According to the website of the German newspaper Suddeutsche Zeitung, the global average temperature is heading towards a rise of more than 3 degrees Celsius. Kasia Silivinska, a geologist at the Geological Survey of Denmark and Greenland, said that although such hot weather has occurred many times in history, people should not take it lightly.
A reporter from the Suddeutsche Zeitung asked: You have studied the Miocene, a geological period millions of years ago. What makes this geological period so interesting today?
Kasia Silivinska replied: The Miocene - the period from about 23 million years ago to 5.3 million years ago - is interesting because it can be used as a reference interval for predicting future climate. In the early Miocene, the concentration of carbon dioxide in the global atmosphere was similar to that of the pre-industrial period, about 300 ppm (1 ppm is one part per million). Then, from 17 million years ago to 15 million years ago, the concentration of carbon dioxide rose to more than 420 ppm, leading to a warming period that lasted about 2 million years, which is the Miocene climate suitable period. This was the last time in history that atmospheric CO2 concentrations were as high as they are today. So we can look back to the Miocene Optimum and use it as a reference period for future climate predictions. It's like time travel.
Q: From your research, it seems that this period was actually quite comfortable: warm and humid, rich in species. Was it a paradise for plants and animals?
A: It might have been. The data show that during the Miocene Optimum, the average world temperature was 3 to 5 degrees Celsius higher than in pre-industrial times, and the air was much wetter. But the reality of our daily lives in northern central Europe in the future due to climate change doesn't sound nearly as pleasant. People like to go on vacation to places like that. But living at 28 degrees Celsius for a long time can be quite exhausting and even harmful to your health.
Q: Climate change deniers often say that the Earth was warmer in the past, and that it was either getting colder or warmer. How do you answer this question?
A: Yes, the climate has always changed in the past, and at some stages it was warmer than it is now. But first of all, it should be noted that CO2 concentrations have never increased as fast as they are now. In other words, we have really disrupted the natural rhythm of climate change. In addition, every time the climate warmed in the past, the air also became more humid.
When there were no humans on Earth, this change might have been peaceful, but today it is completely different. Just last fall and winter here in Denmark, it rained so hard that it was difficult for farmers to get their machinery to the fields to plant. Even in Europe, floods are becoming more common. And our entire food production and infrastructure depend on a stable climate. We may still face several tipping points in the global climate due to the sharp increase in carbon dioxide concentrations in the atmosphere. Greenhouse gas emissions are not decreasing significantly year by year, making it more difficult to stop the warming.
Q: People worry that once the tipping point is crossed, the warming trend cannot be reversed. But doesn't your research show that the Earth can find balance again?
A: Yes, but we are talking about long periods of time here. During the Miocene Optimum, we don't see any mass extinction events of plants and animals because everything happened slowly. Since there was no infrastructure or settlements at the time, it was easy for plants and animals to migrate to colder areas. But when the changes happen quickly like today, they will have a hard time adapting. And this is not only about how the Earth will cope with climate change, but also about what climate change means for us humans.
Q: Where did the increased carbon dioxide come from? After all, there were no factories burning coal or natural gas.
A: According to the leading hypothesis, volcanic activity was very active for a long time. Evidence of this volcanic activity can be found near what is now Washington, D.C. in North America. Other studies have suggested that ocean currents flowed differently than they do now, so the heat was distributed differently around the globe. In any case, these changes occurred much more slowly than the changes we see today.
Q: If humans continue to emit so many greenhouse gases, will we end up returning to a world like the Miocene in the long run?
A: One has to distinguish between different scenarios. In the more optimistic future, the average global temperature may be 2 degrees Celsius higher than in the pre-industrial period. Then our climate would be similar to the mid-Pliocene, about 3 million years ago.
Q: What if greenhouse gases continue to increase?
A: This is a very negative scenario and it may not happen. But if we continue to emit at this rate, atmospheric CO2 concentrations will rise to levels not seen since the so-called Early Eocene Optimum, between 54 and 49 million years ago. Back then, the climate was so warm that there were palm trees in Antarctica and crocodiles in the high north. In general, it was very hot and humid. It's hard to imagine how humans could have survived under those conditions.
