The last time Congress passed major environmental laws, acid rain was destroying lakes and forests, polluted rivers were on fire and smog was choking people in some cities.

The fallout from global warming, while subtle now, could eventually be more dire. That prospect has Democrats pushing legislation that rivals in scope the nation's landmark anti-pollution laws.

Lawmakers this coming week begin hearings on an energy and global warming bill that could revolutionize how the country produces and uses energy. It also could reduce, for the first time, the pollution responsible for heating up the planet.

If Congress balks, the Obama administration has signaled a willingness to use decades-old clean air laws to impose tough new regulations for motor vehicles and many industrial plants to limit their release of climate-changing pollution.

The Environmental Protection Agency on Friday said rising sea levels, increased flooding and more intense heat waves and storms that come with climate change are a threat to public health and safety. The agency predicted that warming will worsen other pollution problems such as smog.

"The EPA concluded that our health and our planet are in danger. Now it is time for Congress to create a clean energy cure," said Rep. Ed Markey, D-Mass., one of the sponsors of the American Clean Energy and Security Act.

If passed, it would be the first major environmental protection law in almost two decades. In addition to attempting to solve a complex environmental problem associated with global warming, the bill also seeks to wean the nation off foreign oil imports and to create a new clean-energy economy.

"It's a big undertaking," said the chairman of the House Energy and Commerce Committee, Rep. Henry Waxman, D-Calif. Waxman and Markey presented their 648-page bill last month.

From 1969 to 1980, Congress passed more than a dozen environmental bills tackling everything from air and water pollution and garbage, as well as protections for fisheries, marine mammals and endangered species. In 1990, the Clean Air Act was overhauled to address the problem of acid rain created by the sulfur dioxide released from coal-burning power plants.

"We had two decades of extraordinary legislation and almost two decades of nothing," said Richard Lazarus, a Georgetown University law professor and author of "The Making of Environmental Law." "If this one passes, it will certainly be an outburst."

There are many reasons why Congress' chances to succeed in passing global warming legislation are improved this year, but by no means assured.

After President George W. Bush did little about global warming in his two terms, there is "a lot pent up demand" for action on climate, said William Ruckelshaus, the first administrator of the Environmental Protection Agency.

Both the Democratic-controlled Congress and President Barack Obama agree that legislation is needed to limit emissions of greenhouse gases and radically alter the nation's energy sources. They want to pass a bill by the end of the year.

"For the first time ever, we have got the political actors all aligned," said Lazarus. "That is not enough to get a law passed, but that is a huge start. We haven't been close to that before."

Unlike the 1970s, when the first environmental laws passed nearly unanimously, Republicans are opposed. They question whether industry and taxpayers can afford to take on global warming during an economic recession.

Then there is the question whether the public will have the appetite to accept higher energy prices for a benefit that will not be seen for many years. Climate change ranks low on many voters' priority lists.

Every year since 2001 has been among the 10 warmest years on record. Sea ice in the Arctic and glaciers worldwide are melting.

But the problems are not as apparent as they were in the 1970s, or even the early 1990s, when Congress addressed acid rain and depletion of the ozone layer.

"If carbon dioxide were brown, we wouldn't have the same problem," said Gus Speth, who organized the Natural Resources Defense Council in 1970. "But it's a subtle issue. ... The problems are chronic not acute, and it is largely invisible to people unless they're reading the newspaper or checking the glaciers or going to the South Pole."

In 1969, oil and debris in the Cuyahoga River in Cleveland burst into flames, an incident that led to the passage of the Clean Water Act. That same year, a blowout at an offshore oil platform off Santa Barbara, Calif., spilled millions of gallons of oil onto beaches. And long before that, a smog episode in Donora, Pa., in 1948 killed 20, sparking a crusade against air pollution.

"There was so much evidence — sort of smell, touch and feel kind of evidence — that the environment was really in trouble," said Ruckelshaus. "We had real problems, real pollution problems that people could see on the way to work. And there were rivers catching on fire and terrible smog events."

With climate, "you are asking people to worry about their grandchildren or their children," he said. "That is why it will be so tough to get something like this through."