A high value indicates that the project turned out better than the model predicted, while a
negative error value indicates that the project turned out worse than it predicted.
The uncertainty /
error values, from those groups that provided them, are about 0.4 million square kilometers, thus many of the values essentially overlap.
The absolute
error values may seem high, but it is important to note that each year has roughly the same absolute error value, so the decline over the long term remains clear.