![Five graphs, arranged in rows, showing Milankovitch cycles, incoming sunlight, and global ice volume over the past million years](/sites/default/files/2021-08/orbital_cycles_sunlight_ice_lrg.jpg)
Image caption
(Rows 1-3) Milankovitch cycles over the past million years (tilt, precession, and eccentricity. (Row 4) Northern Hemisphere summer insolation. (Row 5) Global ice volume inferred from oxygen isotopes in sea floor sediments. Light gray column highlights conditions around 220,000 years ago, when overlap among the three orbital cycles brought a peak in Northern Hemisphere insolation, triggering a warming period with low ice sheet volume. NOAA Climate.gov image, based on data from Lisiecki and Raymo, 2005.