After more than a decade as one of its stand-out employees, she received a surprise call from an Exxon vice president in 2020 and was fired. She was told her values no longer aligned with the company, but she blames something else: her decision to join colleagues in raising the alarm on oil drilling projections they believed were vastly inflated — to the tune of $10 billion or more. (Exxon disputes Gulden’s claims.)

Gulden has fought her dismissal for years now, including by filing a wrongful termination complaint with the government against Exxon, in a type of case in which employees prevail less than 2 percent of the time.

More than one person has advised her to let it all go, including her husband, who’d also worked at Exxon and left before her. The global giant, valued at about $464 billion, was too formidable, with platoons of lawyers ready to take on all adversaries.

But Gulden had to do something, she told the audience at a 2024 national whistleblower event on Capitol Hill. “I realized that if I didn’t stand up,” she said, “I would be complicit.”

Gulden’s decision to speak out has sent shock waves through the highest levels of Exxon and beyond. Her name has been linked to additional legal cases against the company, including one brought by shareholders that has pulled in the CEO and other executives. News stories chronicling the twists in the saga have been followed by swings in Exxon’s value on the stock market.

This wasn’t how Gulden expected her life to play out. Back in high school and headed for Harvard, Gulden was surprised when her classmates voted her “most likely to be president.” None of them, she says now, would ever have named her “most likely to be fired by a Fortune 500 company.”

In 2009, when Gulden and her husband, Enrique Rosero, had just started their jobs, she knew some of her environmentalist friends might raise their eyebrows. A climate scientist working for Exxon? Wasn’t that like an oncologist taking a job at Philip Morris?

But Gulden is not easily pigeonholed. She grew up in a Midwestern family where US industry was seen as a force of good, and she saw that in Exxon. It was in the midst of rebranding itself as a modern energy company, one that had the skill, money, and wherewithal to effectively help combat global warming. It felt exciting to be a small cog in a big machine, helping it grind toward change.

So even when Gulden’s own husband began to question the depth of Exxon’s commitment to the environment, she encouraged him to share his concerns with supervisors. The company repeatedly urged employees to speak up when they saw a problem — to show “courage of conviction,” as they put it. That’s how, together, they could make Exxon better.

Gulden believed all of it. It was in her nature to be an optimist.

The world still needs a lot of oil and gas, she’d say to her husband. Change takes time.

“Honey,” she insisted. “It’s going to be OK.”

Gulden and Rosero met in 2006 when they were pursuing PhDs at the University of Texas at Austin, both studying climate science. Their first date included a passionate exchange about statistical modeling.

The two came from different parts of the world. Gulden grew up in Columbus, Indiana, where she captained the cross-country team of her public high school and was named valedictorian of the class of 1996. In her graduation speech, she spoke about the charitable works of her classmates, not her own accomplishments. At Harvard, she ultimately majored in computer science.

Rosero was raised in Quito, the capital of Ecuador, and attended an all-boys Jesuit Catholic school before enrolling in one of his country’s top engineering colleges. His father worked as a manager for Petroecuador, the country’s national oil company.

Enrique Rosero and Lindsey Gulden during a training session for ExxonMobil in 2010.From Lindsey Gulden

In graduate school, the couple shared a sense of fun — driving around to try all kinds of Texas BBQ, watching Breaking Bad, and hosting parties with friends. They also shared a “principled approach to life,” says Lizzy Wright, Gulden’s former Harvard roommate, now a writer in California. “Some people need social approval. They aren’t that way,” Wright says. “No keep up with the Joneses there.”

The couple did care deeply about the environment. They were in graduate school for the 2006 release of the book and documentary An Inconvenient Truth, Al Gore’s climate action call to arms. But they also prided themselves on being pragmatic about potential solutions. Individual acts were important, but global industry had the chance to make a difference on a worldwide scale.

