Year	TwinBirths/1000	Year since 1980	Years up to 2009	CO2(ppm)
1980	18.92	0	1	337.80
1981	19.21	1	1	339.36
1982	19.46	2	1	340.92
1983	19.86	3	1	341.64
1984	19.88	4	1	344.05
1985	20.5	5	1	345.25
1986	21.3	6	1	346.54
1987	21.36	7	1	348.38
1988	21.8	8	1	350.38
1989	22.41	9	1	352.89
1990	22.46	10	1	353.79
1991	23.05	11	1	354.87
1992	23.35	12	1	356.17
1993	23.88	13	1	356.86
1994	24.39	14	1	358.22
1995	24.86	15	1	359.87
1996	25.84	16	1	362.04
1997	26.83	17	1	363.04
1998	28.08	18	1	365.18
1999	28.87	19	1	368.12
2000	29.3	20	1	369.25
2001	30.12	21	1	370.52
2002	31.11	22	1	372.45
2003	31.46	23	1	374.87
2004	32.15	24	1	377.00
2005	32.17	25	1	378.47
2006	32.11	26	1	381.35
2007	32.19	27	1	382.93
2008	32.62	28	1	385.44
2009	33.22	29	1	386.94
2010	33.15	30	0	388.50
2011	33.2	31	0	391.25
2012	33.15	32	0	393.12
2013	33.7	33	0	395.54
2014	33.9	34	0	397.81