An international study used tree rings and pollen to build the first record of global climate change, continent by continent, over 2,000 years.
Courtesy Thomas Beer/AP/File
A reconstruction of 2,000 years of global temperatures shows that a long-term decline in Earth's temperatures ended abruptly about 1900, replaced by a warming trend that has continued despite the persistence into the 20th century of the factors driving the cooling, according to a new study.
Indeed, for several continents, the increase in global average temperatures from the 19th century to the 20th was the highest century-to-century increase during the 2,000-year span, the study indicates. It's the first study to attempt building a millennial-scale climate history, continent by continent.
The research wasn't designed to identify the cause of the warming trend, which climate researchers say has been triggered by a buildup of greenhouse gases – mainly carbon dioxide – as humans burned increasing amounts of fossil fuel and altered the landscape in ways that released CO2.
Still, it's hard to explain 20th-century warming without including the influence of rising CO2 levels, because the factors driving the cooling were still present, notes Darrell Kaufman, a researcher at Northern Arizona University and one of the lead authors on the paper formally reporting the results in the journal Nature Geoscience.
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