Research Could Serve as a Warning on Global Warming Danger

Carbon dioxide levels in the atmosphere fluctuated after one of the ice ages, helping to heat up Earth’s climate and trigger the spread of deserts thousands of years ago, Swiss and American researchers report in today’s Nature. Scientists say the findings --could serve as a warning for Earth in the 21st century.

Carbon dioxide in the atmosphere is called a “greenhouse gas” because it traps the sun’s heat. Levels of carbon dioxide fell and rose between 11,000 and 1,000 years ago, and the fluctuations correlate with droughts and the spread of deserts in Africa and Asia during the prehistoric period known as Holocene. These ancient carbon dioxide levels, while significant, were far lower than the rising concentrations in today’s atmosphere.

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Compiled by Times medical writer Thomas H. Maugh II