Figure 5.1. Reconstruction of: A - air-surface temperature by Greenland Ice Cores O¹⁸ for the last 1420 years (Dansgaard et al. 1975); B - summer temperature by Scots Pine Tree Rings for the last 1400 years (Briffa et al. 1990); C and D - sardine and anchovy biomass estimated from Californian varved bottom sediments for the last 1700 years (Baumgartner et al. 1992). Time series of sardine and anchovy abundance are averaged by 10-year sections. Cyclic fluctuations of climate and commercial fish stocks are believed to have a period of at least several decades.