A Senate committee on Tuesday launches three long days of hearings on a Democratic climate bill in a bid to further convince an international summit in December that Washington is serious about tackling global warming.

The Senate's Environment and Public Works Committee will kick off Tuesday's hearing at 9:30 a.m. EDT with a panel of heavy-hitters from President Barack Obama's Cabinet: the secretaries of energy, transportation and interior and the head of the Environmental Protection Agency. Joining them will be the chairman of the Federal Energy Regulatory Commission.

According to an EPA statement, the officials will focus on creating a system of clean energy incentives while confronting the threat of carbon pollution.

The government estimates that the electric power sector contributes 39 percent of energy-related greenhouse gas emissions in the United States, while 34 percent comes from the transportation sector and 27 percent from the use of fossil fuels in homes, commercial buildings and industry.

Obama and Democrats in Congress are pursuing legislation that would create a cap and trade system requiring utilities and industries to reduce their emissions of carbon dioxide and other gases associated with global warming over the next 40 years. Companies would have to obtain dwindling numbers of pollution permits from the government and hundreds of dollars worth of permits could be traded on a new financial market exchange.

Committee Chairman Barbara Boxer hopes to finish reviewing the legislation and vote on it in coming weeks.

If so, that could be the last major action by the Senate on climate change legislation this year, before countries from around the world meet in Copenhagen in December to try to chart new, tougher goals for reducing carbon emissions to head off worsening droughts, floods and melting polar ice.

U.S. leadership is considered essential to the global talks, since the United States is the leading carbon polluter among developing countries.

At the United Nations on Monday, a senior official lowered expectations of a deal in Copenhagen. Janos Pasztor, Secretary-General Ban Ki-moon's climate advisor, said the UN head was planning for post-Copenhagen talks.

Most Senate Republicans oppose the cap and trade bill, saying it would force U.S. companies to move more manufacturing abroad while also raising consumers' energy prices.

High-ranking Senator Lamar Alexander, one of the few Republicans to declare that climate change is real, said that during this week's hearings, he and his fellow Republicans on the committee will offer an alternative to cap and trade.

Before we embark upon a scheme that would send jobs overseas and charge Americans hundreds of billions of dollars a year in new taxes ... we might look for another solution, Alexander told reporters.

That solution, he said, is a four-pronged plan to encourage a huge expansion of the nation's nuclear power, expand offshore drilling for natural gas, beef up research on alternative energies and convert half of the nation's car and truck fleet to electric power.

Daniel Weiss, of the liberal Center for American Progress, called Alexander's proposal a recipe for a much larger federal (budget) deficit with government spending to fund alternative energy research and the potential for huge taxpayer exposure from government-backed loan guarantees for nuclear plants.

Weiss also noted that scientists argue that a 20 percent reduction in U.S. carbon emissions is needed by 2020 and it likely would take longer than that to get new nuclear power facilities on line.

While Republicans argue that the Democrats' climate change bill would result in substantially higher consumer prices, an early EPA analysis found that, like a House-passed climate bill, there would be small increases, in the range of $80 to $111 per year.

Nevertheless, Republicans said they will await more detailed analysis and hinted they could delay the environment panel's work on the bill until they get that information.

On Wednesday and Thursday, the committee will continue its hearings, with testimony from industry officials, environmental interests, national security experts, labor unions and others.

(Editing by Eric Walsh)

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