Early in previous interglacial intervals, the methane concentration typically reached a peak of almost 700 parts per billion (ppb) as precession brought summer radiation to a maximum.

• 先前的间冰期早期，夏季辐射由于岁差而达到最大值时，通常甲烷浓度也到达高峰，约700ppb（ppb为十亿分之一）。