Sen. Bernie Sanders, I-Vt., upended the climate change debate in the Democratic 2020 primary last week when he proposed a staggering $16.3 trillion federal investment over 15 years in renewable energy and public infrastructure.
It is by far the largest proposal by any of the candidates in the field. Former Vice President Joe Biden and Sen. Elizabeth Warren, D-Mass., Sanders' fellow top-tier candidates, have proposed much smaller plans that nonetheless have costs in the trillions. Sen. Kirsten Gillibrand, D-N.Y., who dropped out of the race late Wednesday afternoon, had been the next closest candidate, with her proposal for a $10 trillion "moonshot" plan for the next decade.
The steep price tag for Sanders' plan created a wave of skepticism, but activists argue that ideas, not price, should be the main concern when it comes to confronting climate change.
"I don't think looking at the price tag is the best reflection" of the candidates' platform diversity, says Ryan Schleeter, senior communications specialist with Greenpeace USA. "What is setting them apart is their willingness to name the problem."
Candidates have centered much of the climate debate around the Green New Deal proposed by Rep. Alexandria Ocasio-Cortez, D-N.Y., and Sen. Ed Markey, D-Mass. It calls for a fundamental reworking of American public infrastructure and energy consumption, with aspirational goals to reduce the country's carbon footprint to net-zero by 2030.
Every Democratic candidate has endorsed the framework of the Green New Deal but has different ideas on how to implement it, not unlike the debate centering around "Medicare for All."
"It's as healthy as it can be," Michael Brune, executive director of the Sierra Club, says of the Democratic climate debate. "We want to see a competition of ideas. We want to see policy teams that are well resourced to have differing perspectives."
Republicans and some Democrats argued that the ideas are too radical and expensive. Estimates from the American Action Forum, a center-right policy think tank, put the overall cost of the Green New Deal at between $50 trillion and $90 trillion over the next decade.
But activists such as Schleeter say feasibility is not the standard when it comes to climate. "The bar is set by: What does science say is necessary?" he said.
Sanders' plan aims to reach a 100% renewable transportation and electric grid by 2030, as well as "complete decarbonization" by 2050. It would also declare climate change a national emergency and pledges to create more than 20 million well-paying jobs.
Most significantly, Sanders' plan calls for a total end to federal investment and subsidies in the fossil fuel industry, which comprises the bulk of the American energy sector.
"Some candidates have been giving it more attention than others, but Sanders' plan sets the tone," says Garret Blad, national press coordinator with the Sunrise Movement, a grassroots climate change advocacy group. "He sets the bar higher for the other candidates."
Even so, candidates have embraced the aspirations of the Green New Deal and have made it a crucial part of their climate change platforms.
Biden's climate plan is more modestly priced than other frontrunners' but still proposes a substantial 10-year investment of $1.7 trillion, $400 billion of which will be dedicated to "clean energy research and innovation."
Biden's plan proposes a mix of state, local and private sector investments totaling $5 trillion, relying less on federal involvement to spur a shift in energy consumption. Biden's proposal also relies on controversial "carbon-capture" technology, as well as investments in nuclear energy, which put him in stark contrast to Sanders.
Sanders' plan eschews nuclear energy development entirely, instead proposing a gradual phasing out of nuclear energy reliance. Nuclear energy accounted for 9% of America's total energy consumption in 2017, according to the U.S. Energy Information Administration.
Warren, who along with Sanders is considered a member of the party's left wing, proposed a plan for a $2 trillion investment over 10 years.
Warren's plan includes the creation of a "National Institutes of Clean Energy" to manage a $400 billion "Green Apollo Program," designed to spur green energy research and development; a $1.5 trillion "Green Industrial Mobilization" of American-made renewable energy products; and a $100 billion "Green Marshall Plan" to encourage foreign investment in American renewable products.
Warren has also proposed a Climate Risk Disclosure plan that requires companies to disclose how climate change will affect their business in the future.
The recent slew of proposals comes in the wake of a decision by the Democratic National Committee to uphold its ban on single-issue debates, which was met with criticism by activists who felt the subject needed a dedicated spotlight in the primary debates.
The controversy has happened in the lead-up to a "Climate Crisis" town hall hosted by CNN in September. So far, 10 candidates have qualified for the town hall, which is planned to specifically address each candidate's climate change platform. Five of the candidates still have not released detailed climate change plans.
"Our hope is that candidates will learn from each other," Brune says. "No single campaign has a monopoly on good ideas."
Clarification: This story has been updated to reflect that Sen. Kirsten Gillibrand dropped out of the race late Wednesday afternoon.