MYTH: The current climate changes are within the Earth's natural variability.

	Photo: © iStockphoto.com/Felix Möckel

FACT: The Earth's climate is influenced by a few natural variations. For instance, the Earth's orbit changes from circular to elliptical over 98,000 years. Its tilted axis also wobbles between 22 and 25 degrees roughly every 41,000 years. Both of these factors contribute to warmer summers and winters that can cause ice sheets to melt in higher latitudes. This in turn can cause additional heating because there is less ice to reflect the sun's energy back into space; thus, less carbon dioxide is absorbed.

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Despite these natural variations, it has been shown through scientific testing that more recent temperatures highly exceeded the natural range over the last 650,000 years. Scientists have been able to determine this by plotting data received from prehistoric climate indicators, such as polar ice cores and tree-ring samples, as well as more modern temperature gauges.