The chart shows changes in sea surface temperature (SST) by comparing the average of the most recent two weeks with the average of the preceding two weeks. This is used to monitor short-term warming or cooling trends in the ocean, which are important factors affecting weather conditions. Warm colors (yellow/orange/red) indicate areas where SST has increased (positive values), while cool colors (light blue/blue) indicate areas where SST has decreased (negative values) compared to the reference period.