The NOAA land-ocean temperature anomaly for the years 1970 through 2007 shows a fairly linear global warming trend with a slope of 0.0173°C per year. The standard deviation of the anomaly from the trend line in this interval of time is σ = 0.1210. So far the anomaly has remained within the 3σ bounds for the fluctuations of the anomaly but the more recent anomalies appear to be dropping below the trend line. One has to ask if the warming trend will continue?
The trend can be treated as a theory of global warming that can be subjected to statistical testing. If the anomaly shows a large number of months outside the bounds for the trend then we have to reject this theory of global warming. We would also have to ask if enough has been done in terms of reducing greenhouse gases to explain an observed reduction in the global warming trend. The next few years may help us decide if what we have been hearing is true science of mere speculation.
Correction (Mar 4): The value of a = 0.1408 above is for the reference year 1980. From the plot one can see that Trend for 1970 is slightly less than 0. The correct value with 1970 for the reference year is a = -0.0328.
