Researchers caution temperatures will rise another 2.0 to 11.5°F by the end of this century
The global temperature today is warmer than at any time in the past 11,000 years, say scientists at the Oregon State University and Harvard University in the US.
Using data from 73 sites around the world, the group of scientists reconstructed earth’s temperature history dating back to the end of the last Ice Age. The findings show that planet today is warmer than it has been during 70 to 80 per cent of the time over the last 11,300 years, also called the Halocene period.
Lead author Shaun Marcott said that previous research on past global temperature change has largely focused on the past 2,000 years. “Extending the reconstruction of global temperatures back to the end of the last Ice Age puts today’s climate into a larger context,” said Marcott who is post doctoral researcher at the College of Earth, Ocean and Atmospheric Sciences in the Oregon University. “The finding is particularly interesting because the past 11,300 years spans the entire period of human civilisation,” he added.
This study is also important because many previous temperature reconstructions were regional in nature and were not placed in a global context, said Peter Clark, palaeontologist at Oregon University.
The researchers have explained how temperature has increased over the centuries. Warm conditions continued until the middle of the Halocene period followed by a cooling period over the past 5,000 years where the earth cooled about 1.3 °F until the last century. Then it started warming up again and in just 100 years it covered 1.3 °F. The warming up has been increasing since then.
The scientists used fossils from ocean sediment cores to reconstruct the temperature history. They tracked temperature by studying chemicals in the shells of tiny, fossilised sea creatures called foraminifera. The authors then combined different records into a master “stack”, and the pattern that emerged shows a rise in temperature as the last ice age ended.
The researchers also caution that global temperatures will rise another 2.0 to 11.5 °F by the end of this century mainly because of carbon emissions. “This warming will be significantly greater than at any time during the past 11,300 years,” said Clark. The reasons attributed for the warming are anthropogenic and gradual change in the distribution of solar insolation in relation to earth’s position.
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