A South American hockey stick Posted on 18 September 2010 by
John Cook A new paper has just been published employing a new
technique for reconstructing past temperatures (Kellerhals
2010). It uses Ammonium concentration from an ice core in
tropical South America (the eastern Bolivian Andes) as a proxy
for temperature. This enables them to build a temperature record
going back 1600 years in a region which has had little proxy
data available until now. They find a distinguishable Medieval
Warm Period and Little Ice Age in the record. Nevertheless, they
also find the last few decades show unprecedented warmth over
the last 1600 years. Figure 1: Reconstructed tropical South
American temperature anomalies (normalized to the 1961–1990AD
average) for the last 1600 years (red curve, smoothed with a
39‐year Gaussian filter). The shaded region envelops the ±2
standard deviation uncertainty as derived from the validation
period. Poor core quality precluded any chemical analysis for
the time interval between 1580 and 164