Year	Calculated data (based on in-situ measurements and remote sensing data)	Uncertainty	Upper error	Lower error	Lower uncertainty limit	Upper uncertainty limit
1985	8.109	0.00081699			8.108	8.11
1986	8.108	0.000789079			8.107	8.109
1987	8.107	0.000708053			8.106	8.107
1988	8.104	0.000893326			8.103	8.105
1989	8.103	0.000668776			8.102	8.104
1990	8.102	0.000823911			8.101	8.103
1991	8.101	0.000728206			8.1	8.102
1992	8.101	0.000654949			8.1	8.101
1993	8.1	0.000715966			8.099	8.1
1994	8.098	0.000689711			8.097	8.098
1995	8.096	0.000765317			8.095	8.097
1996	8.094	0.000658288			8.093	8.095
1997	8.094	0.000613007			8.093	8.094
1998	8.091	0.000743927			8.09	8.091
1999	8.088	0.000734212			8.087	8.089
2000	8.087	0.000618534			8.086	8.088
2001	8.086	0.000618557			8.085	8.086
2002	8.084	0.000628333			8.084	8.085
2003	8.082	0.000732485			8.082	8.083
2004	8.081	0.000710167			8.08	8.082
2005	8.079	0.00071636			8.078	8.08
2006	8.077	0.000740666			8.077	8.078
2007	8.075	0.000683862			8.075	8.076
2008	8.074	0.000689732			8.073	8.074
2009	8.073	0.000627885			8.072	8.073
2010	8.071	0.000759265			8.07	8.072
2011	8.069	0.000824223			8.068	8.07
2012	8.067	0.000737861			8.067	8.068
2013	8.065	0.000752955			8.064	8.066
2014	8.064	0.000703221			8.063	8.064
2015	8.062	0.000717608			8.061	8.063
2016	8.06	0.000765008			8.059	8.06
2017	8.058	0.000790167			8.057	8.059
2018	8.057	0.000740047			8.056	8.057