Video courtesy of the NSF.
Past Climate Changes and Uncertainty
Climate scientists use "proxy data" to study climates of the past, before humans with thermometers began keeping temperature records. These "proxies" include tree rings, layers within ice cores pulled from glaciers and ice sheets, growth layers in coral, and layers of sediments from the bottoms of lakes and oceans.
By combining data from various proxies, climate scientists have been able to determine the history of Earth's climate extending back millions of years into the past. The proxies don't give us a precise measure of temperature; the temperature history they provide is a bit "fuzzy". However, even with this uncertainty, the data clearly shows that recent global warming outpaces any natural temperature rise that has occurred within thousands of years.
It is important to distinguish between uncertainty and disagreement. The vast majority of climate scientists and organizations that study weather and climate agree that our planet is currently experiencing a very unusual period of rapid warming.
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