If you're trying to wrap your head around climate change, don't consult Donald Trump.
"I am not a believer," the Republican presidential candidate said on a radio show in September. "Unless somebody can prove something to me, I believe there’s weather."
Sadly, Trump isn't alone. Even as world leaders prepare to convene in Paris later this month for the U.N. Framework Convention on Climate Change with the goal of reaching a new agreement for reducing carbon emissions, a vocal minority of policymakers continue to deny that the problem even exists.
Although 97 percent of climate scientists insist climate change is real and caused by human actions, 56 percent of Republicans in Congress deny these atmospheric changes, according to Think Progress. Some conservative commentators have gone so far as to describe climate change as a "hoax."
Yet the facts are undeniable. Sea levels and global temperatures are rising (this year is on track to become the hottest on record), glaciers are melting, and ice sheets are shrinking at unprecedented rates. CO2 levels have also shot up dramatically since the Industrial Revolution -- suggesting these events are very likely a product of human activities.
"Scientific evidence for warming of the climate system is unequivocal," the Intergovernmental Panel on Climate Change has declared.
How is it possible to deny this overwhelming evidence that global warming is real and humans contribute to it?
For starters, many leaders and corporations -- such as ExxonMobile -- have a strong financial incentive to ignore the facts. But there are many other subtle reasons why people might turn a blind eye to research. Here's what social scientists have to say about the psychology of climate change deniers.
They seek out information that confirms their beliefs -- and ignore anything that challenges them.
At the core of climate change denial is the brain's confirmation bias -- a natural tendency to seek and interpret facts in a way that confirms our pre-existing beliefs.
"Nobody wants to be wrong, and that elicits confirmation bias, which is when we seek out information that confirms that we believe to be true," said Dr. Robert Gifford, an environmental psychologist at the University of Victoria.
In looking for confirmation, we're trying to avoid what's known as cognitive dissonance, which is the uncomfortable state of having inconsistent thoughts or beliefs. If these inconsistencies suggest we should change our behavior, then we will typically change our beliefs to regain a sense of harmony rather than change our behavior.
For instance, if a business leader has a vested financial interest in fossil fuels, there's a good chance he won't want to acknowledge the threat of climate change, because doing so would force him to address some uncomfortable questions about how he might be contributing to environmental destruction.
Dissonance, then, creates tension. Usually, the person will seek to reduce that tension in the easiest way possible -- which, in this case, usually means finding a way to believe that climate change isn't real or isn't a big deal.
Confirmation bias ultimately turns into "motivated reasoning," an emotion-based decision-making process in which people to cling to false beliefs and ignore any opposing evidence.
They don't trust scientists, and listen instead to high-profile skeptics.
Add to this equation a distrust of experts and scientists (a psychological phenomenon known as "discredence"), and you've got a recipe for denial.
Climate change denial hit a six-year high in 2014, with 23 percent of Americans saying they do not believe in global warming, and 53 percent saying they do not believe global warming is human-caused.
This is likely due, in large part, to the influence of high-profile climate skeptics.
"Social scientists have documented that the public follows 'elite cues' when forming opinions on topics, especially those for which they don't have a lot of information," Dr. Riley Dunlap, an environmental sociologist at Oklahoma State University, told The Huffington Post in an email. "So when Republican politicians and pundits, whose voices are amplified by conservative media figures, deny climate change, this readily filters down to party activists and eventually many lay Republicans."
These media messages have a major impact. In a forthcoming study, researchers tested the influence of climate change denial messages on American adults' views of climate change, and found that they have an especially strong effect on conservatives.
"A single exposure to a denial message significantly reduces subjects' belief in and concern about climate change," said Dr. Aaron McCright, an environmental sociologist at Michigan State University and the study's lead author.
Dunlap, McCright and Gifford all said mistrust of scientists is a growing issue -- and for people who don't trust scientists, scientific evidence clearly doesn't carry much weight.
"Data reveals a huge and growing gulf between what scientists and the public think about vaccines, animal research, genetically modified food, climate change and more," he wrote.
They get stuck in "echo chambers."
Holding certain ideological views -- such as religious fundamentalism or conservatism -- makes it more likely that a person will deny climate change, and their denial can be reinforced by others within their social network with similar beliefs.
Denial is a social phenomenon, according to Renee Lertzman, a psychosocial researcher whose work focuses on promoting action on climate change in organizational settings.
"In order for me to be in denial, I kind of need others to participate in that," she said. "So we need to recognize that so much of what we’re looking at is a social process, not an individual issue."
It’s easy for people to expose themselves only to beliefs that reinforce their own through media exposure and their own social networks, which may reinforce their views while shielding them from dissenters. This is also known as the "echo chamber" effect.
"The conservative echo chamber -- Fox News, talk radio, conservative columnists and bloggers -- combine to create a 'bubble' in which many committed Republicans live, and when it comes to scientific issues we find that they literally create an 'alternative reality' in which human-caused climate change is a hoax," Dunlap said. "The problem is that this conservative worldview is deeply at odds with empirical reality."
So does the science suggest any ways of combatting denial?
"In the short term, absolutely not," McCright said.
These experts agree that the best step forward may be to rally those who do understand the issue around potential solutions. After all, McCright said, the debate has never really been about the science.
"It would be far more productive for all of us if we would have a national discussion about these differing belief systems, identifying where we disagree but, more importantly, identifying where we agree, and then try to govern in ways that effectively solve the problems we collectively face," he said.
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