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Paul Barys stood in front of a TV camera. Behind him, a green screen tracked ominous weather patterns.

Five-day weather forecasts were largely unpredictable at the time, but the lean, bearded meteorologist knew something major was about to happen.

It was 1993, and he'd been in the city for just eight years. His bosses were giving him the leeway afforded a veteran of nearly a decade, but he hadn't fully built the trust and credibility a 30-year career would later bring.

But he stood there that night about to make a bold claim — one that, if he was wrong, could cost him that trust and derail his career.

"It's going to be the worst storm in the history of Chattanooga," he told viewers that March night.

His news manager was furious.

"'Why did you say that?' he told Barys. 'You're sticking your neck way out. You're going to get it chopped off; you're going to look like an idiot.'"

The next night, the snow came. More than 18 inches fell across the region. To date, it's the city's worst snowstorm in history.

"No one ever said anything after that," he said.

A NEW ENVIRONMENT

Twenty-six years have passed, and in that time, Barys has become arguably the most recognized weather forecaster in the Chattanooga area.

He still reports to the same building at WRCB-TV. But now he's the station's chief meteorologist.

His in-studio office is surrounded by monitors showing the latest weather reports. He compiles the information into short made-for-TV segments to get viewers across the Tennessee Valley the weather information that's most important to them. News anchors and the company's social media channels often cite "Paul says" in their reports, letting viewers know what's about to be said can be trusted.

Over the years, weather forecasting has vastly improved. Radar systems are newer and weather stations are more sophisticated, leading to more accurate long-term and short-term weather predictions.

But, over those 30 years, the weather Barys reports also has changed.

There are more warm nights and fewer cold days. Average temperatures have risen and continue to rise.

Scientists say with certainty that's due to climate change caused by the burning of fossil fuels. However, Barys disagrees.

He subtly takes jabs at that scientific consensus — sometimes on air, verbalizing his theory on why the climate is changing. It's a theory he believes is more logical than a human-impact caused mainly by the burning of fossil fuels: "I believe in cycles. That's what I believe in. I believe in cycles. We are, right now, at this very second, in a warming cycle."

The cycle is natural and overstated, Barys says. Any man-made effects are caused by aircraft contrails, urban heat islands and misplaced thermometers, he explained. The overblown concerns can be accredited to the 24-hour news cycle and over-coverage by CNN, which is just looking to fill time, he argues.

"People like to worry," he said. "People want to have something, a boogeyman, out there."

THE SCIENCE

Marshall Shepherd, director of the University of Georgia's Atmospheric Sciences Program, is an acclaimed climate expert.

Aside from his role at UGA, he is the host of The Weather Channel's "Weather Geeks" talk show and chairman of the NASA Earth Sciences Advisory Committee. He's also been president of the American Meteorological Society and has received a long list of awards.

He says the discussion around climate change begins with the understanding that carbon dioxide is increasing.

That isn't debatable, he said.

In fact, everyone interviewed for this article — on both sides of the argument — agrees with that and the fact that the Earth's temperature is warming.

"If you look at the period after 1850, when we figured out how to burn fossil fuels and the Industrial Revolution, we're well outside that natural bound [of carbon levels] that never got above 290-300 parts per million. We're well above 400 now," Shepherd said. "So anybody who says the carbon dioxide is not increasing, I walk away from them immediately because I know that they're just stuck in ideological La La Land."

So the question becomes: how are scientists so certain those rising carbon levels are caused by humans and leading to rising temperatures?

For that, Vanderbilt environmental policy and global change expert Jonathan Gilligan gives an overview to his students and others about the scientific consensus after examining decades of research.

Gilligan specializes in environmental policy, risk management, atmospheric science and global climate change. He co-wrote "Beyond Politics: The Private Governance Response to Climate Change" with Michael P. Vandenbergh, a scholar in environmental and energy law and the distinguished chair of law director at Vanderbilt. Gilligan combines years of studies, journals and reports. He also regularly talks to climate scientists through academic work and at national and international conferences. From there, he discusses trends and agreement he sees across each report.

There are two key factors in beginning the correlation between rising carbon levels and increasing temperatures, he said.

Scientists know through study that oxygen in the atmosphere is decreasing while carbon dioxide is increasing.

Secondly, scientists are able to study isotopes — variants of a particular chemical element. Those isotopes show where a molecule comes from.

Scientists say both factors show them that carbon dioxide levels are rising due to an increase in the burning of organic material.

