| Year | AllGHGs | Threshold | Minimum | Maximum |
|---|---|---|---|---|
| 1750 | 450 | 400 | 500 | |
| 1755 | 450 | 400 | 500 | |
| 1760 | 450 | 400 | 500 | |
| 1765 | 450 | 400 | 500 | |
| 1770 | 450 | 400 | 500 | |
| 1775 | 450 | 400 | 500 | |
| 1780 | 450 | 400 | 500 | |
| 1785 | 450 | 400 | 500 | |
| 1790 | 450 | 400 | 500 | |
| 1795 | 450 | 400 | 500 | |
| 1800 | 450 | 400 | 500 | |
| 1805 | 450 | 400 | 500 | |
| 1810 | 450 | 400 | 500 | |
| 1815 | 450 | 400 | 500 | |
| 1820 | 450 | 400 | 500 | |
| 1825 | 450 | 400 | 500 | |
| 1830 | 450 | 400 | 500 | |
| 1835 | 450 | 400 | 500 | |
| 1840 | 450 | 400 | 500 | |
| 1845 | 450 | 400 | 500 | |
| 1850 | 450 | 400 | 500 | |
| 1855 | 450 | 400 | 500 | |
| 1860 | 450 | 400 | 500 | |
| 1865 | 450 | 400 | 500 | |
| 1870 | 450 | 400 | 500 | |
| 1875 | 450 | 400 | 500 | |
| 1880 | 450 | 400 | 500 | |
| 1885 | 450 | 400 | 500 | |
| 1890 | 450 | 400 | 500 | |
| 1895 | 450 | 400 | 500 | |
| 1900 | 450 | 400 | 500 | |
| 1905 | 450 | 400 | 500 | |
| 1910 | 450 | 400 | 500 | |
| 1915 | 450 | 400 | 500 | |
| 1920 | 450 | 400 | 500 | |
| 1925 | 450 | 400 | 500 | |
| 1930 | 450 | 400 | 500 | |
| 1935 | 450 | 400 | 500 | |
| 1940 | 450 | 400 | 500 | |
| 1945 | 450 | 400 | 500 | |
| 1950 | 450 | 400 | 500 | |
| 1955 | 450 | 400 | 500 | |
| 1960 | 450 | 400 | 500 | |
| 1965 | 450 | 400 | 500 | |
| 1970 | 307.95 | 450 | 400 | 500 |
| 1975 | 319.54 | 450 | 400 | 500 |
| 1978 | 328.31 | 450 | 400 | 500 |
| 1979 | 331.83 | 450 | 400 | 500 |
| 1980 | 335.64 | 450 | 400 | 500 |
| 1981 | 338.16 | 450 | 400 | 500 |
| 1982 | 341.23 | 450 | 400 | 500 |
| 1983 | 344.23 | 450 | 400 | 500 |
| 1984 | 347.32 | 450 | 400 | 500 |
| 1985 | 350.26 | 450 | 400 | 500 |
| 1986 | 353.39 | 450 | 400 | 500 |
| 1987 | 356.41 | 450 | 400 | 500 |
| 1988 | 360.71 | 450 | 400 | 500 |
| 1989 | 363.98 | 450 | 400 | 500 |
| 1990 | 366.41 | 450 | 400 | 500 |
| 1991 | 369.15 | 450 | 400 | 500 |
| 1992 | 370.57 | 450 | 400 | 500 |
| 1993 | 371.86 | 450 | 400 | 500 |
| 1994 | 374.17 | 450 | 400 | 500 |
| 1995 | 376.88 | 450 | 400 | 500 |
| 1996 | 379.29 | 450 | 400 | 500 |
| 1997 | 381.0 | 450 | 400 | 500 |
| 1998 | 384.29 | 450 | 400 | 500 |
| 1999 | 387.22 | 450 | 400 | 500 |
| 2000 | 388.9 | 450 | 400 | 500 |
| 2001 | 390.95 | 450 | 400 | 500 |
| 2002 | 393.4 | 450 | 400 | 500 |
| 2003 | 396.61 | 450 | 400 | 500 |
| 2004 | 398.54 | 450 | 400 | 500 |
| 2005 | 401.42 | 450 | 400 | 500 |
| 2006 | 404.04 | 450 | 400 | 500 |
| 2007 | 406.32 | 450 | 400 | 500 |
| 2008 | 409.15 | 450 | 400 | 500 |
| 2009 | 411.05 | 450 | 400 | 500 |
| 2010 | 413.9 | 450 | 400 | 500 |
| 2011 | 416.39 | 450 | 400 | 500 |