Earth’s hot past points to drastic global warming

WASHINGTON - A new analysis has concluded that the magnitude of climate change during Earth’s deep past suggests that future temperatures may eventually rise far more than projected if society continues its pace of emitting greenhouse gases.

Building on recent research, the study examines the relationship between global temperatures and high levels of carbon dioxide in the atmosphere tens of millions of years ago. It warns that, if carbon dioxide emissions continue at their current rate through the end of this century, atmospheric concentrations of the greenhouse gas will reach levels that existed about 30 million to 100 million years ago, when global temperatures averaged about 29 degrees Fahrenheit (16 degrees Celsius) above pre-industrial levels.

National Center for Atmospheric Research (NCAR) scientist Jeffrey Kiehl said that global temperatures might gradually rise over centuries or millennia in response to the carbon dioxide. The elevated levels of carbon dioxide may remain in the atmosphere for tens of thousands of years, according to recent computer model studies of geochemical processes that the study cites.

Kiehl focused on a fundamental question: when was the last time Earth’s atmosphere contained as much carbon dioxide as it may by the end of this century?

If society continues on its current pace of increasing the burning of fossil fuels, atmospheric levels of carbon dioxide are expected to reach about 900 to 1,000 parts per million by the end of this century. That compares with current levels of about 390 parts per million, and pre-industrial levels of about 280 parts per million.

Kiehl applied mathematical formulas to calculate that Earth’s average annual temperature 30 to 40 million years ago was about 88 degrees F (31 degrees C)-substantially higher than the pre-industrial average temperature of about 59 degrees F (15 degrees C).

The study will appear as a “Perspectives” piece in the journal Science. (ANI)