The state of Montana has a constitutional obligation to protect its residents from climate change.

That was the stunning ruling from a judge who delivered a landmark decision on Monday. It compels Montana, a major coal and gas producing state, to consider climate change when deciding whether to approve or renew fossil fuel projects.

The state Constitution guarantees residents “the right to a clean and healthful environment.” In a lawsuit, Held v. Montana, 16 young people argued that the government had violated that right by enabling rampant development of fossil fuels, contributing to climate change and polluting the state.

The case went to trial in June, with the plaintiffs and their expert witnesses making a meticulous case that the state’s liberal permitting of oil, gas and coal projects, and its lax environmental oversight, were harming its residents.

The young plaintiffs testified about extreme weather events that threaten their families and their health. They also spoke of the anguish they felt as they considered a future dimmed by environmental collapse.

The state, which many had expected to attack the validity of climate science, instead argued that the issue should be decided by the Legislature. It was given a week to mount its defense, but rested after one day.

On Monday, Judge Kathy Seeley of Montana District Court unequivocally backed the plaintiffs. She found that the state’s emissions “have been proven to be a substantial factor” in affecting the climate and that Montana is responsible for as much carbon dioxide as is produced by Argentina, the Netherlands or Pakistan.

Montanans, she concluded, “have a fundamental constitutional right to a clean and healthful environment, which includes climate as part of the environmental life-support system.”

Establishing the facts

The Montana case could have broad implications in the fight to hold companies and governments responsible for climate change.

Around the world, there is a dramatic upswell of climate litigation, but few cases have made it to trial. As a result, there is little established case law about climate change, and even basic scientific truths, such as the fact that fossil fuel emissions are heating the planet, are not well established in the legal record.

Judge Seeley’s ruling is likely to provide an important building block for future litigation, including similar state cases in Hawaii, Utah and Virginia, as well as a federal case pending in Oregon.

“This was climate science on trial, and what the court has found as a matter of fact is that the science is right,” said Michael Burger, executive director of the Sabin Center for Climate Change Litigation at Columbia University.

“Emissions contribute to climate change, climate harms are real, people can experience climate harms individually, and every ton of greenhouse gas emissions matters,” Burger added. “These are important factual findings, and other courts in the U.S. and around the world will look to this decision.”

What’s next

The state said it would appeal the ruling to the Montana Supreme Court. It may also seek a stay on Judge Seeley’s directive that it begin considering climate change when approving new energy projects.

But for the broader legal fight over climate change, the judge’s decision will have an immediate impact.

“The legal community has been fearful that judges won’t understand these cases, and she blew that out of the water,” said Julia Olson, the founder of Our Children’s Trust, the nonprofit group that brought the case. “It was digestible, she understood it, and the findings were beautiful.”

Challenges to the clean energy transition

As we told you in yesterday’s newsletter, the renewable energy transition is moving with remarkable speed, but it’s still not going fast enough to head off the worst consequences of the warming planet. To speed things up even further will require persuading many holdouts .

My colleagues Jim Tankersley, Brad Plumer, Ana Swanson and Ivan Penn took a look at one big hurdle: If lawmakers want to ramp up renewables as quickly and cheaply as possible, they’ll need to bulldoze or build over some places that people treasure. And those people are crying out against solar farms, wind turbines and new power lines, filing lawsuits and passing laws stop or slow projects.

Meanwhile, the Times reporters Jack Ewing, Clifford Krauss and Lisa Friedman talked to individual consumers making pivotal choices with big consequences: Whether to buy electric cars, solar panels, heat pumps and electric water heaters that will play a key role in the energy transition. The words “climate change” often don’t play a big role.

“I’ve had several friends of mine that were, you know, not necessarily trying to save the planet,” said one farmer in Kansas who recently installed solar panels to keep his cattle cool on sweltering days. “They just wanted to save money.”

The biodiversity loss behind Maui’s fires

The fire that incinerated Lahaina is already the deadliest in the U.S. in over a century, and the official death toll is likely to grow. Global warming played a huge role, as we talked about last week. But Hawaii also vividly demonstrates how the effects of climate change can be compounded by the loss of native ecosystems.

The devastated town of Lahaina used to be wetland, as the Heated newsletter reported. Humans replaced many of the state’s native plants with huge plantations for crops like sugar cane and pineapple, which later were left fallow by large corporate landowners.

That left room for invasive grasses that now occupy nearly a quarter of Hawaii’s landmass, my colleagues Simon Romero and Serge Kovaleski reported. Those grasses become fuel for last week’s devastating fires.

The blazes set back years of efforts to restore endangered plant species, and sent conservationists rushing to protect birds and other species at risk of extinction. Going forward, the fires could make the state’s biodiversity loss even worse, because native vegetation is not adapted to fire and is unlikely to grow back after burning, one expert told The Verge.

—Manuela Andreoni

The weather report

A late-season heat wave has hit the Pacific Northwest, with several consecutive days of 100-degree Fahrenheit heat in places like Portland, Ore., raising the risk of wildfires.

“The low humidity and heat will continue to maintain tinderbox conditions in the Cascades, where we already have a few big fires,” said Clinton Rockey, a forecaster with the National Weather Service. Many areas in Oregon haven’t had much rain since May, leading to dry brush and timber that is easy to burn once a fire starts.

Temperatures across much of the South, which felt like a steamy boiler room this past weekend, will dip to more seasonable high temperatures of the 80s and 90s by midweek.

However, temperatures will begin to ramp up again, first in the Central Plains and then in the South, late this week, reminding people in those regions that summer isn’t over yet and the dog days have just begun.

—Judson Jones