A 15-Million-Year-Old Sedimentary Deposit in an Ancient Idaho Lakebed May Help Us Prepare for the Next 20–30 Years


In the past 100 years, “we’ve experienced more drastic climate change than any other human has ever experienced. There’s no analogy in human society,” says Hong Yang, the 2022–2023 William and Flora Hewlett Foundation Fellow. Since we cannot consult a historical record to see how past humans adapted to climate change, we turn instead to the geological one.
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One of the few glimpses the Earth offers of what our warming future could look like comes to us via 15-million-year-old sedimentary rocks and fossils found at a geological research site near the small town of Clarkia, Idaho (population less than 336). These layers of rock preserve a record of a time when atmospheric CO2 levels were very similar to where they will likely be in the next 20–30 years if we don’t control the current rate of greenhouse gas emissions.

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Yang went to college in Wuhan, China, and studied geology. “At the time, we were taught that we needed coal and petroleum deposits and gas fields for energy, but few people realized that burning fossil fuels creates emissions that cause climate change. As an earth scientist, I would have never dreamed something that in the past has happened over millions of years [climate change] could happen in the span of a lifetime,” says Yang, adding that it’s only in the past 10 or so years that scientists realized just how fast the rate of change is.

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Harvard Radcliffe Institute: How and why did you first become interested in studying climate change?

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Hong Yang: As an earth scientist, studying long-term climate change has always been a part of my profession. But the Clarkia site I’m working on gave me a fresh look at the rate and impact of climate change in the short term. When the site was discovered in the 1970s, it was significant geologically because it contains some beautifully preserved fossils and a suite of biomolecules like no other site. But only quite recently did we realize that the site may hold keys to understanding the near future of climate change. We recently dated volcanic ash embedded in sedimentary rocks that are around 15 million years old—a geological period known as the Miocene Climate Optimum. We were able to reconstruct that the CO2 level at this time was around 500–550 parts per million (PPM). That is roughly double the preindustrial level [preindustrial CO2 was around 280 PPM] but close to where we will be in the next few decades if we don’t control the current rate of emissions. And because the site is a lake deposit, we were able to demonstrate its annual resolution, giving us an unprecedented, high-resolution climate record of an ancient past with a near-future CO2 level. Essentially, it offers an “imaginary” picture of what this type of climate change—and associated ecological impacts—looks like.

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HRI: Could you describe in more detail the work that you are doing at Radcliffe?

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HY: My Radcliffe project has two components. The first one is scientific: continuing to work on the geological site that I mentioned. As part of a prior National Science Foundation–funded project, we looked at temperatures and CO2 changes during the Miocene Climate Optimum. Now, we’re focused on figuring out the role of another very important greenhouse gas, methane. We’re collaborating with Ann Pearson, who is a former Radcliffe fellow and now the chair of the Harvard Department of Earth and Planetary Sciences, and we have student Radcliffe Research Partners in the lab working on sediments from the Clarkia site.

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The second aspect of my project is educational. I am working with another Radcliffe Research Partner to explore how to best convey scientific information [about climate change]. Our current plan is to interview climate change education leaders and experts in the Harvard community and survey Harvard students. The question we are investigating is, “What kind of intellectual capacity or competency regarding climate change do college students, regardless of their majors, need in order to make sound arguments and to adapt to the new climate environment?” I’m also trying to collaborate with artists to visualize the impact of climate change based on what we’ve learned from the geological record. I haven’t identified a particular format yet but, later this month, I have artists coming from Ohio to visit me so we can brainstorm.

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