(CNN) Beto O'Rourke on Monday released his plan to tackle climate change in his first major policy proposal as a 2020 candidate.

O'Rourke plans to invest $5 trillion over 10 years in infrastructure and innovation and also sets a goal to achieve net-zero emissions by 2050, according to an outline of O'Rourke's proposal which his campaign put out ahead of a tour of Yosemite National Park on Monday.

The former Texas Democratic congressman's plan called climate change "the greatest threat we face" and outlined a four-part framework to address this "existential threat" and "growing emergency."

If elected president in 2020, O'Rourke's "very first bill he sends to Congress ... will mobilize $5 trillion over 10 years — spurred by the single largest investment to fight climate change in history — to transform our aging infrastructure, accelerate innovation, and empower our people and communities to lead the climate fight," according to his plan.

O'Rourke's ambitious, first major policy rollout comes amid questions from voters and critics about how he would take on key issues should he be elected president.

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