COLUMBUS, Ohio – Scientists are working to shed new light on an enduring climate mystery – one that, if solved, could help them make more accurate predictions about the planet’s future.
In a new study, data from ice cores collected from Greenland, Antarctica and various tropical mountains were compared to climate model simulations made of the Holocene, a geologic era that began about 11,700 years ago. Natural data and climate simulations of this time, specifically for Earth’s average temperature, have been puzzlingly at odds with each other, most notably in tropical mountains.
Discrepancies in the long-term trend between the model predictions and the natural proxy records have led researchers to call this mismatch the
Now, using oxygen isotope data from ice cores, researchers found that ice core data and computer models of the Holocene do match when analyzing polar regions like Greenland and Antarctica. However, that is not the case for Earth’s tropical mountains, said , lead author of the study and a postdoctoral scholar
“Current climate models posit that the planet experienced an early, steady increase in warming throughout the Holocene, but most of the paleoclimate samples suggest that later in the Holocene Earth experienced a global cooling period,” said Bao.
The team found that ice core data from tropical mountains like in Tanzania and in Peru suggest possible cooling by 0.8 to 1.8 degrees Celsius, whereas models suggest a prolonged warming by 1.5 degrees.
These climate variations were driven by orbital forcing, or changes in the Earth-sun orbit that influence the global climate. However, the model-data mismatch over tropical mountains presents a challenge for researchers in explaining the underlying causes of tropical mountain oxygen isotopic ratios and the associated temperature changes during the Holocene. Climate simulations also tend to overlook important factors, such as vegetation and land use, that could have influenced Holocene temperatures, said Bao.
“All models have different kinds of uncertainties,” he said. “But by using ice core isotopic data as a guide, we can find a better way to evaluate how good or how bad our climate models are.”
The study was recently published in the journal
The type of simulation the researchers used to address the conundrum is called the a system that incorporates global details like atmosphere, ocean, land and river runoff components to build precise past and future climate projections.
While scientists are still unclear on why the model fails to explain the mechanisms behind these discrepancies over the tropical mountain areas, the study does note that no single factor, such as global temperature fluctuations or heavy rainfall, could effectively explain these Holocene-era patterns.
Still, putting effort into understanding these issues is well worth it to improve future paleoclimate interpretations, said , co-author of the study and a professor
“This type of study is extremely important because we’re looking at both the shortcomings in the data and the models,” he said. “The natural world is very complex, so when you try to capture this and put it into a model, that’s a big job.”
Most climate models that don’t account for feedbacks like land use, vegetation, dust and volcanic emissions aren’t as accurate at predicting the natural world, said Thompson. On the other hand, proxy data collected from ice cores are some of the most reproducible types of climate evidence from one century to the next, so paleoclimatologists consider them reliable narrators of Earth’s complex history.
“If technology cannot capture these very subtle natural variabilities, then it raises big questions about what its output says for the future,” Thompson said.
The study concludes by calling for the paleoclimate community to help refine global climate models and bolster future climate projections, especially during a time when Earth is experiencing rapid biodiversity losses.
“Big breakthroughs in science are going to come along the boundaries of collaboration,” said Thompson. “We can work together to tackle these issues.”
Co-authors include Zhengyu Liu and Ellen Mosley-Thompson from Ohio State, as well as Lingfeng Wan from Ocean University of China and Jiuyou Lu from Laoshan Laboratory in China. The study was supported by the National Science Foundation and the National Oceanic and Atmospheric Administration.
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Contact: Yuntao Bao, [email protected], Lonnie Thompson, [email protected]
Written by: Tatyana Woodall, [email protected]
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