TUESDAY, April 4, 2017 (HealthDay News) -- In a century or two, Earth's climate could warm to a level that last occurred hundreds of millions of years ago, some researchers predict.
After studying evidence of ancient atmospheric conditions, investigators concluded that if people burn all available fossil fuels, carbon dioxide (CO2) levels in the atmosphere would be similar to 200 million years ago.
The result: By the 23rd century, Earth's climate could be its hottest in 420 million years, the researchers warned.
CO2 levels in the atmosphere have varied over millions of years. But fossil fuel use in the last 150 years has boosted levels from 280 parts per million (ppm) before industrialization to nearly 405 ppm in 2016, according to the researchers.
If people don't halt rising CO2 levels and burn all available fossil fuels, CO2 levels could reach 2,000 ppm by the year 2250, the researchers said. CO2 and other gases act like a blanket, preventing heat from escaping into space. That's known as the greenhouse effect, the researchers explained.
The "resultant climate change [will] be faster than anything the Earth has seen for millions of years, the climate that will exist is likely to have no natural counterpart, as far as we can tell, in at least the last 420 million years," study lead author Gavin Foster said in a news release from the University of Southampton in England. He is a professor of isotope geochemistry at the university.
The researchers noted that CO2 is not the only factor in climate change. Changes in the amount of incoming light also tip the balance, and nuclear reactions in stars like the sun have made them brighter over time, according to study co-author Dan Lunt. He's a professor of climate science at the University of Bristol in England.
Though CO2 levels also were high millions of years ago, because there was less light, the net warming was less, Lunt said.
Study co-author Dana Royer, a professor of earth and environmental sciences at Wesleyan University in Middletown, Conn., said the interplay is important.
"Up to now it's been a puzzle as to why, despite the sun's output having increased slowly over time, scant evidence exists for any similar long-term warming of the climate. Our finding of little change in the net climate forcing offers an explanation for why Earth's climate has remained relatively stable, and within the bounds suitable for life all this time," Royer said in the release.
The study was published April 4 in the journal Nature Communications.
The World Health Organization the connection between climate change and health.