The Pliocene sounds like a holiday: in the epoch of the earth's history, just over 5.3 to 2.5 million years ago, global temperatures were three to four degrees higher than today. Giraffes lived in Europe, plants grew in the Antarctic and Greenland was completely ice-free. However, the sea level was 15 to 20 meters higher than today. Researchers have long been interested in this period. The Pliocene is also traded as a blueprint for the future climate because there was as much carbon dioxide in the atmosphere at that time as it does today.
Now, analyzes of the Potsdam Institute for Climate Impact Research (PIK) suggest that the current level of CO2 in the Earth's atmosphere is indeed currently at a higher level than ever before in the past three million years. The research results are based on computer simulations based on geological and astronomical data.
Using simulations, the scientists used different scenarios, which they compared with data from seabed sediments, which provide information about the prevailing climatic conditions, they write in the journal Science Advances. "The fact that the model can reproduce the main features of the observed climate history makes us confident that we have understood the basic functions of the climate system," said Pik researcher Andrey Ganopolski.
"As fascinating as that is, it is also worrying"
According to the simulations, slight changes in the Earth's orbit and the lower carbon dioxide content of the atmosphere caused the Pliocene to come to an end and the Pleistocene followed with a change in warm and cold periods.
"Our results indicate a high sensitivity of the Earth system to relatively small variations in atmospheric CO2," said Matteo Willeit, lead author of the study. "As fascinating as that is, it is also worrying."
According to the researchers, global temperature has never risen by more than two degrees Celsius over the past three million years, compared to the pre-industrial era. At the moment, the temperatures are about one degree Celsius above. However, without comprehensive climate protection measures, the temperature could rise by two degrees within the next 50 years, the researchers warn.
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The goal of no more than two degrees of average global warming is considered a limit to prevent serious consequences for humans and the environment. If possible, global warming should, according to the Paris Agreement, be limited to just 1.5 degrees.
However, according to researchers, this target can only be achieved if emissions fall by 45 percent compared to 2010 - and by 2050 at the latest, total carbon dioxide emissions must be brought to zero. (Here you can read more about it).
If, on the other hand, it remains with the current commitments of the states for the Paris climate agreement, global temperatures could rise in the coming decades on average by 2.6 degrees Celsius to 4 degrees Celsius. In terms of temperatures, the world would have arrived back in the Pliocene.