Lake Palcacocha in the Peruvian Andes. Felipe Fittipaldi for The New York Times

Brooke Jarvis, whose mastery of the complex environmental story we have pointed to a couple times already, shares the story below about a novel legal approach to fighting climate change. It is long, detailed and even more complex than the other stories we have seen by her. But if her subject prevails, the result may be even more profound as well. These two photos alone should draw you in. Thanks to the New York Times Magazine:

The city of Huaraz in the Peruvian Andes. Felipe Fittipaldi for The New York Times

In the mountains far above the red-brick city, behind a locked gate, there is a great, green valley. Its high stone walls are streaked by waterfalls; its floor dotted with flowers and grazed by horses and cows. Six boulder-strewn miles beyond the gate, the valley ends abruptly at an enormous wall of rock and ice. Beneath it lies a stretch of calm, bright water in milky turquoise — Lake Palcacocha. Though few of its residents have ever seen this lake, the city below lives in fear of it.

On Dec. 13, 1941, a piece broke off a hanging glacier and fell into Palcacocha, creating a great wave that overwhelmed a natural dam and sent a flood surging toward Huaraz, a provincial capital in the Peruvian Andes, about 14 miles below. A third of the city was destroyed and at least 1,800 people were killed. In response, the government reinforced the natural dam and installed drainage tubes to lower the level of the lake. Huaraz boomed to 130,000 inhabitants from 20,000. Occasionally there was a scare — a rock slide into the lake in 2003 sloshed a smaller amount of water over the edge, causing panic — but to many people in Huaraz the danger began to seem remote. Until it became clear that the lake was getting bigger.

In 2009, glaciologists found that amid the widespread melting of Andean ice, the amount of water held in Palcacocha had increased by 3,400 percent over just a couple of decades. Even more worrying, this melt associated with climate change was destabilizing the glaciers hanging above it, making major avalanches more likely. The regional government declared a state of emergency and began posting guardians to watch the lake around the clock.

The guardians of the lake live above Palcacocha, in a little stone house with a tin roof. It was built by hand from nearby rocks and has no insulation, though at 15,000 feet the air is thin and the cold brutal, even in summer. There is no heat apart from a cook fire, and few supplies: raincoats, warm blankets, flashlights for working at night, snowshoes for working in winter.

On a cold summer day in February, I looked up from the lake to see a man descending a zigzagging trail. He walked lightly across loose boulders to the water’s edge, where a large ruler pierced the surface. He read it, and then turned to climb the switchbacks back to the hut, where a radio was wired to what looked like a car battery. It was his job, shared with two other men, to report on the status of the water levels every two hours, day and night…

Read the whole story here.