When Exxon recruited the freshly minted PhDs, each saw an exciting opportunity. Exxon was “the most technologically advanced company to work for, probably the most respected in the industry,” Rosero says. It also paid well, starting them each around $125,000 a year. Many top performers could nearly double that salary in a decade.

By 2009, Gulden and Rosero worked out of an Exxon office building in Houston. They landed in different departments: Gulden focused more on data analysis, Rosero more on oil production forecasting.

Working there often felt like being part of a family. When the couple married in 2011, many of their new friends from work were in attendance. And with the birth of their daughter in the summer of 2012, their family at home grew to three.

On a work trip a couple months later, Rosero and some colleagues flew on a jet over vast terrain in northeastern Alberta, Canada, controlled by Exxon, an area known as the Kearl Oil Sands. Rosero knew, intellectually, why projects such as this tended to generate the most controversy — squeezing petroleum from oil sands is considered one of the most environmentally damaging extraction methods.

But as the plane descended, Rosero saw for the first time, with his own eyes, the gigantic open-pit mines, some stretching several miles across. “You see this hole that is black — and it’s eye opening,” he says.

This is destructive on a massive scale, he recalls thinking. He thought of his new baby back home. This is the impact that the industry and my work is having. And we’re doing this to the planet that she’s going to live in.

Back at home, Gulden did her best to buck him up, encouraging him to speak to management about how Exxon could at least mitigate the damage.

The two settled into a dynamic: His deepening pessimism countered by her seemingly limitless optimism. In 2015, Inside Climate News put out a scathing report, alleging Exxon executives had hidden what they knew about global warming from as far back as the late 1970s. It would later prompt numerous states, including Massachusetts, to file suit against Exxon claiming deceptive practices. The story rattled many employees in Exxon’s headquarters, and Rosero’s spirits sank further.

Mining operations at Kearl Oil Sands in Alberta, Canada.Alamy Stock

Gulden was disturbed too, but she pushed down her worries. This was in the past, she thought. The company is changing.

She encouraged Rosero to raise questions at staff meetings — even at larger forums . “We took it seriously that they wanted to know what we thought,” Gulden says.

Rosero’s complaints did not seem to have job consequences at first. His supervisor gave Rosero strong marks in his annual reviews from 2016 to 2019, copies of which he shared with the Globe Magazine. Some of his discontent was being noticed, though. In one review, a manager suggested Rosero monitor his “tone” during disagreements.

Rosero didn’t see this as a major rebuke — he believed most Exxon managers and colleagues he worked with saw him as cordial. Many praised him privately, he says, for challenging management on global-warming issues. He was “the conscience of the geoscientists,” says one former Exxon colleague, who asked to remain anonymous for fear of career repercussions.

In 2019, Exxon supervisors granted Rosero’s wish to work at least part of each week on a “carbon capture and storage” project — the goal was to trap carbon dioxide from burning fossil fuels underground, rather than release it into air.

That was a project Rosero could get behind. He eagerly took up the assignment.

The Permian Basin, the largest petroleum-producing area in the United States, spans some 75,000 square miles, straddling swaths of Texas and New Mexico. Many of the industry’s biggest players scramble for supremacy there, including Chevron, ConocoPhillips, and Exxon. In 2017, Exxon acquired a new part of the area for about $6 billion — making its total holdings there roughly equal to the size of Delaware .

The investment appeared to promise big returns. In March 2019, Exxon issued a press release announcing plans to drastically boost production. “ExxonMobil said today it has revised its Permian Basin growth plans to produce more than 1 million oil-equivalent barrels per day by as early as 2024,” the release said, “an increase of nearly 80 percent.”

The company’s investments were “expected to produce double-digit returns, even at low oil prices,” the release went on to say, though it also included a long “cautionary statement” for investors: Future-looking statements are no guarantee of actual results, and predictions are subject to change based on market forces and other factors.

The company’s ambitious predictions would also be filed with the US Securities and Exchange Commission. Shareholders depend on such filings to make informed decisions.

