In each experiment, the change in annual mean PCent and AHTEQ changes are significantly negatively correlated among the ensemble members with an average correlation coefficient of ?0.81 and a correlation coefficient of ?0.85 when considering all experiments collectively. The regression coefficient between PCent and AHTEQ ranges from ?4.dos° PW ?1 in the 2XCO2 ensemble to ?3.2° PW ?1 in the LGM and 6Kyr ensembles (Table 3) and the regression coefficient of all simulations considered simultaneously is ?3.2° PW ?1 . Penny and AHTEQ of ?2.7° PW ?1 found in the observations. These results collectively suggest that the relationship between PCent and AHTEQ is robust across time scales (seasonal vs annual mean) and across different climate states. We return to this point in the discussion section.
The intermodel spread in annual mean PCent and ?SST changes are significantly positively correlated in all three perturbation experiments with an average correlation coefficient of 0.86 and a slope that ranges from +1.5° K ?1 in the LGM simulations to +2.4° K ?1 in the 6Kyr experiments (Table 3). These slopes are significantly shallower but of similar magnitude to that found in the seasonal cycle in the observations (+3.3° K ?1 ).
1) 2XCO2 experiments
The ITCZ response to CO2 doubling in the CMIP3 slab ocean simulations was analyzed thoroughly by Frierson and Hwang (2012), who concluded that there are large intermodel differences in the annual mean ITCZ shift due to differences in the AHTEQ change that primary reflect intermodel differences in extratropical feedbacks. (more…)