Despite the controversy on Capitol Hill swirling around the Keystone XL pipeline and a vocal grass-roots movement against the project, half of Americans have never even heard of the pipeline, a recent poll found.

The project, which would transport heavy crude oil from Canada's oil sands region to refineries on the U.S. Gulf Coast, has been met with a flurry of criticism from some groups and strong support from others. While proponents say Keystone is an economic godsend, critics say it's a recipe for environmental disaster.

[READ: Keystone XL Bill Heads to House Vote But Is Largely Symbolic]

Still, just 3 percent of Americans surveyed by the Yale Project on Climate Change Communication say they're "very closely" following the progress of the pipeline's approval, which has been in limbo for several years as the Obama administration investigates the project's environmental and public interest impact.

Among those who have heard of the Keystone XL pipeline, the vast majority – 63 percent – support the project, with almost 30 percent saying they "strongly support" it, while just 15 percent say they "strongly oppose" the project.

But even with the solid support for the fossil fuel-based Keystone XL pipeline among survey participants, almost 90 percent of those surveyed said Congress and the White House should still make clean energy a "very high" (26 percent), "high" (32 percent) or "medium" priority (28 percent), according to the Yale study.

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Similarly, 70 percent of Americans say global warming and climate change should be a very high, high or medium priority for the legislative and executive bodies, with 84 percent supporting an effort to reduce the effects of global warming, even if there are economic costs.

But despite the high readings, public support for several climate and energy policies has actually declined since the group started collecting data in 2008. While a majority is still for policies such as expanding offshore drilling and regulating carbon dioxide as a pollutant, support has waned. Support for funding research of renewable energy sources is down 21 percentage points since 2008, for example, while support for consumer tax rebates for energy-efficient vehicles or solar panels dropped 15 points.

