Investigation of the Archean climate using the NCAR CCM

摘要

The Archean (2.5 to 3.8 billion years ago) is of interest climatically because of the 'Faint Young Sun's Paradox,' which can be characterized by the Sun's reduced energy output. The lower energy output leads to a frozen planet if the climate existed as it does today, but the geological record shows that water was flowing at the earth's surface 3.8 b.y. ago. Energy balance models predict a frozen planet for this time period, unless CO2 concentrations exist in the Archean atmosphere. The thesis explores the Archean climate with the Community Climate Model. A series of sensitivity simulations were undertaken which first explores individual factors that may be important for the Archean. They include rotation rate, lower solar luminosity, and land fraction. Then these climatic factors, along with higher CO2 concentrations, are combined into a set of experiments. The conclusions are (1) that large CO2 concentrations in the Archean atmosphere are not necessary to obtain an equitable climate, (2) that a faster rotation rate causes a large reduction in clouds, and (3) that atmospheric dynamics are large components of the climate system and cannot be ignored.