Premium
Sensitivity of a coupled atmosphere‐dynamic upper ocean GCM to variations of CO 2 , solar constant, and orbital forcing
Author(s) -
Syktus Jozef,
Gordon Hal,
Chappell John
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl01014
Subject(s) - solar constant , atmospheric sciences , forcing (mathematics) , orbital forcing , atmosphere (unit) , environmental science , latitude , climatology , northern hemisphere , middle latitudes , geology , physics , solar irradiance , meteorology , insolation , geodesy
Sensitivity of a coupled atmosphere‐dynamic upper ocean GCM to varying CO 2 , solar constant, and orbital forcing was examined. Response to atmospheric CO 2 concentrations ranging from 100–3500 ppm is logarithmic at all latitudes and seasons, with highest sensitivity at high latitudes, during the winter season. Solar constant response is approximately linear over the range of values +2%, but the sensitivity at high latitudes is less than for equivalent CO 2 forcing. Sensitivity to “cold northern summer” orbital forcing, which occurred at the start of the last glacial cycle, is strongly affected by CO 2 . For CO 2 at or below the present level, perennial snow cover in the northern hemisphere expands dramatically with “cold summer” orbital forcing, but this effect becomes very small for CO 2 levels in the range 410–460 ppm. This result suggests that the Quaternary “ice age” mode of climatic behaviour may have been initiated by an atmospheric CO 2 decrease below a critical value, probably around 350–450 ppm.