The release of hard-hitting documentaries such as “An Inconvenient Truth,” the impact of national disasters such as Hurricane Katrina and the media’s emphasis on climate change, among other factors, may be affecting Americans’ opinions of global warming, a new study reveals.

A recent study conducted by the Yale School of Forestry and Environmental Studies, in collaboration with Gallup and the ClearVision Institute, shows that 71 percent of Americans are now convinced global warming is real, and the percentage who say it is currently having, or will soon have, a negative impact has risen 20 points since 2004.

“[The study] shows a significant shift in Americans’ perceptions in just three years,” said Anthony Leiserowitz, the study’s principal investigator and the director of the Yale Project on Climate Change. “One of the most surprising findings was that Americans increasingly recognize the urgency of global warming.”

The study found not only that there has been a shift in opinion, he said, but also that Americans say they are committed to taking drastic preventive action.

For instance, 68 percent of respondents said they favor passing a protocol that would require the United States to reduce its carbon emissions by 90 percent by the year 2050 — regulations that far surpass those laid out in the Kyoto Protocol that many European and Asian countries have adopted. The Kyoto Protocol is an international treaty that would require the United States to reduce emissions by 7 percent over the next five years, but the United States has so far declined to sign on, Leiserowitz said.

In addition, the survey found, 85 percent of Americans support increasing the fuel-economy standard for vehicles, even if car prices were to rise by up to $500, and 82 percent would pay an average of an extra $100 per household to support legislation requiring 20 percent of household utilities to produce electricity from renewable sources.

“It’s definitely inspiring that there’s a growing community conscience [about global warming] and that the public is willing to make personal sacrifices in their income to change the situation,” said Kate Gasner ’09, a coordinator for the Student Taskforce for Environmental Partnership, a campus group that works on environmental issues. “The money statistic really makes that concrete.”

But she added that while the survey represents an encouraging first step, the real challenge lies in translating opinion into action.

“In STEP, for example, we see lots of people receptive to our message, but when it comes to something like getting residential colleges to conserve energy, fewer change their daily habits,” Gasner said. “It’s difficult to align people’s practices with their opinions.”

The study found that respondents were not enthusiastic about energy-conservation policies across the board, however. In fact, the majority opposed higher carbon taxes, such as those on gasoline and electricity, even though more than half said they attributed climate change to human activities such as fossil-fuel use.

Leiserowitz said that part of the challenge lies in showing citizens the importance of making short-term decisions that are long-term investments, despite the frustration of not seeing immediate effects.

“Fossil fuel, coal, oil and gas underlie almost everything we do in modern civilization,” he said. “To move those energy foundations to non-carbon sources is going to be a big effort. Right now, we’re in a critical window of turning around a super tanker — and it takes a long time to turn around a super tanker.”

The study also revealed that Americans believe climate change will inform the upcoming presidential election: 40 percent said a presidential candidate’s position on the issue will strongly influence how they vote.

But many Yalies said they are skeptical about whether this statistic will hold true in the election.

“There’s always a marked discrepancy between the way people answer questionnaires and the way they behave,” Antonio Ingram ’11, who is interested in environmental activism, said. “In the abstract, everyone is for the environment. But this is not always reflected in the political leaders they choose to elect.”

David Kohn ’10, an environmental engineering major, said the survey’s findings do not line up with government policies, which he said may be detrimental to America’s long-term economic prospects. He said that the 40 percent statistic suggests that presidential candidates should propose bold environmental solutions, but that this has been far from the case.

Global warming, Leiserowitz said, tends to take a backseat to other national issues — such as the Iraq War — in the minds of most citizens. The survey showed that citizens see it as a distant phenomenon, primarily affecting other people, species and places, he said.

“We see a shift in opinions about the time-wise immediacy of climate change, but not about its spatial immediacy,” Leiserowitz said. “Many people still see it as a phenomenon affecting small island countries.”

Despite this perception, it seems Americans are optimistic about their role in affecting change: 82 percent said they agree they can personally take action to reduce the effects of climate change.

While it is clear immediate action is needed, Leiserowitz said, climate change experts still stand divided on the most effective solutions that individuals and countries should pursue. The focus in the climate-change conversation, he said, has seen a shift from describing the phenomenon to exploring potential solutions at the individual, local and national levels.

“The actual changes we have to make are going to be hard to conceptualize and realize,” said Christopher Shirley ’10, an environmental studies major and a member of STEP.

He said he believes individual efforts are ineffective unless mirrored by efforts on larger scales.

But as media coverage of the issue continues to grow, those with the power to effect change, such as policy makers, are beginning to see global warming as more urgent, Leiserowitz said.

“Al Gore had an even larger effect that I had thought,” Kohn said. “Scientific knowledge is not always accessible, and [the study makes] me think that initiatives like ‘The Inconvenient Truth’ had a necessary message.”