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HadCRUT3 Diagnostics: global average (NH+SH)/2

Calculating the global mean as the mean of the northern and southern hemisphere averages helps prevent the value becoming dominated by the Northern hemisphere, where there are more observations.

We have recently changed the way that the smoothed time series of data were calculated. Data for 2008 were being used in the smoothing process as if they represented an accurate esimate of the year as a whole. This is not the case and owing to the unusually cool global average temperature in January 2008, it looked as though smoothed global average temperatures had dropped markedly in recent years, which is misleading.

Annual series

The red bars show the global annual average near surface temperature anomalies from 1850 to 2007. The error bars show the 95% uncertainty range on the annual averages. The green bar shows the provisional average for the present year. The thick blue line shows the annual values after smoothing with a 21 point binomial filter. The thin blue lines show the 95% uncertainty on the smoothed curve.

Annual series smoothed with a 21-point binomial filter

Data file (in this format).

Annual series

Data file (in this format).

Monthly series

Data file (in this format).

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