The Bølling–Allerød interstadial (), also called the Late Glacial Interstadial, was an abrupt warm and moist interstadial period that occurred during the final stages of the Last Glacial Period. This warm period ran from 14,690 to 12,890 years before the present (BP). It began with the end of the cold period known as the Oldest Dryas, and ended abruptly with the onset of the Younger Dryas, a cold period that reduced temperatures back to near-glacial levels within a decade. In some regions, a cold period known as the Older Dryas can be detected in the middle of the Bølling–Allerød interstadial. In these regions the period is divided into the Bølling oscillation, which peaked around 14,500 BP, and the Allerød oscillation, which peaked closer to 13,000 BP. Estimates of rise are 20–35 ppmv within 200 years, a rate less than 29–50% compared to the anthropogenic global warming signal from the past 50 years, and with a radiative forcing of 0.59–0.75 W m−2. A previously unidentified contributor to atmospheric was the expansion of Antarctic Intermediate Water, which is poor at sequestering the gas. History In 1901, Danish geologists Nikolaj Hartz (1867–1937) and Vilhelm Milthers (1865–1962) provided evidence for climatic warming during the last glacial period, sourced from a clay-pit near Allerød (Denmark). Effects It has been postulated that teleconnections, oceanic and atmospheric processes, on different timescales, connect both hemispheres during abrupt climate change. The Meltwater pulse 1A event coincides with or closely follows the abrupt onset of the Bølling–Allerød (BA), when global sea level rose about 16 m during this event at rates of 26–53 mm/yr. Records obtained from the Gulf of Alaska show abrupt sea-surface warming of about 3 °C (in less than 90 years), matching ice-core records that register this transition as occurring within decades. Scientists from the Center for Arctic Gas Hydrate (CAGE), Environment and Climate at the University of Tromsø, published a study in June 2017, describing over a hundred ocean sediment craters, some 3,000 meters wide and up to 300 meters deep, formed due to explosive eruptions, attributed to destabilizing methane hydrates, following ice-sheet retreat during the last glacial period, around 12,000 years ago, a few centuries after the Bølling–Allerød warming. These areas around the Barents Sea still seep methane today, and still-existing bulges with methane reservoirs could eventually have the same fate. Ice-sheet retreat Isostatic rebound in response to glacier retreat (unloading), increase in local salinity