Defense arguments are set to open in a landmark climate case brought by Montana youth

Attorneys for the State of Montana said Friday they will not call one of their top expert witnesses in the only youth climate lawsuit to make it all the way to trial in the U.S.

Climatologist Judith Curry, who disagrees with the scientific consensus that human activity is primarily responsible for dangerous warming of the planet, has provided written testimony, but will not be present in court this week.

Sixteen young Montana plaintiffs are suing state leaders in Helena, saying they've ignored scientific evidence and continue to promote fossil fuels, worsening climate change. They say that violates their right to a "clean and healthful environment," which Montana's constitution guarantees.

The state has tried multiple times to avoid going to trial, including two requests for the state Supreme Court to override prior rulings.

"We've had to fight so hard against an administration, a whole state that doesn't want us to be able to carry out our constitutional rights and has been avidly trying to deny us that opportunity throughout this whole process," says 18 year-old plaintiff Lander Busse, who has been waiting for three years for his day in court.

Busse and his family rely on hunting and fishing to stock their freezers for the winter. For him, this case is about saving what he loves about Montana.

When Lander and the other plaintiffs finally entered a Lewis and Clark County courtroom this past week, supporters lined the sidewalk outside to show support, clapping, cheering and waving signs.

Twelve of the plaintiffs took the stand, sharing their experiences living in Montana's changing climate.

"It's smokey, the world is burning," testified 20 year-old Claire Vlases, recounting summer wildfire smoke often blocks views of the mountains surrounding the Gallatin valley where she lives.

Thick smoke and burnt orange skies like the East Coast recently experienced have been a regular occurrence in Montana for years now.

Vlases says it sometimes feels like her lungs are full of fire.

"That sounds like a dystopian horror film, but it's not a movie. It's real life. That's what us kids have to deal with," she said.

Vlases and her co-plaintiffs are asking the state to set a limit on greenhouse gas emissions. Montana is America's fifth largest coal producer. The plaintiffs say both the legislature and executive branch continue to prioritize fossil fuels.

They called 10 expert witnesses, including University of Montana Researcher Steven Running. He contributed to a U-N Intergovernmental Panel on Climate Change report which won a Nobel prize in 2007.

"Climate change is real," Running testified. "The earth is warming up and that the driver for this is burning fossil fuels."

Attorneys representing the state were generally deferential to the young plaintiffs. Their questions for the expert witnesses largely sought to cast doubt on Montana's ability to affect climate change.

"Montana's emissions are simply too miniscule to make any difference and climate change is a global issue that effectively relegates Montana's role to that of a spectator," argued Montana Assistant Attorney General Michael Russell.

Attorneys for the state get the chance to present their defense. On Friday they announced they would not call one of their expert witnesses, a climatologist who disagrees with the scientific consensus on climate change.