"Uncertainty levels" refers to the amount of doubt or lack of certainty in a situation or information. It measures how confident or unsure we are about something. Full definition
He notes that the paper has very large uncertainty levels on the graph detailing the key findings of the paper (see figure above). (scientificamerican.com)
It's the average that's meaningful, because the process of averaging reduces the inherently large uncertainty level. (realclimate.org)
The huge spike is the huge uncertainty level of the final two data points — April and May 2010. (tamino.wordpress.com)