interglacials

An interglacial is a warm interval within a longer ice-age climate, during which the planet's ice sheets retreat, global temperatures rise, and sea levels climb. Interglacials stand in contrast to glacial periods, when ice sheets are extensive and global temperatures are cooler. Interglacials are part of the recurring Quaternary glaciation cycle and are typically identified by higher atmospheric greenhouse gas concentrations than during glacial maxima.

Most interglacials are linked to variations in Earth's orbit (Milankovitch cycles) that change the distribution and intensity of sunlight received at the surface, particularly in high latitudes. These orbital shifts trigger warming, which can be amplified by feedbacks such as reduced ice-albedo, increased water and soil moisture, and rising greenhouse gas levels.

Durations vary; interglacials generally last on the order of several tens of thousands of years. The current interglacial is the Holocene, beginning about 11,700 years ago, with ongoing warmth and rising human influence. The previous interglacial, the Eemian (around 130,000 to 115,000 years ago), featured similar but somewhat warmer conditions in parts of the world.

Paleoclimate records from ice cores, marine sediments, and other archives are used to study interglacials and to estimate past temperatures, greenhouse gas levels, and sea level. Understanding interglacials helps contextualize present-day climate change within natural variability and long-term climate trends.