July-August, Volume 87, No. 4

Figure 6. Ice-core record from Vostok, Antarctica provides a record of climate change over the past 500,000 years. Shown at top is the deuterium record (a proxy for temperature) for the past 160,000 years, which contains the last glacial-interglacial cycle. The climate transitions are not as abrupt in central portions of Antarctica as they are in more coastal locations. The atmospheric CO₂ record clearly shows how human activity has increased both the concentration of CO₂ and the rate of increase of CO₂ to unprecedented levels. (Deuterium data from J. Jouzel, Laboratoire de Modélisation du Climat et de l’Environnement, France. CO₂ data, from direct observations and three different ice cores, come from C. Keeling, Scripp’s Institution of Oceanography; A. Indermuhle and A. Neftal, University of Bern; and J. Barnola et al., Laboratoire de Glaciologie et Géophysique de l’ Environnement, France.)