Why do we still debate climate change?

A farmer and his children plant a field with bean seeds and fertilizer in southern Ethiopia in 2008, a year after severe floods destroyed most of the food crop. Ethiopia is the country 10th most vulnerable to climate change effects, according to a report by Maplecroft.

Manila, capital of the Philippines, is one of the five cities, all in Asia and all projected to be centers of high economic growth, that face "extreme risk" from climate change impacts, according to the report.

Cambodia is among the Southeast and South Asian countries tipped to face an increased risk of severe flooding because of projected changes in seasonal rainfall.

A fisherman sits in a boat on the shore of Lake Kivu in Goma in August. "There are no big fish because of the gas; we only catch small whitebait," one said of the carbon dioxide and methane that saturate the lake.

Floodwaters course through Odo Ona in Nigeria's Oyo State in 2011. At least 102 people were killed when a dam burst during torrential rain.

Tainted water pours into a containment pond in a Unity field processing facility in what is now South Sudan, where there are concerns about the environmental damage being caused by the oil industry.

Residents of Jacmel, Haiti, make their way through floodwaters as Tropical Storm Isaac dumps heavy rains in August 2012. An extreme exposure to climate-related events, combined with poor health care access, weak infrastructure, high levels of poverty and an over-reliance on agriculture have led to the country being categorized as at "extreme" risk.

Felled trees lie on the mountainside just outside Freetown. African countries account for 14 of the 20 most at-risk nations.

Residents walk past the Parliament in Bissau, capital of Guinea-Bissau. African countries rank as at high risk in the index, partly due to their natural susceptibility to events such as floods, droughts, fires, storms or landslides. But their high ranking is also a product of the vulnerability of the population and the inadequacies of existing infrastructure to adapt to or tackle climate change challenges because of weak economies, governance, education and health care.

Bangladeshis attempt to stay dry above flood waters in the capital, Dhaka. Bangladesh was ranked the country most vulnerable to climate change, and Dhaka the world's most vulnerable city, due to its exposure to threats such as flooding, storm surge, cyclones and landslides, its susceptible population and weak institutional capacity to address the problem.

• 97% of scientists say humans are causing climate change


• Carol Costello: Why pretend that there's still a debate going on?


• Politicians, conservative organizations seek to foster denial of the reality, she says


• Costello: Lack of trust in scientists is one reason the phony controversy continues

Editor's note: Carol Costello anchors the 9 to 11 a.m. ET edition of CNN's "Newsroom" each weekday.

(CNN) -- There is no debate.

Climate change is real. And, yes, we are, in part, to blame.

There is a 97% consensus among scientific experts that humans are causing global warming. Ninety-seven percent!

Yet some very vocal Americans continue to debate what is surely fact.

The question is, why?

Trust certainly plays a part.

According to Gordon Gauchat, an associate professor of sociology from the University of Wisconsin, just 42% of adults in the U.S. have a great deal of confidence (PDF) in the scientific community.

It's easy to understand why. Most Americans can't even name a living scientist. I suspect the closest many Americans get to a living, breathing scientist is the fictional Dr. Sheldon Cooper from CBS's sitcom "The Big Bang Theory." Sheldon is brilliant, condescending and narcissistic. Whose trust would he inspire?

Cruz: Data doesn't back global warming

Expert: Sea levels make flooding worse

Gingrich: Secretary Kerry is delusional

Nye to Ham: God's not in climate change

But trust isn't the only factor in why many Americans doubt climate change.

I asked Anthony Leiserowitz, the director of the Yale Project on Climate Change Communication. His group has been studying the "why" question for more than a decade.

"We've found there are six very (specific) categories that respond to this issue in different ways," he said.

He calls these categories "Global Warming's Six Americas."

Opinion: Obama's efforts on climate may not be enough

The first group, "The Alarmed," is made up 16% of the public. They believe climate change is an urgent problem but have no clear idea of how to fix it.

The second group (27%) is "The Concerned." They believe climate change is a problem but think it's more about polar bears and tiny islands than a problem that directly affects them.

The third group, "The Cautious" (23%), are people on the fence. They haven't made up their minds whether global warming is real or if it's a man-made problem.

The fourth group, "The Disengaged" (5%), doesn't know anything about climate change.

The fifth group, "The Doubtful" (12%), do not think climate change is man-made. They think it's natural and poses no long-term risk.

Leiserowitz says it's the sixth group, "The Dismissives," that is the most problematic, even though it comprises just 15% of the public.

"They say it's a hoax, scientists are making up data, it's a U.N. conspiracy (or) Al Gore and his friends want to get rich." Leiserowitz goes on to say, "It's a really loud 15%. ... (It's a) pretty well-organized 15%."

And thanks to the media and the political stage, that vocal minority is mighty.

Former presidential candidate Rick Santorum told Glenn Beck on Fox News in 2011, "There is no such thing as global warming." Santorum went on to tell Rush Limbaugh, "It's just an excuse for more government control of your life, and I've never been for any scheme or even accepted the junk science behind the whole narrative."

And just last week, tea party favorite Sen. Ted Cruz told CNN's Dana Bash, "Climate change, as they have defined it, can never be disproved, because whether it gets hotter or whether it gets colder, whatever happens, they'll say, well, it's changing, so it proves our theory."

Meanwhile, the climate change "counter movement" has been helped along by an infusion of cash from, among others, some in the powerful fossil fuel industry.

A recent study by Drexel University found that conservative foundations and others have bankrolled climate denial to the tune of $558 million between 2003 and 2010.

"Money amplifies certain voices above others and, in effect, gives them a megaphone in the public square. Powerful funders are supporting the campaign to deny scientific findings about global warming and raise public doubts about the roots and remedies of this massive global threat," writes environmental scientist Robert J. Brulle, the study's author.

The good news is, those uninformed minority voices are being quieted by nature and by those who have powerful voices.

Extreme weather is forcing people to at least think about how global warming affects them directly. And, perhaps more important, many religious leaders, including evangelicals, are now "green." They concur with the scientific community and take it a step farther. They say we have a moral obligation to save the planet.

Even the enormously popular Pope Francis may soon speak out on global warming. The Vatican press office says Francis is working on draft text on ecology. That text could turn into an encyclical, or a letter to bishops around the world, instructing that the "faithful must respect the environment."

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The opinions expressed in this commentary are solely those of Carol Costello.