JUNCTION, Texas (AP) - Halfway up a steep dirt embankment alongside Interstate 10, Marina Suarez grabbed what looked like a gray rock and stuck it triumphantly in the air.
“I found an oyster!” the geologist exclaimed.
The San Antonio Express-News reports hundreds of fossilized shells had tumbled from an ancient oyster bed into the cakey, crumbling wall of dirt and mudstone under Suarez’s boots.
Suarez, three colleagues and two students had arrived to collect chunks of gritty gray and brown rock they carved out with rock hammers.
In her lab, Suarez, 36, will clean, pulverize and combust tiny samples of this rock to tease out secrets about how greenhouse gases in the atmosphere changed the global climate from around 112 million to 110 million years ago.
Suarez is an assistant professor at the University of Texas at San Antonio who studies climates of the past. She’s interested in the carbon cycle, a web of exchange that connects the Earth’s crust, the oceans, the atmosphere and all living things.
Last year, the National Science Foundation awarded Suarez a $480,000 grant to study these time-hardened soil beds from the middle of the Cretaceous Period.
What she learns about global warming in the past might help scientists better understand how the planet is responding to global warming today.
“These changes that we’re looking at, we think of it as pretty fast, geologically speaking,” she said. “But it took 800,000, 900,000, up to 2 (million) to 3 million years.”
Even over that long time scale, the Earth experienced massive species die-offs and the global collapse of ocean reefs. Today, scientists speak of similar consequences of global warming unfolding over hundreds of years.
“I think a lot of the concerns that scientists have are about the rate of these changes,” Suarez said.
Last month, Suarez and her group spent about eight hours painstakingly measuring, collecting and bagging 53 samples from the embankment.
Suarez is no stranger to long days in the field. At age 23, the San Antonio native and her twin sister, Celina, were doing field work in Utah when they found a small bone from a new dinosaur species, later named Geminiraptor suarezarum. Her sister now studies and teaches geology at the University of Arkansas.
“How many twins have a dinosaur named after them?” said Thomas Adams, paleontology and geology curator at the Witte Museum, who joined the group that day in the field.
Along the interstate, trash and tire chunks obscured the embankment’s long geologic history. At one point, it probably was a layer of soil with plants growing in it and small rivers or streams nearby, Suarez said.
Back then, the Gulf of Mexico was beginning to form, Europe was a cluster of islands in a shallow sea, and South America and Africa were close together. Dinosaurs walked through what would become Texas. More familiar life - like birds, flowering plants and pollinating insects - began to emerge and populate the planet. It was a time of global warmth with tiny or nonexistent polar ice caps.
Global climate change in the mid-Cretaceous probably was driven by the gases spewed by massive volcanoes that erupted as the continents drifted apart, Suarez said.
Over the next five years, Suarez will further investigate this idea using rock samples from near Junction and three other sites in Utah, Spain and China.
“We’re interested in fluctuations in the atmospheric carbon,” Suarez said.
These rocks will show her the origin of the greenhouse gases in the atmosphere of the Cretaceous, particularly carbon dioxide, today the most important greenhouse gas.
Suarez is looking for the ratio of the two common isotopes of carbon. There’s carbon 12 and its ever-so-slightly-heavier sibling, carbon 13. Carbon 13 usually comes from inorganic sources, such as volcanoes, while carbon 12 is tied to living things.
Scientists can see the carbon dioxide in today’s atmosphere, Suarez said. The lighter the carbon, the more likely it came from organic material. In today’s world, that means fossil fuels like coal, oil and natural gas.
“Since the Industrial Revolution, (atmospheric) carbon is very light in its composition,” she said.
From their perch on the road cut, Suarez’s group could easily see examples of what’s causing today’s warming. Diesel trucks whizzed by on the interstate, and two exhaust stacks from burners at a local manufacturer, Cedar Fiber Co., rose from the banks of the Llano River.
Fossil fuel emissions have fueled a rise of 1.68 degrees Fahrenheit in average global surface temperatures since record-keeping began in the late 1800s, according to the National Oceanic and Atmospheric Administration. Global temperatures set heat records in 2016 for the third year in a row.
“It actually kind of makes sense if you think about it,” Suarez said. Much of the carbon now buried underground was deposited when the planet was much warmer, in a state some scientists call Greenhouse Earth.
“If we were to take it out of the ground and put it back in the atmosphere, it’s not terribly surprising that we would see an increase in global temperatures,” she said.
Under President Donald Trump, federal efforts to address climate change are being dismantled.
Trump recently announced he would not fulfill the U.S.’ nonbinding commitments under the Paris climate accord, and the administration has moved to roll back Obama-era regulations meant to reduce greenhouse gas emissions.
In the past, Trump has called climate change a “canard” and a “hoax” on Twitter.
Many people who try to deny the science that explains man-made global warming often point to nonhuman causes like solar activity or volcanoes to explain today’s climate shifts. But those explanations don’t hold up to evidence, Texas State Climatologist John Nielsen-Gammon said.
“Climate is always changing,” Nielsen-Gammon said by phone. “We know pretty well the things that cause it to change.”
Those that humans can’t control include solar activity, volcanoes and cyclical interactions between the oceans and atmosphere, he said. Humans do have control over greenhouse gases from fossil fuels and the conversion of forests and other wild landscapes to cities and agricultural land.
“If you just look at the balance sheet in terms of how much each of those affects the energy coming into the Earth and going out, the change in atmospheric composition of greenhouse gases is by far the biggest current factor,” Nielson-Gammon said. “Since the middle of the 20th century, all the other potential candidates are not only much weaker, but most of them would actually have a cooling affect instead of a warming effect.”
Climate modelers predict continued warming will lead to rising sea levels, more extreme storms, droughts, wildfires and the collapse of the world’s coral reefs.
When Suarez thinks about these effects, her mind goes to her young nephew. She wants him to be able to experience the same planet she’s dedicated her life to studying.
“Just to think that my nephew will probably never get to see the Great Barrier reef when he’s older,” she said on the drive back to San Antonio. “It freaks me out more for my nephew and for kids. . We’ll have a lot of changes.”
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Information from: San Antonio Express-News, https://www.mysanantonio.com
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