Mid-Piacenzian Warm Period

The Mid-Piacenzian Warm Period (mPWP), occurring from 3.3 to 3.0 million years ago, was a time of elevated global temperatures, 2–3 °C higher than today, and sea levels 25 meters above current levels. The Northern Hemisphere ice sheet was minimal before Greenland's glaciation began around 3 Ma, with reduced permafrost extent and slightly increased precipitation globally. Regional climates varied significantly: eastern Alaska experienced temperatures 7-9 °C warmer than now, while the Arctic hosted thermophilic vegetation. Spain's Camp del Ninots had a mean annual temperature of 14.3°C with substantial rainfall.

In East Asia, the winter monsoon strengthened, but the summer monsoon's reach diminished, causing drier conditions in the Chinese Loess Plateau. Southern Africa saw precipitation zones shift poleward by ∼1°, with reduced rainfall, while Ecuador's coast became drier and South Africa's vegetation transitioned to fynbos and Afrotemperate forests. The Kuroshio Current Extension moved north, and the South Asian Summer Monsoon intensified.

CO2 concentrations during this period were around 400 ppm, comparable to current levels. This makes the mPWP a relevant analogue for future climate scenarios, with similar CO2 levels and geography. Climate models indicate pronounced warming at high latitudes, up to 10–20 °C warmer above 70°N, while tropical regions saw little change. Biomes shifted northward, with tundra and taiga expanding into new areas, and savannas and warm-temperate forests growing in Africa and Australia. The period also noted intensified tropical cyclones, suggesting potential future storm intensification under global warming.