TABLE B.6 Global Mean Surface Air Temperature Anomaly and Global CO, Concentration Year Anomaly (C) CO; (ppmv) Year Anomaly ('C) CO; (ppmv) Year Anomaly ('C) CO; (ppmv) 1880 -0.11 290.7 1922 -0.09 303.8 1964 -0.25 319.2 1881 -0.13 291.2 1923 -0.16 304.1 1965 -0.15 320.0 1882 -0.01 291.7 1924 -0.11 304.5 1966 -0.07 321.1 1883 -0.04 292.1 1925 --0.15 305.0 1967 -0.02 322.0 1884 -0.42 292.6 1926 0.04 305.4 1968 -0.09 322.9 1885 -0.23 293.0 1927 -0.05 305.8 1969 0.00 324.2 -0.25 306.3 1970 1971 1886 293.3 1928 0.01 0.04 325.2 306.8 307.2 307.7 1887 -0.45 293.6 1929 -0.22 -0.10 326.1 1888 -0.23 293.8 1930 -0.03 1972 -0.05 327.2 1889 0.04 294.0 1931 0.03 1973 0.18 328.8 1890 -0.22 294.2 1932 0.04 308.2 1974 -0.06 329.7 1891 -0.55 294.3 1933 -0.11 308.6 1975 -0.02 330.7 1892 -0.40 294.5 1934 0.05 309.0 1976 -0.21 331.8 1893 -0.39 294.6 1935 -0.08 309.4 1977 0.16 333.3 1894 -0.32 294.7 1936 0.01 309.8 1978 0.07 334.6 1895 -0.32 294.8 1937 0.12 310.0 1979 0.13 336.9 1896 -0.27 294.9 1938 0.15 310.2 1980 0.27 338.7 1897 -0.15 295.0 1939 -0.02 310.3 1981 0.40 339.9 1898 -0.21 295.2 1940 0.14 310.4 1982 0.10 341.1 1899 -0.25 295.5 310,4 1983 1984 1941 0.11 0.34 342.8 1900 -0.05 295.8 1942 0.10 310.3 0.16 344.4 1901 -0.05 296.1 1943 0.06 310.2 1985 0.13 345.9 1902 -0.30 296.5 1944 0.10 310.1 1986 0.19 347.2 1903 -0.35 296.8 1945 -0.01 310.1 1987 0.35 348.9 1904 -0.42 297.2 1946 0.01 310.1 1988 0.42 351.5 A 1905 -0.25 297.6 1947 0.12 310.2 1989 0.28 352.9 Table B.16 presents data on the U.S. Gross Domestic Product (GDP). Plot the GDP data and calculate the sample autocorrelation function. Is there an indication of nonstationary behavior in the time series? Now plot the first difference of the GDP time series and compute the sample autocorrelation function of the first differences. What impact has differencing had on the time series?