Ergo, the quantitative relationships ranging from ITCZ location and AHT

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(2008) in a slab ocean aquaplanet simulation where a hemispheric asymmetry in atmospheric heating was imposed by introducing a surface heating in the southern extratropics and an equal surface cooling in the northern extratropics. The ITCZ was found to shift toward the heat source and the precipitation maximum was nearly collocated with the location of zero meridional heat men seeking women for sex transport in the atmosphere, suggesting that a meridional shift of the Hadley cell was the underlying cause of the precipitation shift. Yoshimori and Broccoli (2009, 2008) found that the change in AHT_EQ in response to hemispheric asymmetric forcing was closely related to the meridional shift in the Hadley cell, which itself was a response to the hemispheric asymmetry of the forcing and feedbacks. They also noted the concurrent shift in the tropical precipitation along with the Hadley cell but did not quantify the relationship between the change in AHT_EQ and the meridional shift of the ITCZ. More recently, Frierson and Hwang (2012) found that the meridional shift in the ITCZ due to increased greenhouse gas concentrations in an ensemble of simulations was strongly correlated with the change in AHT_EQ. They also found that AHT_EQ had a large intermodel spread due to differences in extratropical cloud responses. This suggests that the extratropics play an important role in setting the ITCZ location via the interhemispheric asymmetry in energy input to the atmosphere and the associated changes in AHT_EQ.

There is widespread paleoclimatic evidence for shifts and/or intensity changes of tropical precipitation in the past including a southward shift of the ITCZ during glacial times (Pahnke et al. 2007), abrupt transitions during glacial times (Wang et al. 2001; Peterson et al. 2000) associated with Dansgaard–Oeshchger and Heinrich events, a more northern location during the Holocene thermal maximum (H), and a southward shift (estimated to be approximately 5°) during the Little Ice Age (Sachs et al. 2009). Provided the same relationship between the ITCZ and AHT_EQ holds across different climate states, each of the ITCZ shifts noted in the paleoclimate records would have an AHT_EQ change that can be quantified. Moreover, the change in AHT_EQ would have to be associated with a hemispheric asymmetry of atmospheric forcing or climate feedbacks (see Fig. 2). _EQ provides a framework for comparing precipitation shifts deduced from paleoclimate data and the proposed mechanisms and/or climate forcing that are believed to have caused the precipitation changes (i.e., orbital forcing, changes in land ice and sea ice, cloud albedo changes, a shutdown of the Atlantic meridional overturning circulation, etc.). There is also widespread paleoclimatic evidence for changes in meridional gradients of tropical sea surface temperature (SST) to which the ITCZ is sensitive. Furthermore, SST gradients may be easier to reconstruct from paleoproxies than ITCZ location. Therefore, a quantification of the relationship between SST gradients and ITCZ location is an important task for paleoclimate interpretation.