Four senior members of President Barack Obama’s cabinet will testify on the need for strong action by Congress to tackle global warming, saying such a move would assert US leadership on the issue before the Copenhagen global climate conference in December.

They include Energy Secretary Steven Chu, Interior Secretary Ken Salazar, Transportation Secretary Ray LaHood and Environmental Protection Agency administrator Lisa Jackson.

Also scheduled to appear before the Environment and Public Works committee will be Jon Wellinghoff, chairman of the Federal Energy Regulatory Commission, the agency that regulates interstate transmission of electricity, natural gas and oil.

Senator Barbara Boxer, a California Democrat, who chairs the committee, and Senator John Kerry, a Massachusetts Democrat, introduced climate legislation that aims for a 20% cut in greenhouse gases by 2020.

Their “Clean Energy Jobs and American Power Act” would require a 42% reduction by 2030 from 2005 levels and 83% for 2050, similar to a bill narrowly passed by the House in June. The House would require a 17% reduction by 2020.

The early Senate bill is similar to the House version in that it would create a cap-and-trade system to achieve emission reduction targets. However, it would give away 75% of emission allowances to large polluters versus 85% in the House bill, instead of auctioning them as Obama wanted. Neither bill says how allowances would be distributed.

The oil industry and several others that heavily pollute criticized distribution of the permits, arguing they were shortchanged in the proposed allocation process. The permits could be traded on a new financial market exchange under the Boxer-Kerry bill.

Republican leaders in Congress staunchly oppose both versions of the cap-and-trade bill as a “jobs-killing national energy tax,” and unfair to the oil and nuclear sectors. They also argue the bill will sharply raise the cost of doing business in the US, sending jobs overseas.

Some Republicans have indicated they could support some type of climate change legislation if it were more balanced in support of all energy sources including oil, natural gas and nuclear.

Senator Lamar Alexander of Tennessee says that he and six other Republicans on the committee will introduce an alternative to cap-and-trade.

He says the key to greater US clean energy independence is to build dozens more nuclear power plants, expand offshore natural gas exploration and production, accelerate research on alternative energies and vigorously pursue conversion of 240 million US cars and trucks to electric power.