Turns climate models upside down

The atmosphere at the time of the first forests contained much less carbon dioxide than previously thought. This has major implications for what the climate was like in the days before reptiles and dinosaurs dominated our planet.

A new Danish-British study has upended our understanding of the climate 400 million years ago, the amount of carbon dioxide in the atmosphere and the impact of Earth’s first forests. Land plants seem to have had a much greater influence on climate than previously assumed. Until now, scientists believed that there was a lot of carbon dioxide in the atmosphere in the early Devonian period about 400 million years ago, and that with the appearance of the first trees and forests, the level of carbon dioxide decreased dramatically. At the same time, the Earth’s climate had cooled considerably. But this all turned out to be wrong.

New old climate model
“in a studying We explain how we came up with accurate estimates of carbon dioxide levels and how we used this data to develop a paleoclimate model. The results show that the average temperature and temperature distribution of the early and middle Devonian (410 to 380 million years ago) are comparable to today’s averages,” says Professor Barry Lomax from University of Nottingham against Saintias.

Research on fossils of terrestrial plants and similar modern plants shows that climatic conditions and carbon dioxide concentrations were very different from what was previously thought. This means that we have to look differently at the impact of land plants and trees on climate.

Arboreal time and tetrapods
Lomax explains: “In the period we are focusing on, tetrapods did not walk the earth, like reptiles or dinosaurs. There were only arthropods related to modern millipedes, centipedes and spiders. So plants are more interesting for our research. We were able to draw our conclusions from Carbon dating of fossils and analysis of stomata (stomata) on the surface of terrestrial plants”.

About 385 million years ago, the land on Earth began to grow overgrown with tall trees and forests. Prior to that time, there were only shallow-rooted green shrub plants that had no flowers. The land was dotted with these terrestrial plants. We’ve always learned that the atmosphere back then had much more carbon dioxide than it does today and that the climate was much warmer and wetter because of the extreme greenhouse effect. Only after the trees emerge will the carbon dioxide level drop, resulting in a cooler, icy-arctic climate. This hypothesis turned out to be incorrect. The search results came as a big surprise to us. I don’t think anyone on the team thought the carbon dioxide concentration in the Devonian period would be so low.”

Stomata tells the story
To estimate the amount of carbon dioxide in the atmosphere from 410 to 380 million years ago, we used a new technique. The new method allows accurate estimates of ancient carbon dioxide, based on the plant’s fixed isotopic composition. From this we can gain information about the function, size and numbers of stomata (stomata) in land plants,” Lomax explains.

The study builds on the pioneering work done by Professor Ian Woodward of University of Sheffield Who discovered that there is a negative relationship between the number of stomata on the leaf surface and the concentration of carbon dioxide in the atmosphere. “This allows us to use plant fossils as ‘memory stores’ for climatic conditions in past times and makes it possible to learn what concentrations of carbon dioxide were present hundreds of millions of years ago on Earth,” says Lomax.

Fluctuations in carbon dioxide levels
Climate scientists agree that carbon dioxide plays an important role in the development of Earth’s climate, both now and in the past. Therefore, understanding the variables that cause fluctuations in atmospheric carbon dioxide levels over the years is a major challenge for Earth scientists. New technology allows for more and more accurate research, while minimizing damage to fossil resources. “The samples we’ve been working on are rare and expensive. The process of isotope analysis is destructive, and you can only use a sample once. Technological advances have now enabled us to use very small amounts of plant material to make our measurements,” concludes Lomax.