| Abstract: This lecture evaluates the low-frequency variability
of surface air temperature that was obtained from a 1000-yr integration
of a coupled ocean-atmosphere-land surface model. The model simulates reasonably
well the variability of local and global mean surface air temperature (SAT)
at decadal timescales. The physical mechanisms responsible for this variability
are explored. Based upon an analysis of the time series of the simulated
global mean SAT, it is indicated that the warming trend of ~0.5
degrees C century-1 since the end of the
last century was not generated internally through the interaction among
the atmosphere, ocean, and land surface. Instead, it appears to have been
induced by a sustained change in the thermal forcing such as that resulting
from changes in atmospheric greenhouse gas concentration, solar irradiance,
and aerosol loading. |