500 Million Years of Climate History Tells Us of a Coming Catastrophe

The climate is warming, that is a fact. But what will be the consequences in the short, medium or even long term? Predicting the future is always risky, especially when we do not have full control over all climatic processes and interconnections with other terrestrial domains (hydrosphere, geosphere, biosphere). Despite everything, studying the past, and especially climate changes throughout Earth’s history, can help us predict the changes we will have to face in the coming decades and centuries.

Global temperature curve over the past 485 million years

Glacial (recent) and geological (distant) archives already contain many small clues that make it possible to reconstruct ancient climates. Thus, the researchers were able to find the evolution of the average surface temperature of the Earth over the past 485 million years. This result was published in the journal sciencesresulting from the assimilation of a large number of data from geological studies and climate models. The goal was actually to obtain a complete and coherent view of temperature evolution, even when the field data were fragmented. However, the further back in time we go, the more scarce the data become.

To have a chance to understand exactly how climate will evolve in the future, compared to today, researchers cannot limit themselves to a few million years ago. In fact, a broad view is required.

The main role of carbon dioxide in climate

So the scientists decided to monitor the entire (or almost) Phanerozoic Eon, which began 540 million years ago, when the first animals appeared. The new findings also reveal that temperatures varied much more than previously thought during this period. The average surface temperature of the Earth could therefore have fluctuated between two extremes: 11 and 36 degrees Celsius. For comparison, today’s temperature is 15 degrees Celsius. The Phanerozoic Eon therefore recorded temperatures much higher than those we know today, especially during the Paleocene-Eocene Thermal Maximum 56 million years ago. These fluctuations appear to be closely linked to the rate of carbon dioxide.₂ In the atmosphere.

Thus, this new study supports the idea that carbon dioxidecarbon dioxide It is the dominant factor controlling the evolution of global temperature. When the rate of carbon dioxide₂ Low, the climate is cold. When it is high, the temperatures rise. It may seem strange to remember this, but the relationship between CO₂ Temperature is not so clear when looking at a short time scale. Moreover, climate skeptics often use this angle to downplay the role of humans on the planet. Global warmingGlobal warming present.

Thanks to the long time period observed, this study aims to be authoritative on the major role played by carbon dioxide.₂ The atmosphere on the Earth's climate and thus on human questions in the current climate crisis. Another point highlighted by this study is speedspeed An unprecedented level of global warming and the risks that these rapid disruptions will bring to everyone EcosystemsEcosystems.

A change so brutal that it does not allow ecosystems to adapt.

Scientists point out that the current average surface temperature is located at the bottom of the Earth. rangerange The temperature recorded during the Phanerozoic. In other words, we are in a fairly cool period if we look at the past 500 million years. But that is not the point. It is the speed of change. Because, as paleoclimatologist Jessica Tierney pointed out in a press release, “ Men and others ClassClass Those we share this planet with are adapted to cold climates. Putting ourselves too quickly in a hot climate is dangerous. “

Of the climate fluctuations in the past, some occurred very slowly, in which case species had time to adapt, while others occurred very suddenly. However, the latter are often associated with mass extinctions. The speed of current change therefore makes the risk of such a scenario recurring possible.