The tipping point: Researchers look to the past and the future of Earth’s climate

Sheets of ice float atop a calm ocean. The sun appears muted behind a layer of clouds.

(Kai Boggild/ BY 3.0)

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By Chelsea Zhao

In a climate report published in October of 2022, the United Nations Environmental Program stated that current UN policy will lead to a global 2.8°C temperature rise by the end of the century.

As threats loom and deadlines near, two fellows of the Comer Climate Conference have worked to determine the concrete effects of climate change in their research, looking at both the past record and future predictions of the Earth’s processes. 

Looking toward the past

Crystal Rao, a Geoscience graduate student at Princeton University, bases her research on past environmental changes and their impacts on species using analysis of isotopes, or different forms, of Nitrogen in fossils. Rao uses the ratio of two common forms of nitrogen as a standard, and compares it with the nitrogen inside the tooth tissue of the megalodon shark. 

From there, she reconstructed a picture of the trophic level, or the position on the food web, where a megalodon shark is at the top. Rao said, due to its high rank in the energy level, the megalodon could “basically eat anything in the ocean.”

A size comparison of a dark brown megalodon tooth next to two smaller great white teeth. Fossils such as this large tooth are what Rao has studied to learn about past changes in climate.
A megalodon tooth next to two great white shark teeth. (Wikimedia Commons/CC BY-SA 3.0)

However, this species of shark, roughly 50 feet long, suddenly went extinct 3.5 million years ago. Rao said as the climate changed, the food source the sharks relied on to fuel their massive body depleted and eventually led to their deaths.

In other words, a shift in climate broke the existing food chain balance, potentially leading to the downfall of an entire species. “As climate shifts, maybe the production in the ocean could change,” Rao said. “And depending on what the ecosystem responded to, there could be less food availability for those Megalodon sharks.”

Eyes on our climate future

While Rao’s work examines a species belonging to an ancient era, another Comer scientist’s work takes estimation into the possibilities of the future. 

Edmund Derby, Climate Science Ph.D. student at Oxford University, utilizes simple models of Arctic sea ice from his past research in 2009 to examine the bifurcation or tipping point accompanying ice cover changes throughout the season. 

Derby’s research presents climate from basic principles to its core behavior. In the scientific model, when atmospheric carbon dioxide exceeds a certain point, after all the Arctic ice melts, it is no longer possible to gain back the ice. His model investigates this tipping point under a model when the Arctic is covered in ice all year round. 

“When you’ve reached this tipping point, you don’t get a reversible change once you’ve lost your ice cover,” Derby said. 

The temperature of the Arctic is intrinsically connected with the rest of the world. In a phenomenon known as Arctic Amplification, the Arctic warms twice as fast as the rest of the world. As the light-reflective ice melts, it gives way to more heat-absorbent ocean water. 

According to Derby, the difference in temperature between the Arctic and at the lower latitudes determines the rate of Arctic temperature rise.  

This is an example of sensible heat transport: Heat moves from colder to warmer objects when they are in close proximity. In the same sense, as the Arctic warms up, the transfer of heat to the Arctic decreases. 

However, in a changing climate, the transport of water vapor or clouds into the Arctic can counteract the cooling of this cold to warm heat transfer. The water vapor causes local temperature in the Arctic to rise. 

In his research, Derby is adding more factors into the model to make it more realistic to the Arctic ice cover, and to investigate whether the global rise of greenhouse gas will impact the ice melt at a local level. 

Rao said in her field of geoscience, the past informs the future. Studying the ancient past of Earth’s environment builds a better understanding of the complex systems involved. “Only when we can really understand or estimate the future better, then we can come up with better plans in terms of how we do climate adaptation and climate mitigation,” Rao said. 

The numbers of climate change may seem small, but in the timescale of millenia, a small change now may mean a colossal shift into the future. 

Through Rao and Derby’s research, of both the past and the future, concerns of climate change continue to loom in both the vanishing fabric of the Arctic and the demise of a species. 

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Biodiversity, climate change, comer conference 2022, glacial warming

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