Marine heatwaves (MHWs) and marine cold spells (MCSs) can have devastating impacts on the environment. We analysed their trends and found that the number of MHWs and MCSs is increasing and decreasing respectively, except for an area of the Southern Ocean where MCSs are increasing. While our results are in agreement with previous studies, this study uses a different, higher-resolution sea surface temperature dataset, showing that these events are not just a feature of their input dataset.