Scientists find proof that Carbon Dioxide is leading to Global Warming

NEW YORK: Global warming that happened some 55 million years ago might be the result of the Earth's sensitivity to long-term release of carbon dioxide, according to the findings of a new study. And carbon dioxide could play a vital role in the present-day global warming as well, the study predicts.

However, the study, by Mark Pagani, an associate professor of geology and geophysics at the Yale University and his team, contradicts views held by some of the climatologists that the Earth's system is resilient to such emissions.

Details of the study appear in the Science magazine.

Scientists had studied a global warming event some 55 million years ago, called the Paleocene-Eocene Thermal Maximum (PETM) and believed that it was caused by a huge release of carbon into the environment.

It is estimated through studies that the resulting greenhouse effect heated the planet by about 5 deg. Cel. on an average, in less than 10,000 years. The impact had lasted for 170,000 years and led to widespread changes including mass extinction in the oceans due to acidification and shifts of plant communities due to changes in rainfall. The phenomenon also led to the age of mammals, including the evolution of modern primates.

However, scientists have not been able to understand just how much carbon was responsible for the temperature increase and where it came from.

Pagani and his team used data from carbon found in fossils of ancient land plants and tiny marine organisms known as plankton, which established that the amount of carbon released to the atmosphere and ocean was more or less the same as what is available today as coal, oil, and gas.

Pagani says, "It is a stunning example of carbon dioxide-induced global warming and stands in contrast to critics who argue that the Earth's temperature is insensitive to increases in carbon dioxide."

Ken Caldeira, a co-author of the study and researcher at the Carnegie Institution's department of global ecology, says the carbon heated up the Earth for over 100,000 years. If the climate was as insensitive to CO2 as the climate skeptics claim, there would be no way to make the Earth so warm for so long, he says.

The scientists are not sure of the source of this carbon. They surmise it could have come from massive fires burning coal and other ancient plant material, or from "burps" of methane from the continental shelves.

If the source was ancient plant material, then for each doubling of atmospheric CO2 concentration, the Earth would warm at least 2.2 deg Cel. If it was methane, as many believe, the situation is more critical, because the methane would have become carbon dioxide in the atmosphere within decades.

The researchers believe it would now be available to cause climate change, which means that the climate is even more sensitive to added CO2 than earlier believed.

At the current level of use of coal, oil and gas, atmospheric CO2 concentrations are expected to double around the middle of the century. This will be added to the CO2 concentrations created as a result of the ancient emissions. Hence, if human-induced carbon emissions continue unabated, there could be a possibility of a shift in species evolution.

Caldeira says the last time carbon was emitted to the atmosphere on the scale of what we are doing today, "there were winners and losers. There was ecological devastation, but new species rose from the ashes. Luckily for us, our ancient primate ancestors were winners. Who knows who the winners and losers will be in the next go round."