Carbon dioxide levels dating far back
Researchers have reconstructed atmospheric carbon dioxide levels over the past 2.1 million years in the sharpest detail yet, shedding new light on its role in the earth's cycles of cooling and warming.as the cause for earth's ice ages growing longer and more intense some 850,000 years ago.
In the study, Bärbel Hönisch, a geochemist at Lamont-Doherty Earth Observatory, and her colleagues reconstructed CO levels by analyzing the shells of single-celled plankton buried under the Atlantic Ocean, off the coast of Africa.But it also confirms many researchers' suspicion that higher carbon dioxide levels coincided with warmer intervals during the study period.The authors show that peak CO is at 385 parts per million, or 38% higher.There is more carbon dioxide in the atmosphere than there has been for 800,000 years — since before our species evolved.On Saturday (May 11), the levels of the greenhouse gas reached 415 parts per million (ppm), as measured by the National Oceanic and Atmospheric Administration's Mauna Loa Observatory in Hawaii.[8 Ways Global Warming Is Already Changing the World]During the ice ages, carbon dioxide levels in the atmosphere were around 200 ppm.
And during the interglacial periods — the planet is currently in an interglacial period — levels were around 280 ppm, according to NASA.
Monthly CO in order to understand how quickly fossil fuel pollution is changing our climate," said Pieter Tans, senior scientist with NOAA's Global Monitoring Division. They do not depend on any models, but they help us verify climate model projections, which if anything, have underestimated the rapid pace of climate change being observed." The concentration of CO in the atmosphere increases every year, and the rate of increase is accelerating.
The early years at Mauna Loa saw annual increases averaging about 0.7 ppm per year, increasing to about 1.6 ppm per year in the 1980s and 1.5 ppm per year in the 1990s.
A third theory challenges how the cycles are counted, and questions whether a transition happened at all.
The low carbon dioxide levels outlined by the study through the last 2.1 million years make modern day levels, caused by industrialization, seem even more anomalous, says Richard Alley, a glaciologist at Pennsylvania State University, who was not involved in the research.
"We know from looking at much older climate records that large and rapid increase in CO in the past, (about 55 million years ago) caused large extinction in bottom-dwelling ocean creatures, and dissolved a lot of shells as the ocean became acidic," he said.