Tempers are rising in America, along with the temperatures.
Two decades ago, the issue of climate change wasn't as contentious. The leading U.S. Senate proponent of taking action on global warming was Republican John McCain. George W. Bush wasn't as zealous on the issue as his Democratic opponent for president in 2000, Al Gore, but he, too, talked of regulating carbon dioxide.
Then the Earth got even hotter, repeatedly breaking temperature records. But instead of drawing closer together, politicians polarized.
Democrats (and scientists) became more convinced that global warming was a real, man-made threat. But Republicans and Tea Party activists became more convinced that it was — to quote the repeated tweets of presidential nominee Donald Trump — a “hoax.”
FILE - President George W. Bush waves as he is followed by members of his cabinet after he spoke on global warming in the Rose Garden of the White House, June 11, 2001. Two decades ago, the leading U.S. Senate proponent of taking action on global warming was Republican John McCain. Bush wasn't as zealous on the issue as his Democratic opponent for president in 2000, Al Gore, but he, too, talked of regulating carbon dioxide.
When it comes to science, there's more than climate that divides America's leaders and people, such as evolution, vaccination and genetically modified food.
But nothing beats climate change for divisiveness.
“It’s more politically polarizing than abortion,” said Anthony Leiserowitz, director of the Yale Program on Climate Change Communication. “It's more politically polarizing than gay marriage.”
Leiserowitz says his surveys show 17 percent of Americans, the fastest-growing group, are alarmed by climate change and want action now, with another 28 percent concerned but viewing it as a more distant threat. But there's an often-vocal 10 percent who are dismissive, rejecting the concept of warming and the science.
Sometimes dismissiveness and desire for action mix in one family.
Rick and Julie Joyner of Fort Mill, South Carolina, are founders of MorningStar ministries. Most of the people they associate with reject climate change. Their 31-year-old daughter, Anna Jane, is a climate change activist.
As part of a documentary a few years ago, Anna Jane introduced her father to scientists who made the case for climate change. It did not work. He labels himself more skeptical than before.
FILE - Climate change activists carry signs as they march during a protest in downtown Philadelphia a day before the start of the Democratic National Convention, July 24, 2016. Matthew Nisbet, a communications professor at Northeastern University, says the split with science is most visible and strident when it comes to climate change because the nature of the global problem requires communal joint action, and “for conservatives that’s especially difficult to accept.”
“They're both stubborn and equally entrenched in their positions,” said Julie Joyner, who is often in the middle. “It doesn't get ugly too often.”
People in the 1960s “had faith in science, had hope in science. Most people thought science was responsible for improving their daily lives,” said Marcia McNutt, president of the National Academy of Sciences.
Now “we see partisan polarization or ideological polarization,” said Matthew Nisbet, a communications professor at Northeastern University. The split with science is most visible and strident when it comes to climate change because the nature of the global problem requires communal joint action, and “for conservatives that's especially difficult to accept,” Nisbet said.
Climate change is more about tribalism, or who we identify with politically and socially, Nisbet and other experts say. Liberals believe in global warming, conservatives don't.
Dave Woodard, a Clemson University political science professor and GOP consultant, helped South Carolina Republican Bob Inglis run for the U.S. House (successfully) and the Senate (unsuccessfully). They’d meet monthly at Inglis’ home for Bible study, and were in agreement that global warming wasn’t an issue and probably was not real.
After seeing the effects of warming firsthand in Antarctica and Australia’s Great Barrier Reef, Inglis changed his mind — and was overwhelmingly defeated in a GOP primary in 2010. Woodard helped run the campaign that beat him.
“I was seen as crossing to the other side, as helping the Al Gore tribe, and that could not be forgiven,” Inglis said.
FILE - This image provided by the National Weather Service shows temperatures in the continental United States during a heat wave July 22, 2016.
Judy Curry, a Georgia Tech atmospheric scientist and self-described climate gadfly, has experienced ostracism from the other side. She repeatedly clashed with former colleagues after she publicly doubted the extent of global warming and criticized the way mainstream scientists operate. Now she says, no one will even look at her for other jobs in academia.
In 1997, then-Vice President Gore helped broker an international treaty to reduce heat-trapping gases from the burning of coal, oil and gas.
“And at that moment,” said Leiserowitz, “the two parties begin to divide. They begin to split and go further and further and further apart until we reach today's environment where climate change is now one of the most polarized issues in America.”
Consider lobster scientist Diane Cowan in Friendship, Maine, who expresses dismay.
“I am definitely bearing witness to climate change,” Cowan said. “I read about climate change. I knew sea level was rising but I saw it and, until it impacted me directly, I didn't feel it the same way.”
Republican Jodi Crosson, a 55-year-old single mother and production and sales manager in Bexley, Ohio, thinks global warming is a serious problem because she's felt the wrath of extreme weather and rising heat. But to her, it's not quite as big an issue as the economy.
FILE - Scientist Oliver Grah measures the speed of a melt water stream from Sholes Glacier on one of the slopes on Mount Baker in Washington, Aug. 7, 2015. Glaciers on this and other mountains in the North Cascades are thinning and retreating.
Scott Tiller, a 59-year-old underground coal miner in West Virginia, has seen mine after mine close, and says coal is getting a bad rap.
“I think we've been treated unfairly and kind of looked down upon as polluters,” Tiller said. “They say the climate is changing, but are we doing it? Or is it just a natural thing that the Earth does?”
Overwhelmingly, scientists who study the issue say it is man-made and a real problem. Using basic physics and chemistry and computer simulations, scientists have repeatedly calculated that most of the extra warming comes from humans, instead of nature. Dozens of scientific measurements show Earth is warming. Since 1997, the world has warmed by 0.44 degrees (0.25 degrees Celsius).
Repeatedly explaining science and showing data doesn't convince some people to change their core beliefs, experts say. So instead, some climate activists and even scientists try to build bridges to communities that might doubt that the Earth is warming but are not utterly dismissive.
The more people connect on a human level, the more people can “overcome these tribal attitudes,” Anna Jane Joyner said. “We really do have a lot more in common than we think.”