According to a report by The Guardian, a new study published in Scientific Reports indicates that the current level of carbon dioxide in the Earth's atmosphere is approaching a peak not seen in 15 million years, possibly the first time this has occurred since the birth of apes.
Based on the rate of increase before the Wuhan lockdown due to COVID-19, atmospheric carbon dioxide levels will exceed 427 ppm within five years. This figure is likely the peak of warming during the mid-Pliocene epoch 3.3 million years ago, when temperatures were 3°C to 4°C higher than today and sea levels were 20 meters higher.
Around 2025, Earth may experience a carbon dioxide peak not seen since the Miocene Climatic Optimum (MCO) 15 million years ago. At that time, solar radiation levels were similar to today, and human ancestors diverged from apes to become great apes.
A research team from the University of Southampton studied tiny fossils, as small as pinheads, in deep-sea sediments in the Caribbean Sea. Using the boron content in these fossils, they constructed a high-precision record of atmospheric carbon dioxide levels during the Pliocene epoch.
The findings echo trends observed in past ice core studies, but provide a more precise estimate of carbon dioxide levels.
"We found that at the hottest point in the Pliocene, atmospheric carbon dioxide levels were between 380 and 420 ppm, which is quite close to today's level of about 415 ppm," said co-author Thomas Chalk. "This means that the last time atmospheric carbon dioxide levels were this high, temperatures and sea levels were much higher than they are today."
"Currently, atmospheric carbon dioxide levels are increasing at a rate of about 2.5 parts per million per year and by 2025 will surpass the highest level seen in the past 3.3 million years," said Chalke.
The authors stated that the study could have predicted how the Earth would react after two centuries of industrial emissions and massive accumulation of greenhouse gases.
Another author, Gavin Foster, professor of isotope geochemistry at the University of Southampton, said that Earth is transitioning from an environment similar to the Pliocene to the Miocene. The ice sheets were smaller in the middle Miocene, and sea levels were much higher than in the Pliocene. This is long before humans appeared on Earth.
The World Meteorological Organization (WMO) and the UK Met Office are conducting an international collaborative project to update climate forecasts annually for five consecutive years. At the first climate forecast presentation on the 9th, scientists pointed out that current temperatures are steadily rising, and by 2025, there is only a 20% chance that global temperatures will rise to 1.5°C above pre-industrial levels. WMO Secretary-General Petteri Taalas stated, "This study, with its advanced science and technology, demonstrates just how difficult it will be to achieve the goals of the Paris Climate Agreement—to limit warming to 2°C and, ideally, to 1.5°C."
Source: The Guardian (July 9, 2020), CO2 in Earth’s atmosphere nearing levels of 15m years ago