"So we're looking at where is there in the world where somebody — people or nature or anything — where billions of tons every year of organic material is being burned," Gilligan said. "At that point, you have ruled out everything except fossil fuels. Then, if we look at the rise in carbon dioxide, it almost exactly parallels the rise in fossil fuels consumption."

From there, scientists look at whether that human-caused rise in carbon dioxide is causing the global climate trends they're seeing.

For that, scientists look at models, 50 years of climate records and climate change throughout history.

Many of those early reports five decades ago showed the climate was warming, but scientists didn't know why.

By 1995, computer models were advancing. These days, modern technology continues to make the models more reliable and accurate, according to Gilligan, Shepherd and others.

Early models tested nearly every theory to find what could be causing the changing temperatures: volcanoes, sunspots, fossil fuel burning, etc., Gilligan said.

The theories on what scientists could expect to see if climate change was being caused by fossil fuels have played out nearly exactly. The others have not, they added.

The models predicted if greenhouse gases were the culprit, the lower atmosphere would warm while the upper atmosphere in the stratosphere would cool. That's exactly what scientists have seen play out for 50 years. Modern models have confirmed those findings.

"That was a prediction made in 1967. We now have more than 50 years of data after that," Gilligan said. "There are a lot of these different patterns."

There have been other cycles of climate change throughout history, as well: prolonged heat waves causing widespread drought and cold stretches that produced ice ages. In each instance, the earth's carbon levels also have changed.

"Natural changes in carbon dioxide produced very large changes in temperature," Gilligan said.

Climate scientists and skeptics, like Barys, both agree the cycles exist — the question is who or what is causing the current cycle. Climate scientists worry we are in the midst of another drastic temperature change, one that has not been caused naturally and could have been prevented.

There is virtually no doubt among scientists that increasing carbon levels are being caused by the burning of fossil fuels, meaning, they say, this period of global warming has certainly been caused by humans.

A NASA finding said 97 percent or more of climate scientists agree on the issue. And nearly all of the world's leading science organizations have released public statements expressing their agreement with the scientific consensus.

It's an issue U.S government officials from more than a dozen agencies believe will impact the country's health and economy gravely, increasing the likelihood of wildfires and impacting crops, among a litany of other concerns, according to the 2018 National Climate Assessment.

The Trump administration released the report, which said humans are the main cause of climate change and found the financial repercussions will be devastating. The president was quick to question the findings of the 1,600-plus-page report, conducted by 13 of his government agencies as well as university scholars, climate scientists and other experts.

"The [National Climate Assessment] report is very useful because it's mandated by Congress to assess the climate," Shepherd said. "That's very important; even if the current administration has a different viewpoint, thankfully, it's mandated by law that we have to do it."

IS IT JUST A NORMAL CYCLE?

On a recent rainy afternoon, Barys repeatedly pointed to the work of John Christy.

"He's very, very good. Very, very good. The man is very, very intelligent," Barys said.

Christy is a professor of atmospheric science at the University of Alabama in Huntsville, where he began in 1987 as a formal climate scientist. He was added to the Environmental Protection Agency's Scientific Advisory Board under President Donald Trump earlier this year.

Christy was widely criticized after an error in a climate report he published in the early 2000s identified atmospheric cooling, rather than warming. Other scientists quickly found errors in the research, which Christy since has acknowledged. He ultimately conceded the earth was not cooling, but is indeed warming.

However, he maintains climate concerns are overblown and believes climate models are largely unusable because they have previously overstated global warming trends.

He is skeptical climate change is caused primarily by people and disagrees with the scientific consensus presented by Gilligan and others.

"I don't know who this Dr. Gilligan is," Christy said. "Not evidently someone who is really a climate scientist. At least, I've never heard of him, but I would be interested to know how he can say humans have caused most of the warming. He has no evidence for that. That's what we specifically do. I am a real climate scientist."

Of the NASA statistics, he calls them "bogus."

Christy believes the carbon dioxide humans have put in the air have caused some changes, but that those changes are overblown. He doesn't rule out the theory that the changes are mostly natural and believes the current cycle of climate change is "modest."

Barys explains the changes through several outlying factors — although many are still human-caused. There is some truth to those concerns, Gilligan said.

Thermometers are sometimes put in the wrong locations and pick up extra heat because they are near parking lots.

The urban heat island — the process of warming surface temperatures in big cities due to large concentrations of blacktop and concrete, deforestation and land-use practices — is real.

