The plans come out on the same day CNN will host its climate crisis town hall meeting, featuring one-on-one interviews with 10 Democratic presidential candidates, including Buttigieg and Harris. The seven-hour event will be streamed live on CNN.com, on the CNN app and SiriusXM Channels.
Harris' $10 trillion plan, called a Climate Plan for the People, encourages electric vehicles, solar panels, wind turbines and other forms of clean energy. The Democratic senator from California's goal is to create a carbon-neutral economy by 2045.
The United States is the biggest greenhouse gas emitter on the planet and has an obligation to fight against climate change, Harris said.
"From families devastated by hurricanes in the South and the East, to farmers facing flooding in the Midwest, to firefighters battling wildfires in the West, one thing is clear: we need to take bold, direct action," Harris said. "Yes, it won't be easy. It will be a fight against powerful interests. But I know we can get this done because this is a fight I have taken on before and won."
Her plan holds polluters accountable, transforms the economy from one based on dirty fossil fuels to clean renewable energy, protects natural resources and leads the world in climate change action.
"Successfully combating the climate crisis will require that all Americans benefit from the economic and environmental transformation that comes from replacing dirty fossil fuels with clean renewable energy," Harris said in a statement.
Buttigieg's plan is much less expensive, $1.1 trillion, and sets a goal of net-zero emissions by 2050. The mayor of South Bend, Ind., wants to create 3 million clean energy and infrastructure jobs in the next decade.
That includes a $200 billion investment over 10 years in clean energy research and development and a $250 billion Clean Energy Bank to finance innovative technologies. It also includes private investment from U.S. companies to develop green technologies that would be matched by another $250 billion from the government. It also includes a $50 billion seed fund for riskier and experimental ideas.
The cost of not doing anything will be high, too, Buttigieg said. And mankind has to change course in the next decade or global warming will "reach catastrophic levels."
"As temperatures and sea levels rise, so do the costs of food and flood insurance," Buttigieg said in a statement. "New health issues from heat, air pollution and the spread of infectious diseases are growing. From hurricanes devastating Puerto Rico to fires ravaging the Amazon, climate change is affecting everyone, everywhere."
Democratic presidential candidates Cory Booker, a senator from New Jersey, and Julian Castro, the former Housing and Urban Development secretary, each proposed their own climate action plans Tuesday. Booker's plan costs $3 trillion while Castro's costs $10 trillion.