The IronEx studies showed that in situ addition of iron in “high-nitrate-low-chlorophyll” regions of the Pacific Ocean increased the amount of dimethylsulfide (DMS) available for emission to the atmosphere. Here we show results from two similar experiments in the Southern Ocean (SOIREE, 61°S and EisenEx, 48°S). DMS concentrations increased up to 8-fold and we find marked similarity in the changes in dimethylsulfonioproprionate (the algal precursor of DMS) during the Pacific and Southern Ocean experiments, despite large differences in algal community, temperature, light and mixed layer depth. These results may lend support to a link between paleo-climatic variations in iron availability, emissions of DMS and, hence, atmospheric albedo and global temperature. Further, if large-scale iron fertilization is to be considered as a strategy for mitigating the increase in man-made CO2 in the atmosphere then the climatic affects of DMS and a number of other trace gases must be assessed.