Response of Surface Climate to Precession across Different Continental Configurations and Background Climates

Precession affects climate through seasonal redistribution of local insolation. Yet, its effects on climate and their dependence on continental configuration and background climate remain unclear. Here we use a fully coupled model to conduct a series of simulations across five geological periods (0 Ma, 80 Ma, 230 Ma, 300 Ma, and 440 Ma) by altering precession from 270° to 90° (i.e., the boreal summer changes from aphelion to perihelion). Results show that climate changes in certain seasons may dominate the annual mean changes. Moreover, changes in surface climate show common features especially over land, independent of continental configurations and background climate. The low-latitude continents experience a strong Northern Hemispheric (Southern Hemispheric) cooling (warming) dominated by summer change due to the strengthening (weakening) of the summer monsoon, during which more (less) low and middle clouds reduce (increase) the insolation received at the surface. The increased precipitation further cools the surface by increasing heat loss through enhanced evapotranspiration, and vice versa. Changes over mid-latitudinal lands are generally opposite to those at lower latitudes due to opposite cloud changes. However, the changes depend on the background climate; when the background climate is cold, the effect of surface albedo due to land snow changes may overwhelm and reverse the effect of clouds. The climate responses of the polar regions depend on the continental configuration and are opposite between the north and the south. Among all five continental configurations, the present-day (0 Ma) continental configuration has the largest response over the mid- to high-latitude regions.