A team of Earth scientists has made a groundbreaking discovery about a crucial step in the Earth’s climate development. Approximately 700,000 years ago, the planet experienced a “warm ice age” that had lasting effects on its climate cycles. This period of intense heat and humidity coincided with the expansion of polar glaciers, marking a significant shift in the Earth’s weather patterns.
The research team, comprised of European scientists including geoscientists from Heidelberg University, used newly obtained geological data and computer models to understand the relationship between the warm ice age and changes in climate cycles. Their findings suggest that this pivotal shift in weather patterns played a vital role in shaping the subsequent climate history of our planet.
Geological ice ages, known as glacial periods, are characterized by the development of large ice sheets in the Northern Hemisphere. Over the past 700,000 years, the Earth has experienced alternating glacial and warm periods roughly every 100,000 years. However, prior to this period, the climate followed 40,000-year cycles with shorter and milder glacial periods. The transition from 40,000-year cycles to the current 100,000-year cycles occurred during the Middle Pleistocene Transition period, which occurred from around 1.2 million years ago to approximately 670,000 years ago.
Associate Professor Dr. André Bahr of the Institute of Earth Sciences at Heidelberg University explains, “The mechanisms behind this critical change in the global climate rhythm remain largely unknown, and they cannot be attributed to variations in the orbital parameters governing the Earth’s climate. However, the recently identified ‘warm ice age,’ which led to the accumulation of additional continental ice, played a critical role.”
To study this phenomenon, the researchers analyzed climate records from a drill core off Portugal and loess records from the Chinese Plateau. They then used computer simulations to model long-term warming and wetting trends in subtropical regions over the past 800,000 to 670,000 years. During the Middle Pleistocene Transition period, sea surface temperatures in the North Atlantic and tropical North Pacific were warmer than in the interglacial period preceding the last ice age.
These higher temperatures led to increased moisture production and rainfall in Southwest Europe, the expansion of Mediterranean forests, and an enhanced summer monsoon in East Asia. The moisture also reached the polar regions, contributing to the expansion of the Northern Eurasian ice sheets.
“André Bahr states, “This expansion of continental glaciers persisted for some time and marked the beginning of sustained and extensive ice-age glaciation that lasted until the late Pleistocene. This expansion was necessary to trigger the shift from 40,000-year cycles to the 100,000-year cycles we experience today, which was crucial for the Earth’s later climate evolution.”
The research, titled “Moist and warm conditions in Eurasia during the last glacial of the Middle Pleistocene Transition,” was published in Nature Communications. The study involved scientists from Germany, France, Spain, and Portugal and was funded by the German Research Foundation. This discovery provides valuable insights into the Earth’s climate history and will contribute to future studies on climate change and its implications.