FIGURE 1. A long look back.

From the following article:

Palaeoclimate: Windows on the greenhouse

Ed Brook

Nature 453, 291-292(15 May 2008)

doi:10.1038/453291a

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a, The 800,000-year records of atmospheric carbon dioxide (red; parts per million, p.p.m.) and methane (green; parts per billion, p.p.b.) from the EPICA Dome C ice core1, 2, together with a temperature reconstruction (relative to the average of the past millennium) based on the deuterium–hydrogen ratio of the ice6, reinforce the tight coupling between greenhouse-gas concentrations and climate observed in previous, shorter records. The 100,000-year 'sawtooth' variability undergoes a change about 450,000 years ago, with the amplitude of variation, especially in the carbon dioxide and temperature records, greater since that point than it was before. Concentrations of greenhouse gases in the modern atmosphere are highly anomalous with respect to natural greenhouse-gas variations (present-day concentrations are around 380 p.p.m. for carbon dioxide and 1,800 p.p.b. for methane). b, The carbon dioxide and methane trends from the past 2,000 years13, 14.

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