Over the course of his two terms in office, Gov. Tim Walz of Minnesota has quietly emerged as one of the nation’s most forceful advocates for tackling climate change.

Governor Walz, who has been tapped by Vice President Kamala Harris as her running mate according to two people briefed on the matter, most recently made national headlines for labeling the Republican ticket “weird.”

But back in St. Paul, Mr. Walz has been increasingly focused on the threats posed by climate change to his state and has been enacting ambitious policies designed to slash the use of the fossil fuels that are dangerously heating the planet.

Most notably, in 2023, Mr. Walz signed a law requiring Minnesota to generate all of its electricity from wind, solar and other carbon-free sources by 2040, eliminating the climate-warming pollution generated by coal and gas-fired power plants. That law came in the midst of a legislative session in which Minnesota Democrats, working with Governor Walz, pushed through nearly 40 other climate initiatives. In June, he signed a law designed to speed the implementation of the 2040 clean power mandate, by streamlining the permitting of renewable electricity projects.

“As I sign this legislation, communities from one end of our state to the other are looking at months of rebuilding after an extreme weather event exacerbated by climate change,” Governor Walz said in June, after catastrophic flooding devastated parts of the state.