Exxon’s 1 million barrels per day announcement shocked some of the technical staff affiliated with the Permian Basin project, including Gulden and a fellow computational scientist named Damian Burch. The figure seemed to them off — way off.

An aerial view of a part of the Permian Basin oil field in Texas taken in 2022. The Permian Basin is the largest petroleum-producing area in the United States, roughly the size of Florida.Joe Raedle/Getty Images

In the months ahead, according to a federal investigative report that came later, Burch and other specialists told top managers that the 1 million figure appeared vastly inflated. Their calculations suggested the accurate number was closer to 600,000. (Gulden would later conduct additional analysis that backed up the lower estimate.)

Gulden and Burch weren’t engaging in random mathematical exercises. If wrong, the higher number could artificially inflate Exxon’s valuation of its petroleum holdings in part of the Permian, known as the Delaware Basin, by an estimated $10 billion or more.

But instead of revising the estimates downward, Burch alleges, a high-level manager essentially told him to make the math work.

“We were asked to turn the knobs so we can get to a million,” Burch says.

He says the manager pressured him to add to the analysis a hypothetical “learning curve,” a concept that says drilling efficiency can become faster over time. With a strong enough learning curve factored in — one that would be unrealistic for this particular project, Burch said— the math could support the million barrel estimate Exxon executives had already been touting in press releases and public filings.

Burch, who holds a doctorate in applied mathematics, says he did as he was told and produced the requested spreadsheet with the learning curve variable. But because he worried his work might be used by the company to justify inflated predictions, he gave the file a special name: “Please_do_not_turn_this_into_a_lie.xlsx.”

Over time, Gulden and Burch each grew more deeply concerned about potential misuse of the data. In the fall of 2019, they did what they were always told to do if ethical issues emerged at work: They relayed their concerns to Exxon’s human resources department. They both say they were thanked, and were promised HR would look into it.

Gulden felt relieved after speaking up — like she’d saved the company from a serious mistake. She threw herself back into other projects, and didn’t think much more about it.

In 2020, about eight months after meeting with HR, Gulden’s manager delivered her performance review. Giving her an overall rating of “excellent,” he praised her talents for leading her team through change and juggling “a very significant portfolio of projects.”

But the manager also had a few notes on “development” opportunities for Gulden. She had a tendency to be “overly transparent,” according to the review. And she should work on not “overplaying courage of conviction.”

Rosero’s frustrations were growing — Exxon’s carbon-capture project had begun to seem to him mere window-dressing. In January 2020, he and hundreds of other employees gathered inside an auditorium at Exxon’s gleaming office complex, opened in 2014 and set on a 385-acre campus outside Houston. It was for a regular town hall meeting, the kind where rank-and-file employees get to ask questions of senior executives.

Rosero had alerted one of the panelists — a vice president of geoscience— that he was planning to ask a longer question. She instructed him to keep it very brief.

At the meeting, which didn’t include Gulden’s division, Rosero read from a printout of remarks he’d prepared. He said he believed Exxon was speaking out of “both sides” of its mouth on climate change. Although the company said it was dedicated to reducing emissions, for instance, it was pursuing plans that would boost emissions “by at least 20 percent over the next five years.”

Exxon’s state-of-art campus, just outside Houston, features its iconic Energy Center building, with a 10,000-ton “floating cube” that appears to hover over a plaza below. Getty Images

Rosero says he spoke for about two minutes in all, concluding by saying Exxon had “a problem of behaviors and leadership.”

The room was silent.

The vice president who’d counseled him to keep his remarks brief did not seem pleased. I don’t hear a question in there, Rosero recalls her cooly replying.

A panelist involved in Exxon’s climate research spoke up, as if to neutralize the tension. The company is aware there is an impact, he said, and we take that into account.

Rosero felt discouraged, but in the months to come focused on his computer modeling work on oil and gas projects in Guyana and Brazil. Soon, the COVID pandemic had swept the country, and many Exxon employees started working remotely.

