Millennial-scale climate instability during the early Pleistocene epoch

Climate-proxy records of the past 100,000 years show that the Earth's climate has varied significantly and continuously on timescales as short as a few thousand years (1–7). Similar variability has also recently been observed for the interval 340–500 thousand years ago8. These dramatic climate shifts, expressed most strongly in the North Atlantic region, may be linked to — and possibly amplified by — alterations in the mode of ocean thermohaline circulation4,5,6,7,8,9. Here we use sediment records of past iceberg discharge and deep-water chemistry to show that such millennial-scale oscillations in climate occurred over one million years ago. This was a time of significantly different climate boundary conditions; not only was the early Pleistocene epoch generally warmer, but global climate variations were governed largely by changes in Earth's orbital obliguity. Our results suggest that such millennial-scale climate instability may be a pervasive and long-term characteristic of Earth's climate, rather than just a feature of the strong glacial–interglacial cycles of the past 800,000 years.