Séminaire
The SST contrast between the northern and southern hemispheres influences the location of the ITCZ and the intensity of the monsoon systems. From the late 1960s — early 1970s, the interhemispheric SST contrast experienced a rapid north–south shift, which had pronounced impacts on rainfall in the Sahel and other regions. I will discuss results from a detection & attribution study using CMIP5 models to quantify the contributions of external forcing and unforced internal variability to the interhemispheric SST contrast during the instrumental period (1881–2012). The late 1960s – early 1970s shift is found to be largely due to internal variability, with a smaller contribution from anthropogenic aerosols. Some models are able to produce such large-magnitude shifts in their control simulations, suggesting that the late 1960s – early 1970s shift is within the range of background climate variability. I will also discuss some of the patterns producing large-magnitude interhemispheric SST shifts.
helene.rouby@ens.fr