WASHINGTON (CNN) -- Democrats, now that they hold the majority in Congress, are pushing one of their signature issues to the front burner: Global warming. Rep. Henry Waxman of California announced legislation Tuesday to gradually cut greenhouse-gas emissions back to the level of 1990.

Addressing a crowd of about 3,000 environmental activists gathered under a sunny, spring like day at the west front of the U.S. Capitol, Waxman said, "Today, I am going to be introducing the Safe Climate Act, with more co-sponsors in the house than any other piece of legislation dealing with this subject."

The bill is co-sponsored by more than 125 members, he said.

The Safe Climate Act would freeze U.S. greenhouse gas emissions in 2010, at the 2009 levels. Beginning in 2011, it would cut emissions by roughly 2 percent each year, reaching 1990 emissions levels by 2020.

The legislation would impose a cap and allow credits to be traded among industries making progress toward cutting greenhouse gas emissions. The bill would also encourage the development of renewable energy, and encourage Americans toward greater energy efficiency and cleaner cars.

A spokeswoman for Waxman told CNN the bill will be entered by Tuesday night.

-- CNN's Paul Courson