One day that summer, while working from home, he logged onto a Zoom meeting with his supervisor for his annual review. He’d been told months earlier to expect a strong evaluation.

But to Rosero’s surprise, the supervisor raised the issue of his workplace behavior, citing his long question at the town hall meeting, he recalls. He was told he now ranked in the lowest “needs improvement” category, and presented two options for a way forward. Rosero could enter into a three-month “performance improvement plan” — a PIP, as it’s known, is viewed in many companies as a precursor to being fired. Or, there was a second option: he could quit Exxon and leave with three months’ paid severance.

When the Zoom ended, Rosero walked upstairs to find Gulden. He found her at her desk.

“Guess what my ranking is?” he asked. “They’ve PIPped me.”

“What?” she said.

An Exxon spokesperson declined to explain the reasoning behind Rosero’s poor evaluation to the Globe Magazine. The company has previously defended its evaluation process for all employees as fair, and not vindictive.

Enrique Rosero and Lindsey Gulden at their Newton home in December.Lucy Lu for the Boston Globe

Rosero’s trust in Exxon had been eroding for a long time. He accepted the severance and began his job search. On his last day in July 2020, he sent a goodbye email to dozens of colleagues with the subject line “why i’m quitting exxonmobil,” encouraging them to keep fighting the good fight. “We are, after all, the change we seek.”

Gulden was crushed. It was cruel, she felt, to demote Rosero to such a low ranking, given his reputation for hard work and all he’d brought to the company for years.

The experience also led Gulden to play and replay her own experiences at Exxon, including the previous year’s dispute over the Permian Basin drilling estimates. HR officials had insisted they’d get back to her with the results of their inquiry, she recalls, but nine months had passed. She asked for updates and heard nothing. She was sure her concerns had been brushed off.

She had long been Exxon’s champion in their household, supporting the corporate ethos that all feedback, good or bad, strengthened the company. She’d trusted that Exxon wanted to be part of the “new energy” future.

Now she thought: How could I have been so gullible?

“I believed them,” she says, “all the way up until the minute that they PIPped him.”

On September 13, 2020, The Wall Street Journal published a lengthy article headlined “Exxon Used to be America’s Most Valuable Company. What Happened?” The story took a broad look at the company’s falling fortunes and declining staff morale, and included interviews with 20 former and current employees, some anonymous.

“It has been a stunning fall from grace for Exxon Mobil Corp,” it began. “Just seven years ago, Exxon was the biggest U.S. company by market capitalization. It has since lost roughly 60% of its value, with its market cap now at around $160 billion, after the pandemic crushed demand for fossil fuels.”

The article went on to diagnose the core problem: that Exxon went all in on oil and gas at a time competitors were pivoting to renewables. “Investors are fleeing and workers are grumbling about the direction of a company some see as out of touch and stubborn,” it continued. The energy reporter also cited Rosero’s complaints and goodbye email and, later in the piece, cited “six named and unnamed sources” on the internal controversy over drilling projections in the Permian Basin.

Darren Woods, the CEO of ExxonMobil, speaks at the Milken Institute’s Global Conference in California last May.Apu Gomes/Getty Images

The story wasn’t a surprise to Exxon. The Journal had contacted the press office in advance with questions. Exxon immediately launched an internal investigation to find who anonymously cooperated with the reporter, according to a federal investigative report. Company audit staff combed employee emails and data files, and eventually narrowed their focus to about 10 people. Gulden and Burch were among them.

On October 23, 2020, about five weeks after the Journal story, Gulden got a call on her cellphone. It was an Exxon vice president.

The conversation proved to be short. She was told she no longer aligned with the “values” of ExxonMobil, and that leaders had lost confidence in her commitment to the company. She was being terminated, effective immediately.

When Gulden asked if her firing had something to do with the Journal article, she says, she was told that it did not. (Several months later, Burch was fired as well.)

