Carbon emission rate is highest in 66M years, study finds

The rate of carbon emissions ishigher than at any time in fossil records stretching back 66million years to the age of the dinosaurs, according to a studyon Monday that sounds an alarm about risks to nature fromman-made global warming.

Scientists wrote that the pace of emissions even eclipsesthe onset of the biggest-known natural surge in fossil records,56 million years ago, that was perhaps driven by a release offrozen stores of greenhouse gases beneath the seabed.

That ancient release, which drove temperatures up by anestimated 5 degrees Celsius (9 Fahrenheit) and damaged marinelife by making the oceans acidic, is often seen as a parallel tothe risks from the current build-up of carbon in the atmospherefrom burning fossil fuels.

"Given currently available records, the presentanthropogenic carbon release rate is unprecedented during the
past 66 million years," the scientists wrote in the journalNature Geoscience.

The dinosaurs went extinct about 66 million years ago,perhaps after a giant asteroid struck the Earth.

Lead author Richard Zeebe of the University of Hawaii saidgeological records were vague and "it's not well known if/howmuch carbon was released" in that cataclysm.

Current carbon emissions, mainly from burning fossil fuels,are about 10 billion tonnes a year, against 1.1 billion a year
spread over 4,000 years at the onset of the fast warming 56million years ago, the study found.

The scientists examined the chemical makeup of fossils oftiny marine organisms in the seabed off the New Jersey in theUnited States to gauge that ancient warming, known as thePaleoeocene-Eocene Thermal Maximum (PETM).

U.N. studies project that temperatures could rise by up to4.8 C this century, causing floods, droughts and more powerfulstorms, if emissions rise unchecked. Carbon dioxide forms a weakacid in seawater, threatening the ability of creatures such aslobsters or oysters to build protective shells.

Effects of current warming more severe

"Our results suggest that future ocean acidification andpossible effects on marine calcifying organisms will be more
severe than during the PETM," Zeebe said.

"Future ecosystem disruptions are likely to exceed therelatively limited extinctions observed at the PETM," he said.
During the PETM, fish and other creatures may have had a longertime to adapt to warming waters through evolution.

Peter Stassen, of the University of Leuven who was notinvolved in the study, said the study was a step to unravel whathappened in the PETM.

The PETM "is a crucial part of our understanding of how theclimate system can react to carbon dioxide increases," he toldReuters.