These models
consist of connected sub-modules that deal with radiative transfer, the
circulation of the atmosphere and
oceans, the physics
of moist convection and cloud formation, sea ice, soil moisture and the like.
By examining the spatial pattern
of both types
of climate variation, the scientists found that the anthropogenic global warming signal was relatively spatially uniform over the tropical
oceans and thus would not have a large effect on the atmospheric
circulation, whereas the PDO shift in the 1990s
consisted of warming in the tropical west Pacific and cooling in the subtropical and east tropical Pacific, which would enhance the existing sea surface temperature difference and thus intensify the
circulation.