Global Warming

The dataset GlobalWarmingData contains estimates of global annual temperature variations, relative to a 1950 through 1979 reference period, for the 138 years, 1854 through 1991. This data comes from P. D. Jones, T. M. L. Wigley, and P. B. Wright at the University of East
Anglia and can be obtained on-line at the Carbon Dioxide Information Center.

We make a least squares quadratic curve fit to the data using LinearFit. This gives us the overall trend.

WarmingDataFit = 
      LinearFit[GlobalWarmingData, {0, 1, 2}, t, 
        ReturnResiduals -> True];

We can attempt to discern structure in the residuals by fitting to a (6^th) order curve.  To supress the effects of outliers we use the RobustCurveFit function. The resulting residuals appear to be more even.

RobustCurveFit[
      ({#1[[1]], #1
                [[2, 1]]}&)/@
        (Residuals /. WarmingDataFit), {0, 1, 2, 3, 4, 5, 6}, t];