Figure 2.19: Reconstructed
global ground temperature estimate from borehole data over the past five centuries,
relative to present day. Shaded areas represent ± two standard errors about
the mean history (Pollack et al., 1998). Superimposed is a smoothed (five-year
running average) of the global surface air temperature instrumental record since
1860 (Jones and Briffa, 1992).
