"year"  "ppm/yr"
1959   0.94
1960   0.54
1961   0.95
1962   0.64
1963   0.71
1964   0.28
1965   1.02
1966   1.24
1967   0.74
1968   1.03
1969   1.31
1970   1.06
1971   0.85
1972   1.69
1973   1.22
1974   0.78
1975   1.13
1976   0.84
1977   2.10
1978   1.30
1979   1.75
1980   1.73
1981   1.43
1982   0.96
1983   2.13
1984   1.36
1985   1.25
1986   1.48
1987   2.29
1988   2.13
1989   1.32
1990   1.19
1991   0.99
1992   0.48
1993   1.40
1994   1.91
1995   1.99
1996   1.25
1997   1.91
1998   2.93
1999   0.93
2000   1.62
2001   1.58
2002   2.53
2003   2.29
2004   1.56
2005   2.52
2006   1.76
2007   2.22
2008   1.59
2009   1.89
2010   2.42
2011   1.88