Introduction: A long-standing climate puzzle For millions of years, the Earth’s climate oscillated between frigid glacial periods and warmer interglacials. Among these, the so-called lukewarm interglacials, spanning roughly from 800,000 to 430,000 years ago, are particularly intriguing. During these warmer phases, atmospheric CO2 hovered around 240–260 ppm, with later interglacials reaching 280–300 ppm. Today, CO2…