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CO2 levels ‘set to exceed warmest point in three million years’ by 2025

By Ben Mitchell, PA

Atmospheric carbon dioxide (CO2) levels are set to be higher by 2025 than they were during the warmest period of the last 3.3 million years, according to new research.

Scientists from the University of Southampton have studied the chemical composition of tiny fossils about the size of a pin head from the Caribbean seabed to reconstruct the concentration of CO2 in the Earth’s atmosphere three million years ago.

The planet was more than three degrees celsius warmer than today during the Pliocene Epoch, with smaller polar ice caps and higher global sea-levels.

Co-author of the study published in Nature Scientific Reports Dr Thomas Chalk said: “Focusing on a past warm interval when the incoming insolation from the Sun was the same as today gives us a way to study how Earth responds to CO2 forcing.

“A striking result we’ve found is that the warmest part of the Pliocene had between 380 and 420 parts per million CO2 in the atmosphere.

“This is similar to today’s value of around 415 parts per million, showing that we are already at levels that in the past were associated with temperature and sea-level significantly higher than today.

“Currently, our CO2 levels are rising at about 2.5 ppm per year, meaning that by 2025 we will have exceeded anything seen in the last 3.3 million years.”

Professor Gavin Foster, who was also involved in the study, added: “The reason we don’t see Pliocene-like temperatures and sea-levels yet today is because it takes a while for Earth’s climate to fully equilibrate to higher CO2 levels and, because of human emissions, CO2 levels are still climbing.

“Our results give us an idea of what is likely in store once the system has reached equilibrium.”