Most studies focus on the impact of climate change on the mean state of phytoplankton and primary productivity, but little is known about whether and how climate change is impacting variance and extremes. In this study, we assess changes in chlorophyll-a concentration (CHL), which is an important proxy for primary production of marine ecosystems. Previous study suggests a decreasing variability in phytoplankton chlorophyll in both observational period and the model ensemble [1]. Our objective is to understand whether and how climate change impacts the whole distribution of variability in primary productivity. We utilize a series of statistical methods and reanalysis of CHL datasets to assess the variance and extremes of all distributions of CHL.