LOS ANGELES - The ratio of carbon dioxide in Earth's atmosphere is flirting with 400 parts per million, a level last seen about 2.5 million to 5 million years ago, according to the Scripps Institution of Oceanography at the University of California at San Diego.
The institution this week launched a daily Keeling curve update, showing the saw-toothed upward diagonal of rising carbon dioxide levels since the late 1950s.
Isolated measurements have peaked at above 400 parts per million in the Arctic, but scientists are more alarmed at steady readings from Mauna Loa, Hawaii, far from major pollution sources. Those measurements, considered to be the most reliable indicators of Earth's atmospheric content, could breach the 400 level this month, Scripps said.
The speed at which Earth's atmosphere has reached that density of carbon dioxide, a greenhouse gas, has scientists alarmed.
Scientists estimate that average temperatures during the Pliocene rose as much as 18 degrees Fahrenheit. Sea levels during that 2.8-million-year epoch ranged between 16 to 131 feet higher than current levels, according to Richard Norris, a Scripps geologist.
"I think it is likely that all these ecosystem changes could recur," Norris said.
Heating the ocean probably will cause sea level rises and change the Ph balance of the ocean, affecting a wide array of marine life, he said. "Our dumping of heat and CO2 into the ocean is like making investments in a pollution bank."
The graph was instituted by climate science pioneer Charles David Keeling at Scripps. It is the longest continuous record of CO2 in the world, starting from 316 ppm in March 1958.
For the previous 800,000 years, CO2 levels never exceeded 300 parts per million. The level was about 280 parts per million at the advent of the Industrial Revolution in the 18th century, when the burning of fossil fuels began to soar.
"I wish it weren't true, but it looks like the world is going to blow through the 400-ppm level without losing a beat," said Scripps geochemist Ralph Keeling, who has taken over the Keeling curve measurement from his late father. "At this pace we'll hit 450 ppm within a few decades."