News of Gulden’s firing traveled fast within Exxon. One scientist who worked alongside her says it was shocking, because Gulden was regarded as “a great team leader.” This scientist, who asked to remain anonymous for fear of professional retaliation, says Gulden’s firing contributed to his own eventual decision to resign.

“It made clear this is a company where speaking up is not being tolerated,” he says.

Even with Gulden gone, Exxon executives would find the Permian Basin data controversy was far from over.

In January 2021, the Journal reported that the SEC had been investigating Exxon after receiving a complaint about exaggerated drilling projections. The news caused a temporary plunge in its stock prices.

That same month, lawyers filed a class-action shareholder lawsuit against Exxon in Texas, alleging the value of the Permian Basin holdings were knowingly exaggerated by top executives on the order of $10 billion or more. One of New York’s top securities-fraud law firms would be handling the case.

At first, Gulden thought she should just move on. Consider the Exxon chapter of her life over. By the start of 2021, she and Rosero were preparing to move to Massachusetts. He’d found a new job as a senior scientist at a Boston-based risk management company, and she was hired as a data scientist at a health care company.

But she feared repeating what she saw as a troubling pattern in her way of thinking — blocking out negative information she didn’t want to confront. She realized that some of the good things about working at Exxon had blinded her. “I totally fooled myself,” she says. “It was my own selfish refusal to see the truth. I didn’t want to upend my life.”

As she considered what to do, she also thought a lot about her late father, Wynne “Chip” Gulden, a perennially upbeat man who had long espoused the virtues of American industry. For years he was an executive at Cummins, one of the nation’s largest engine makers, headquartered in her hometown. But her father put something else in life first, as his obituary pointed out: “One’s integrity is his only possession of true value.”

Gulden reached out to a lawyer.

On February 10, 2021, Gulden and Burch filed a securities-fraud whistleblower complaint against Exxon, saying they were fired in retaliation for complaining about inflated drilling figures in the Permian Basin. They filed their action with the Occupational Safety and Health Administration, or OSHA, in the US Department of Labor, which handles such complaints.

It was a big risk: Such cases rarely work out for former employees. A review of federal data shows that from fiscal years 2021 to 2023, about 330 whistleblower complaints related to securities fraud were filed. Only five of them — or 1.5 percent — were found to have merit or probable cause.

For the next year and a half, Gulden regularly spent hours a week gathering information for the lawyers. Exxon pushed back every step of the way, telling federal OSHA investigators the firings had nothing to do with the substance of Gulden and Burch’s internal complaints. “Gulden’s termination had absolutely nothing to do with any complaint of fraud,” an Exxon spokeswoman tells the Globe Magazine.

Instead, the company told investigators the pair violated company policies by mishandling and delivering sensitive internal information to the media — in other words, alleging they leaked sensitive information to the Journal.

There apparently wasn’t any concrete evidence that Gulden and Burch were sources, according to the investigative report. Instead, Exxon officials later cited evidence that Burch had transferred some work files to his personal computer, and records of Gulden’s email included some disparaging references to the company, as well as signs she was looking for a new job.

One Exxon executive told OSHA that the company’s audit team believed that “since Dr. Gulden’s husband was quoted in the article she was ‘guilty’ by association and probably assisted in the WSJ article,” according to the report.

When asked about the Journal, Gulden told an OSHA investigator she was called by the reporter. He presented some information he’d already heard from others about the data controversy, and she confirmed it, a court record shows. Burch says he was contacted by the reporter, but referred the inquiry to Exxon’s media office.

By the fall of 2022, Gulden and Burch received good news: Federal investigators ruled in their favor, finding there was “reasonable cause” to believe Exxon violated the whistleblower statute. In October 2022, they released an 11-page report describing Gulden and Burch as “illegally retaliated against” and unfairly professionally damaged. It noted that neither of them “had any disciplinary history and both had exemplary work records.”

