WASHINGTON — Senator Kamala Harris of California released an ambitious new climate change plan early Wednesday, calling for $10 trillion in spending over a decade to combat human-driven global warming and a new tax or fee on companies that emit greenhouse pollution.
Ms. Harris unveiled her plan hours before a CNN town-hall-style event on global warming, which 10 Democratic candidates are scheduled to attend — the first time in a presidential campaign that the question of what to do about the heating planet has merited its own major forum on prime-time television.
Ms. Harris’s announcement also came one day after three other candidates released climate plans, including Senator Elizabeth Warren of Massachusetts, a leading rival for the nomination.
Ms. Harris, a former California attorney general, styled herself as a uniquely qualified prosecutor-in-chief who would maximize the power of the legal system to penalize corporate polluters and deliver “climate justice” to poor communities that suffer disproportionately from the impacts of climate change, like flooding, heat waves and food and water shortages.
“Climate is obviously an important issue to Democratic primary voters, and the candidates are responding,” said Robert Shrum, a veteran Democratic consultant and director of the Jesse M. Unruh Institute of Politics at the University of Southern California.
Many of the candidates’ plans, including Ms. Harris’s, bear similarities to proposals championed by Gov. Jay Inslee of Washington, who focused his presidential campaign on combating climate change but dropped out last month after it became clear he was unlikely to qualify for the next primary debate.
Mr. Inslee would not have been invited to the climate change forum, either, after failing to reach 2 percent support in four qualifying polls. But analysts said that Mr. Inslee’s influence on the rest of the Democratic presidential field was clear.
“Jay Inslee wrote a super-set of climate policy options, and candidates are taking subsets of Inslee ideas,” said Kevin Book, an analyst with ClearView Energy Partners, a nonpartisan Washington research organization.
Mr. Inslee released six detailed climate plans, totaling over 200 pages. He said he hoped they would help “raise the ambition” of other candidates’ climate policies, and he has since had conversations with several candidates about how to incorporate his ideas into their plans, said his former campaign spokesman, Jared Leopold.
On Tuesday night, Ms. Warren released a broad new climate change plan — her third such plan of the campaign — in which she explicitly adopted some of Mr. Inslee’s policies. “While his presidential campaign may be over, his ideas should remain at the center of the agenda,” Ms. Warren wrote.
Three other Democratic presidential candidates — Senator Cory Booker of New Jersey, Senator Amy Klobuchar of Minnesota and Julián Castro, the former housing secretary — have also released climate change plans since Sunday.
Ms. Harris’s plan includes many of the same basic policy elements as those of her rivals: a blueprint to end fossil fuel pollution from electricity generation by 2030, a halt on new fossil fuel leases on public lands and the imposition of aggressive new regulations on vehicle tailpipe pollution.
Environmental policy experts noted that Ms. Harris’s record on advancing climate change policy was thin, though she was an early advocate of the Green New Deal. But they said her focus on using the courts as a muscular tool to push through concrete greenhouse gas reductions could be effective, given that Congress has failed to do so.
“She’s going to throw the book at climate,” Mr. Book said. “It could be one way to meet the challenge of making radical new change with decades-old laws.”
In her new proposal, Ms. Warren adopts Mr. Inslee’s plan to eliminate planet-warming emissions from power plants, vehicles and buildings over 10 years, and adds an additional $1 trillion in spending to subsidize that transition. The spending would be paid for, she said, by reversing the Trump administration’s tax cuts for wealthy individuals and corporations.
Like Mr. Inslee’s proposal, her plan would set regulations aimed at retiring coal-fired power plants within a decade, but also fund health care and pensions for coal miners. It would create new federal regulations on tailpipe emissions with the goal of achieving zero emissions from new light-duty passenger vehicles, medium-duty trucks and buses by 2030.
Mr. Castro’s plan also includes several ideas either directly adopted from or developed in consultation with Mr. Inslee, such as a plan to replace all coal-fired power generation with zero-emissions sources by 2030, and a proposal to marshal $10 trillion in federal, state, local and private spending on jobs associated with the transition from polluting to nonpolluting energy.
Also at least some echoes of Mr. Inslee’s proposals are included in Mr. Booker’s plan, which calls for $3 trillion in spending to achieve a carbon-neutral economy by 2045, and in Ms. Klobuchar’s plan, which calls for reinstating Obama-era regulations on fossil fuel emissions to put the nation on track to a carbon-neutral economy by 2050.
Senator Bernie Sanders of Vermont, a rival of Ms. Warren’s on the left, has not explicitly taken up Mr. Inslee’s ideas. Instead, analysts said, he is trying to win over the progressive wing of the Democratic Party with a climate plan that takes its name from the Green New Deal and has the biggest price tag of all the candidates’ proposals — $16.3 trillion over 15 years. He has called for banning fracking to extract natural gas, and for halting the import and export of coal, oil and natural gas.
“I think Sanders is looking for ways to prove that he’s the true progressive in the race,” said Paul Bledsoe, a lecturer at American University’s Center for Environmental Policy.
Mr. Bledsoe said Wednesday night’s forum could also be an opportunity for former Vice President Joseph R. Biden Jr. to burnish his image. Mr. Biden’s climate plan, which calls for $1.7 trillion in spending over 10 years, initially won praise from environmental activists. But he came under attack from other candidates at the second Democratic debate for not being ambitious enough.
Polls reflect that climate change is a rising concern among voters.
In a survey published by Quinnipiac University last week, a majority of registered voters nationwide, 56 percent, say that climate change is an emergency. That majority included 84 percent of Democrats, but 81 percent of Republicans say that climate change is not an emergency.
Voters also think that the United States is not doing enough to address climate change, with 67 percent of voters saying more needs to be done.
Republican officials say the plans that Democrats have devised to address climate change will decimate the economy.
Mandy Gunasekara, a former policy adviser at the Environmental Protection Agency under the Trump administration, branded Democrats’ plans as socialist takeovers of the economy.
“Most Americans who talk about climate change, when you ask them, ‘O.K., how much are you willing to pay,’ it’s minimal to none. These trillion-dollar plans that each of them are putting up need some measure of honesty,” she said.
Tim Murtaugh, a spokesman for President Trump’s re-election campaign, wrote in an email, “The Democrats’ radical approach to energy is to eliminate the use of all fossil fuels, which would kill more than 10 million jobs and inflict economic catastrophe across the country.”
Mr. Bledsoe said there was some political danger for Democrats in attempting to outdo one another.
“In all honesty, every one of the climate plans proposed is more ambitious than anything that’s ever been remotely contemplated before,” he said. “But the danger is that they ignore the nuts and bolts of energy politics of swing states and risk handing Trump the election.”