Contrails can change daytime temperatures by reflecting sunlight away and affect nighttime temperatures by absorbing heat rising from the surface. This was indeed, as Barys said, proven after the 9/11 terror attacks when scientists were able to study the atmosphere after all air traffic had landed been grounded.

"Scientists have known about this for a long time and have been dealing with that, though," Gilligan said. "We have made corrections and adjustments. The urban heat island is very real, but the places where we see the biggest warming are Siberia, Canada, Greenland — places that aren't big cities with lots of asphalt."

Christy's work remains popular on some internet sites and even on Capitol Hill, where he is regularly cited and called upon by some Republican lawmakers skeptical of the scientific consensus.

He is among the fraction of scientists whose research doesn't match the findings of the vast majority of scientists.

"John Christie, and there are a few other names, we know who they are," Shepherd said. "They do science, and I'm not poo-pooing on them as scientists, but I guess the point is, I've always been baffled by people who give credence to 3 percent and not 97 percent. The answer is it's confirmation bias."

SKEPTICISM AND FAITH

Barys and Christie aren't alone in their thinking despite disagreeing with most scientists and, according to Shepherd, meteorologists.

Residents in Tennessee and across the Appalachian region disagree that climate change exists or is caused by humans at a higher rate than anywhere else in the U.S., according to a Yale and George Mason University climate 2018 study.

Between 40% and 50% of residents in the majority of counties in Tennessee, Kentucky, West Virginia and Ohio either entirely don't agree that climate change is happening or are unsure. Those who do agree it is taking place often hold a similar view to Barys: that the concern is overblown, the change isn't caused by the burning of fossil fuels and is part of a cycle that will ultimately readjust even without human changes.

However, nationwide, 70% of Americans believe global warming is happening, compared to 14% who do not and 16% who were unsure. Fifty-seven percent believe global warming is caused mostly by human activities, compared to 32% who responded it is caused by natural changes.

The report's authors say there are some potential explanations for the widespread doubt in Appalachia.

For starters, studies have shown the Appalachian region is an area where warming has been less severe than other parts of the world, said Jennifer Marlon, a Yale Program on Climate Change Communication research scientist who worked on the project.

The other explanation: it's political.

"It's true, and a lot of environmental issues tend to be more left-leaning — a bigger concern for liberals," she said.

Although studies show that most Americans — regardless of political affiliation — want clean air, clean water and conservation, admitting climate change is happening and is caused mainly by human interference brings larger implications, Marlon argues.

It means heading down a path toward more regulations and bringing more government intervention to the lives of residents who are trying to avoid just that.

"They don't like the solution, so they don't want to admit [climate change is] happening," she said.

But there are also deeper ties dealing with how culture and religion overlap with those political views, Katharine Hayhoe argues.

Hayhoe is a climate scientist and the director of the Climate Science Center at Texas Tech University. She is also the wife of a pastor and an evangelical Christian who staunchly argues man-made climate change is a proven scientific fact with decades of supporting research and data.

The couple co-wrote a book about 10 years ago, "A Climate for Change: Global Warming Facts for Faith-Based Decisions," after receiving a flood of questions about how people of faith should deal with the changing climate.

Since then, Hayhoe has spoken regularly to churches and other groups on the topic of religion and climate. She hosts regular climate discussions on her YouTube channel, the most popular of which is "What does the Bible say about climate change?"

"When people ask me if I believe in climate change, my answer is 'No, I don't believe it.' It is being deliberately framed as an alternate religion. And any good Christian knows what to do if you're presented with an alternate religion: that's a false prophet, you reject it," she said.

The word "believe" is key for people of faith. There are those who frame climate change as an earth-worshiping religion when it should be presented as scientific fact with years of evidence that can be measured and tested, she said.

People of faith began to reject the findings because of that framing, and climate change denial quickly became part of a package of core beliefs for Christian conservatives, she said — along with opposing immigration, being pro-life, always supporting the candidate of the party and more.

"It's an entire political package now to the point that so many people's statement of faith is being written first by their politics and only a very distant second by the Bible," she said. "If the two come into conflict, they'll go with their politics over what the Bible says. That is a huge problem as a Christian."

Contact staff writer Mark Pace at mpace@timesfreepress.com or 423-757-6659. Follow him on Twitter @themarkpace and on Facebook at ChattanoogaOutdoorsTFP.

This article was updated April 16 to further clarify Hayhoe's stance on climate change.