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Scientists resolved a controversial but key climate change mystery

Revised Holocene temperature record affirms the role of greenhouse gases in recent millennia.

Holocene temperature conundrum is a long-standing mystery, with certain cynics fighting that climate model predictions of future warming must be wrong. A new study challenges long-held views on the temperature history in the Holocene era.

Scientists from Rutgers Institute of Earth, Ocean, and Atmospheric Sciences have resolved this long-standing mystery, suggesting that today’s annual global temperature is the warmest of the past 10,000 years. Their study shows that the first half of the Holocene was colder than in industrial times. The reason behind this was the cooling effects of remnant ice sheets from the previous glacial period.

Lead author Samantha Bova, a postdoctoral research associate, said, “The late Holocene warming was indeed caused by the increase in greenhouse gases, as predicted by climate models, and that eliminates any doubts about the key role of carbon dioxide in global warming.”

Using marine calcareous fossils from foraminifers– single-celled organisms that live at the ocean surface, scientists were able to reconstruct the temperature histories of the two most recent warm intervals on Earth: the Last Interglacial period from 128,000 to 115,000 years ago and the Holocene. They collected fossil samples by collecting a core of bottom sediments near the Sepik River’s mouth off northern Papua New Guinea during the Rutgers-led Expedition 363 of the International Ocean Discovery Program.

Scientists resolved a controversial but key climate change mystery
Photo: IODP-JRSO

How temperature evolved during the Last Interglacial and Holocene eras is dubious. Some data propose that the average annual global temperature during modern times doesn’t surpass the glow in the Holocene’s early warm period, called the “Holocene thermal maximum,” which was trailed by global cooling. Climate models strongly recommend that global temperatures have ascended all through the past 10,000 years in the interim.

Co-author Yair Rosenthal, a Distinguished Professor in the Department of Marine and Coastal Sciences and Department of Earth and Planetary Sciences at Rutgers University-New Brunswick, said“The apparent discrepancy between climate models and data has cast doubts among skeptics about the role of greenhouse gases in climate change during the Holocene and possibly in the future. We found that post-industrial warming has accelerated the long and steady global warming trend throughout the past 10,000 years. Our study also underscores the importance of seasonal changes, specifically Northern Hemisphere summers, in driving many climate systems. Our method can, for the first time, use seasonal temperatures to come up with annual averages.”

Other co-authors of the study include Shital P. Godard, a former Rutgers researcher now at National Taiwan University. Scientists at The Ohio State University and Nanjing Normal University contributed to the study.

Journal Reference:
  1. Bova, S., Rosenthal, Y., Liu, Z. et al. Seasonal origin of the thermal maxima at the Holocene and the last interglacial. Nature 589, 548–553 (2021). DOI: 10.1038/s41586-020-03155-x

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