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Environment Report: How We Know Humans Are Warming the Planet

The intersection of Friars Road and Frazee Road. / Photo by Dustin Michelson

It happens every so often when I write about climate change. Somebody inevitably shoots me an email expressing doubt in the science.

Before taking this job, I spent a year probing this problem at Scripps Institution of Oceanography’s climate science and policy program. How is it, I wondered, that everyone doesn’t believe what 97 percent of scientists studying the earth’s climate agree on: Human activity is causing the earth to warm faster.

Earlier this week I laid out four climate change topics [1] important to San Diego. And once again, I got that skeptical email, but instead of a diatribe laden with links from questionable websites, the sender asked for more information. They asked: What connects human activity (i.e., using fossil fuels by driving cars or running factories) to climate change?

The climate change problem for some doubters is not centered on belief. It’s centered on a misunderstanding. That I can work with.

Enter Dillon Amaya, climate scientist at University of Colorado-Boulder, who recently gave a talk to students at San Diego State University [2] on this very topic. In addition to his research [3], Amaya gives public talks to regular people like me who have questions about climate change.

“Carbon dioxide is an invisible gas. If we could see it coming out of a tailpipe, this wouldn’t be a problem,” Amaya said. “But the fact that it’s invisible makes it so abstract; it’s hard for people to understand it’s there and rapidly accumulating.”

(A company called Carbon Visuals tried to envision a world in which carbon dioxide is visible [4]. One project shows the amount of carbon emissions generated by New York City as a pile of heavy blue blobs burying Manhattan.)

Carbon dioxide occurs naturally, even without humans stumbling around the planet. It makes up less than 1 percent of the gas in our atmosphere, but its ability to trap heat near the earth’s surface is what makes it special — and dangerous.

For the purposes of simplifying this explanation, you should know there are different kinds of carbon in carbon dioxide. Knowing the difference is how scientists can tell how much carbon dioxide came from humans burning fossil fuels.

You need to dig into your high school chemistry brain for a second here. Carbon dioxide is a molecule with one carbon atom attached to two oxygen atoms (“di” means two). The different “kinds” of carbon are categorized by how much they weigh — some atoms have more neutrons than others, meaning they quite literally weigh more.

Heavier carbon is called C-13. And lighter carbon is called C-12.

“Nature is super lazy and prefers to take up lighter carbon because it’s easier for plants and animals to process,” Amaya said.

So because plants gobble up the lighter carbon, humans and animals (who eat plants) are full of carbon that’s lighter. But what’s left behind in the air is the heavier carbon.

When animals and plants die and are buried in the earth for thousands of years, their bodies become the goo we call oil. That oil is full of the carbon that’s lighter than what’s left in the air.

This distinction is what scientists can chemically measure. We can tell when humans stopped banging each other over the head in caves and began revving up their Ford Quadricycle [5] because, at a certain point in history, a bunch of that lighter carbon was released into the atmosphere really fast, mixing in with the heavier carbon that was already there.

“We can see that ratio. It’s like if you mix something that’s hot with something that’s cold, we get something that’s warm,” Amaya said.

Suess effect
Image courtesy of M. Rubino/Journal of Geophysical Research

This graphic’s scary black line shows the amount of carbon dioxide in the atmosphere shooting up around the 1850s, otherwise known as industrialization. The yellow line shows the average “weight” of a carbon atom in the air over the same period. Notice at around the 1850s, the weight of the average amount of carbon in the air plummets because a lot of that lighter carbon was released by burning fossil fuels.

More on Fossil Fuels and the Franchise Fee

San Diego Gas and Electric will be the city’s power provider for another five months, though its 50-year contract with the city technically expires on Jan. 17. That’s because Mayor Todd Gloria reached a deal to extend it as the city figures out how it’s going to move forward.

Gloria canceled the process the previous mayor started, which was supposed to be a competitive bid for the lucrative contract (called the franchise fee agreement [6]) to operate and maintain the city’s electric poles and wires. But after much ado, it turned out that SDG&E was the only company to submit a bid.

The City Council unanimously agreed to the extension, which ends June 1. Advocates for a government-run power company (otherwise known as public power) had hoped that the city would ask SDG&E for a one-year extension, which is apparently the length needed to complete a thorough study of a public power agency. Nicole Capretz, the founder and executive director of Climate Action Campaign, said in a tweet [7] that five months is “just enough time to complete a business plan for public power.”

SDG&E is a gas company owned by Sempra Energy, an energy infrastructure company that builds and owns natural gas distribution networks in the Gulf of Mexico. Much of San Diego’s power is currently supported by the fuel, which is extracted by mining shale through hydraulic fracking [8].

It too emits carbon dioxide but at almost half the amount as coal. Therefore, it’s often marketed as a cleaner fuel. Natural gas mostly produces methane, which is the second leading contributor to global warming [9].

A new study by Yale’s Climate Change Communication program showed that Americans perceive natural gas more favorably [10] (76 percent favorable) than other fossil fuels like oil or coal. The study’s authors probed the question of whether we should continue to call it “natural gas” or just “methane.”

“We found that the term ‘natural gas’ evokes much more positive feelings than do any of the three methane terms,” the authors wrote.

Words matter.

Huge Cliff Collapse at Torrey Pines

Just days after my piece about the burgeoning science behind beach cliff collapses [11], a giant piece of Torrey Pines State Beach fell but luckily struck no one.

Video published by Fox 5 San Diego showed cell phone footage of a massive landslide [12], triggering screams from beachgoers. Multiple people lost their lives in recent years by just enjoying the beaches below towering and unstable sandstone cliffs.

I talked again with Adam Young, who is a geomorphologist from Scripps Institution of Oceanography, about this collapse. He’s compiled one of the largest datasets on the collapse vulnerability of Del Mar’s shores, but is still monitoring cliff faces in Torrey Pines and elsewhere in Southern California.

His research focuses on how rain and ocean waves eat away at a cliff’s stability. This collapse occurred after some of the largest rains we’ve had yet this winter.

“This event provides a reminder that many of the cliffs are unstable and can fail at any time,” he wrote.

The landslide was primarily from the upper cliff during low tide, Young wrote in an email. A similar sized landslide happened just south of that Torrey Pines location on July 3, 2019.

Young noted that bigger landslides like the ones seen in the video often unfold in a series of events marked by smaller, trickling landslides. That could provide a little bit of warning for beachgoers before a larger, potentially deadly collapse.

“The cliffs at Torrey Pines are particularly hazardous because tall and steep cliffs are capable of ejecting rock farther onto the beach,” Young said.

Policymakers may try to tackle erosion and other climate issues on the coast with bills this year. State Sen. Pat Bates wrote a letter to the editor [13] in response to my original story, disputing the characterization of a bill she wrote to address cliff collapses.

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