One way to make more accurate forecasts of global warming over the coming centuries is to look at climate change in the geological past. In a study published in Nature Communications, an international team of university experts from Germany, the United States, and the United Kingdom studied the climate during the Eocene era – more than 30 million years ago. Then the average temperature on the planet was higher than today. Scientists have found that the effect of atmospheric carbon dioxide on a warm Earth maybe even stronger than previously thought.
The Eocene epoch began between 56 and 34 million years ago – the last greenhouse period in Earth’s history associated with global warming. Back then, temperate rainforests could be found in Antarctica, and crocodiles took over the wet swamps that covered North America and parts of Europe. However, during the Eocene, the climate became sharply colder, and the era ended with a major transition to the climate we are seeing now, with the glaciation of Antarctica.
Until now, it was unclear how climate change and CO2 are related during this period. Recent climate model studies have shown that warmer climates are more sensitive to changes in carbon dioxide than colder ones. This may be of particular importance for our future, as the amount of CO2 only increases, and the Earth continues to heat up.
Based on the acidity of surface waters (pH) and estimates of the state of ocean saturation with calcite, the authors calculated how atmospheric CO2 was released during the Eocene. The data used were obtained in the study of the boron isotopic composition of fossil shells of ancient marine plankton deposited on the seabed in the Eocene. It was collected on expeditions to the International Ocean Science Program.
New CO 2 data provide a new and comprehensive insight into the evolution of climate in the Eocene and provide compelling evidence for the relationship between CO 2 levels and warm climates. It shows how volcanism, weathering of rocks, and the disposal of organic material affect the natural concentration of CO 2 and therefore the climate.
Now that we have demonstrated that the climate is more sensitive when it is warm, as it was during the Eocene, the next step is to find out why this is so and to ensure that such a relationship is represented in the climate models that are used to predict future climate.
Dr. Tali Babila, Research Fellow at the University of Southampton and co-author of the study