The uncertainty of climatological values is calculated with a method using the average absolute deviation from the mean, or absolute error. This method is related to the mean of the magnitude of the anomalies and its applicability is readily verified with a proposed approximate numerical technique, in contrast with the standard error method whose applicability is cumbersome to verify. Different data sets were tested with this technique showing that the method applies in a wide variety of geophysical cases, including non-Gaussian cases. When it applies, the absolute error method provides additional information on the mean, such as the error due to the sample size.