What changed when NOAA updated their time series record in 2025?

• With the recent calibration of data, on average, the severity level of annual blooms since 2013 has been lowered. For example, the formerly classified “severe” bloom in 2021 will now be classified as a “moderately severe” bloom.
• 2011 and 2015 are still considered “very severe” blooms (i.e., greater than 7 on the index), but have swapped places in terms of their rank. 2011 has regained the title of being the worst year on record, a 10 out of 10 on the severity index.