climate patterns that Earth-like planets may experience. The simulation scenarios involved different greenhouse gas emissions trends, planetary orbital parameters, and solar irradiance variations. It is found that the EdGCM interface to the GCM-II 3-D climate model is capable of studying climate patterns on hypothetical Earth-like planets, with some limitations involved. Studying extreme climate patterns on Earth-like planets as a function of planetary obliquity, orbital eccentricity, atmospheric composition, solar irradiance variations, and location with the host star's habitable zone is needed to determine whether such planets are habitable for life as we know it. Studying the behavior of climate on hypothetical Earth-like planet also provides insight into the future climate of our own planet. A database of climate models based on hypothetical Earth-like worlds will provide a valuable resource to the astrobiology community in support of future detections of exoplanets with masses, sizes, and composition similar to Earth. At present, most studies involved the use of 1-D, or 2-D climate models to explore planetary climate on Earth-like planets. This is due to the difficulty of using very complex 3-D climate model codes that typically have poor user interfaces or interfaces that are very difficult to use. EdGCM provides scientists with a user-friendly interface to a full 3-D climate model capable of simulating the climate on Earth-like planets. However, EdGCM is extremely limited in studying global climate on exo-Earth planets outside our solar system. The user is able to change the simulation initial conditions, including different greenhouse gas concentrations and their associated trends, solar irradiance and its trend over time, planetary obliquity and orbit eccentricity, and heliocentric distance by specifying the appropriate solar irradiance. The results of simulations carried out in this research indicate positive results, with the exception of some of the more extreme cases. The EdGCM interface to GCM-II would be a valuable addition to universities with astrobiology programs involved in studying climate on Earth-like planets with one major modification. The ability to change the land mass configuration that is currently based on Earth's continents to any arbitrary land mass configuration would allow the creation of a database of climate model simulations of an array of hypothetical Earth-like worlds that will soon be discovered by current and future space-based planet-finding missions.

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