Figure 2.7: Smoothed annual
anomalies of combined land-surface air and sea surface temperatures (°C),
1861 to 2000, relative to 1961 to 1990, for (a) Northern Hemisphere; (b) Southern
Hemisphere; and (c) Globe. The smoothed curves were created using a 21-point binomial
filter giving near-decadal averages. Optimally averaged anomalies (Folland et
al., 2001) � solid curves; standard area weighted anomalies (adapted from
Jones et al., 2001) � dashed curves. Also shown are the unsmoothed optimum
averages � red bars, and twice their standard errors � width denoted
by black �I�. Note that optimum averages for the Southern Hemisphere
are a little warmer before 1940, when the data are sparse, than the area-weighted
averages. However, the two types of averaging give similar resoults in the Northern
Hemisphere.
