The scientists went on to say that many of the mountain-top glaciers in Africa and tropical South America are in danger of disappearing within the next 15 years -- and little, if anything, can be done about it. The new data was presented on Sunday at the annual meeting of the American Association for the Advancement of Science in San Francisco.

The scientists called the findings a clear sign of global warming - and, while they agreed that some glacier advances and retreats are cyclical in nature, the changes that they are seeing cannot be attributed totally to natural causes. We'll find out more.

Also last week, as this data was being presented in San Francisco, scientists and policymakers met in Geneva as part of the Intergovernmental Panel on Climate Change. There they accepted a report looking at both natural and human-caused changes to the climate. The report found that recent climate changes have already affected many biological and physical systems, from shrinkage of glaciers to earlier egg-laying in birds. Further, climate changes may produce other effects - from disease outbreaks to increased food prices. We'll talk about the report and its findings.

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