1990

2000

2010

2020

Vol. Difference (After less Before)-mm

−750

−710

−790

−720

Sum of fluxes (mm)

−737

−687

−788

−710

Error (mm)

−13

−23

−2

−10

Error (%)

1.8

3.2

0.3

1.4

Accuracy (%)

98.2

96.8

99.7

98.6