510 million years old shells of marine animals have provided us some astonishing insights about the climate of Earth during those times.

Climate change is one of the most debated topics of the scientific world these days. The consequences we may have to face as a species are too severe to ignore and a lot of efforts are being made internationally to counter this horrific challenge. As the world worries about the climatic changes in today’s world, scientists have discovered some details about the climate of our planet half a billion years ago. The University of Leicester led the team of international researchers that investigated the Earth’s climate.

Their study combined fossil data with climate models to estimate the temperature of oceans in those days. They published their work in the journal ‘Science Advances’ and told the world that the animals of that time lived in a greenhouse world. According to their findings, the climatic conditions during those times were quite similar to the ones observed by the dinosaurs.

This interval in time is commonly known as the Cambrian Explosion. Scientists have believed for long that Earth had no permanent polar ice, due to greenhouse climate, in that part of its history. Despite their beliefs, they had no scientific evidence to support their claims as the details were missing. That was the time when representatives of almost all major animal groups appeared in the fossil records for the first time. This list of animals included those with shells and scientists have used these shells for this experiment. Dr. Tom Harvey of the University of Leicester explained the reason for that in the following words:

“Many marine animals incorporate chemical traces of seawater into their shells as they grow. That chemical signature is often lost over geological time, so it’s remarkable that we can identify it in such ancient fossils.”

1 mm long fossil shells were extracted from blocks of limestone in Shropshire. Their chemical analysis was done to come up with these revelations. Thomas Hearing, a Ph.D. student from the School of Geography, Geology, and the Environment at the University of Leicester, explained the process by saying,

“We then used acid to extract fossils about 1mm long from blocks of limestone from Shropshire, UK, dated to between 515 — 510 million years old. Careful examination of these tiny fossils revealed that some of them have exceptionally well-preserved shell chemistry which has not changed since they grew on the Cambrian sea floor.”

He also described the difficulties the scientists had to face and the techniques they adopted for measuring the climate of that time. He mentioned that direct measurement was obviously not possible so they looked for alternate options. As a result, they used proxy data for estimating quantities. Proxy data refers to a class of measurable quantities that respond in a predictable way to changing climate variables like temperature. He told the world that the paleo-thermometer they used for this experiment was oxygen isotope ratios. The analysis of these isotopes pointed out that the temperature of high altitude seas was quite warm. The temperature of a sea at approximately 65^o S was around 20 to 25 ^o C.

The team of researchers was keen to give it their best so they checked the feasibility of the sea temperatures by running climate model simulations for the Early Cambrian period before arriving at any conclusion. These simulations strengthened their beliefs as they also suggested that the climate of our planet was resembling greenhouse effect during that part of the history. The temperatures were quite similar to the ones that were observed in the late Mesozoic and early Cenozoic eras.

As scientists have a better understanding of these greenhouse intervals, they concluded that Earth did face greenhouse climatic conditions in the Cambrian period. They are hopeful that these findings will help humanity to know more about the early animals of that time. Similarly, it will help us to expand our knowledge about the surrounding environment in which they lived. About that, Hearing said,

“We hope that this approach can be used by other researchers to build up a clearer picture of ancient climates where conventional climate proxy data are not available.”