ure 2-3: The Earth's surface
temperature has increased by about 0.6 o C over the record of direct temperature
measurements (1860-2000, top panel) -- a rise that is unprecedented, at
least based on proxy temperature data for the Northern Hemisphere, over the last
millennium (bottom panel). In the top panel the global mean surfac temperature
is shown year-by-year (red bars with very likely ranges as thin black whiskers)
and approximately decade-by-decade (continuous red line). Analyses take into account
data gaps, random instrumental errors and uncertainties, uncertainties in bias
corrections in the ocean surface temperature data, and also in adjustments for
urbanization over the land. The lower panel merges proxy data (year-by-year blue
line with very likely ranges as grey band, 50-year-average purple line) and the
direct temperature measurements (red line) for the Northern Hemisphere. The proxy
data consist of tree rings, corals, ice cores, and historical records that have
been calibrated against thermometer data. Insufficient data are available to assess
such changes in the Southern Hemisphere.
