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"The year by year (blue curve) and
50 year average (black curve) variations of the average surface temperature
of the Northern Hemisphere for the past 1000 years have been reconstructed from
“proxy” data calibrated against thermometer data (see list of the
main proxy data in the diagram).
The 95% confidence range in the annual
data is represented by the grey region. These uncertainties increase in more
distant times and are always much larger than in the instrumental record due
to the use of relatively sparse proxy data. Nevertheless the rate and duration
of warming of the 20th century has been much greater than in any of the previous
nine centuries. Similarly, it is likely7
that the 1990s have been the warmest decade and 1998 the warmest year of the
millennium.
Based
upon Chapter 2, Figure 2.20"
Source
& © : IPCC
TAR SPM of WG I
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