“ExxonMobil’s actions are unacceptable,” wrote Assistant Secretary for Occupational Safety and Health Doug Parker, in a press release. “The integrity of the U.S. financial system relies on companies to report their financial condition and assets accurately.”

The ruling also said that even if Gulden and Burch were among those who spoke to the reporter, that would have been “protected activity” under the statute.

The decision also said Gulden and Burch were immediately owed back their jobs, back pay, and damages. In Gulden’s case, that included back wages of about $240,000, some $21,000 in moving expenses, and $50,000 in damages.

Exxon’s lawyers have challenged the ruling, and argued they don’t have to pay anything during the appeal — even as OSHA insisted that they do. Gulden’s and Burch’s efforts to force Exxon to comply have been entangled in complex litigation for the past two years, but to no avail. They’ve since focused on a different approach, filing a separate wrongful termination lawsuit in federal court in New Jersey. A trial date has not been set.

Their attorney, Neil Henrichsen, says companies such as Exxon hope these stretched-out cases will deplete the will of former employees. But there’s so far little evidence that will happen with Gulden and Burch. “They are dedicated to justice in this case,” Henrichsen says.

Lindsey Gulden at a 2024 whistleblower event in Washington, D.C.from the national whistleblower center

Gulden was asked to speak at National Whistleblower Day last July in a Senate hearing room on Capitol Hill. Her closest childhood friend, Sylvia Chambers, now a lawyer in Indianapolis, tuned in to watch on C-SPAN.

Standing behind a microphone in the Kennedy Senate Caucus Room, Gulden fought to tamp down her nerves about public speaking.

“ExxonMobil has continued to pursue what I would describe as a strategy of delay of justice in order to ensure denial of justice,” she told the gathering, summoning a steady voice. “But we’re patient. We’ll continue to press the case for as long as it takes.”

That was the Gulden that Chambers knew, willing to stand up for what she believed in. You go girl, she thought.

Gulden’s confrontation with Exxon over the last several years stems from calculations aimed at predicting the future: Would Exxon be able to squeeze a million oil-equivalent barrels a day from the Permian Basin in 2024? As it turns out, state-level government databases show Exxon didn’t nearly reach that number.

In 2024, Exxon extracted about 600,000 barrels a day — the amount Gulden and others maintained all along was more realistic.

When asked about the 2024 drilling results, an Exxon spokesperson did not dispute the production numbers. But she suggested they do not undermine the company’s original projections, and the lower production was an intentional choice based on supply and demand. “Energy markets are dynamic, and their prices can affect production plans,” she wrote in an email.

Gulden is scheduled to be deposed in May for a shareholder suit against ExxonMobil.Jason Paige Smith for The Boston Globe

Gulden says she should feel vindicated by that 600,000 number, but she instead feels “mostly sad to be right.”

She and Rosero are trying to move on with their lives in Newton, enjoying involvement with local school groups and their daughter’s activities. They now run full-time consulting practices, primarily working for organizations dedicated to reducing global warming.

Gulden’s name still figures prominently in the files of Exxon’s legal staff. Though the SEC concluded its probe without taking any enforcement action, Exxon still faces Gulden and Burch’s wrongful termination lawsuit in New Jersey, and the class-action shareholder lawsuit in Texas, which now includes as plaintiffs the State of Rhode Island (on behalf of its retirement fund) and Amalgamated Bank. Gulden is set to be deposed in May for the shareholder suit.

Amid all of it, Gulden maintains she’s still an optimist, mostly. She’s working with members of Green Newton, a local climate-action group, on a project that aims to convert all homes along her residential street to electric energy. If successful, it would forgo the need to replace aging gas pipes underground.

It is a far smaller effort than trying to get the likes of Exxon to do more to stop global warming. But she often thinks of the motto emblazoned on the sweat shirts of her high school cross-country team: “Do what you can, with what you have, where you are.”

Patricia Wen can be reached at patricia.wen@globe.com. Follow her @GlobePatty.