The exhibition presents evidence of the great climate changes that have occurred over the last 65 million years. Fossils found around the world indicate that between 58 million years ago (late Paleocene) and 50 million years ago (early Eocene), the temperature of the ocean and atmosphere was much higher than it is today. The culmination of this warm period occurred around 55 million years ago. In just a few thousand years, the average temperature of the deep ocean rose by 4 - 5°C, the temperature of the ocean surface waters in higher latitudes rose by as much as about 8°C and in tropical latitudes by about 5°C. This period is referred to as the Paleocene-Eocene Thermal Maximum (PETM-Paleocene/Eocene Thermal Maximum). The PETM lasted about 170,000 years. These and many other extremely interesting pieces of information are contained in the charts in the exhibition.

Valuable additions to the knowledge on the charts are plant fossils from the Earth Museum's collection as evidence of the Great Warming. Among those presented are specimens from Europe, leaf imprints and wood fragments from Middle Eocene sites in the Geisel river valley (Geiseltal, Germany), fossilised Nypa palm fruit from Middle Eocene sediments from Schaarbreek (Brussels district; Belgium). Also shown are very interesting fossils from Poland - leaf imprints of evergreen plants from the Eocene site at Chłabówka (Podhale). The fossils we present, as well as a number of others known from Europe, unquestionably indicate that almost the entire area of Europe was dominated by evergreen, almost tropical vegetation. The average annual temperature here may have been as high as around 20°C!

Tree leaf prints from polar areas, from the Palaeogene sediments of Spitsbergen and Antarctica, are an extremely suggestive addition. The tree remains found in polar areas perfectly show how much and global warming we faced in the early Palaeogene.