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Hikers plan and climate change laughs.

Mini Chimi was taking a nero with her tramily when she replied to my email. “I believe there is a lot of fear out there associated with the high snow year on the [Pacific Crest Trail],” she told me. “I want to be a positive voice out here.”
Mini didn’t need to worry about coming across as anything else; her writing on The Trek, a blogging platform for long-distance, end-to-end “thru-hikers,” is punctuated by joyous clumps of exclamation points.
“WE ARE DOING IT!!!!” celebrates one post. “COWBOY CAMPING IS SO FUN!!!!!” she raves further on, about sleeping without a tent. Even “snow around mile 35!!!” — a section of high desert just north of the Mexican border — warrants Mini Chimi’s excitement, although it is snow that most hikers of the Pacific Crest Trail, or PCT, are dreading the sight of this year.
In the little more than a decade since Cheryl Strayed published her bestselling memoir about hiking the PCT, Wild (adapted into a movie starring Reese Witherspoon in 2014), interest in thru-hiking the 2,650-mile Mexico-to-Canada trail in a single season has skyrocketed. But in the same span of time, the Pacific Crest Trail Association (PCTA) — the nonprofit stewards of the trail — has grown increasingly worried that thru-hiking as we know it is on the verge of going extinct. Wildfires now regularly close vast sections of the trail in the late summer, and water sources in the desert and high Sierras are drying up, making remote regions virtually impassable. Hiking the trail end-to-end in one year, a bucket-list item for many long-distance backpackers, is now “almost impossible” due to climate change.
Though Mini Chimi is keeping her chin up, 2023 thru-hikers — who’ve quit jobs, bought one-way international flights, and sunk thousands of dollars into new gear — are already watching their odds of completing the trail this year evaporate, some before they’ve even begun (northbound hikers continue to start their trips through the end of May). But ironically, it isn’t extreme heat or wildfires that are scuttling plans. It’s the snow.
“This time of year, there is always snow on the trail,” Scott Wilkinson, the content development director of the PCTA, explained to me. “But this year, obviously, we’re talking about an order of magnitude much, much bigger.”
Due to the parade of atmospheric rivers that slammed the West Coast this winter, California remains buried under once-in-a-generation levels of snow. Ski areas are promising to stay open until “AT LEAST July,” and the Sierra Nevada might not melt out until well into August. This has caused a number of problems that aren’t typical of the trail, which has otherwise trended hotter and drier: A recent post in the Class of 2023 PCT Facebook group, which is administered by the PCTA, suggested that the precipitation this winter has resulted in a lush desert underbrush that is making it harder to spot rattlesnakes, increasing the likelihood of bites. The trail will likely get insufferably buggy this summer, and the West Coast superbloom is also expected to dry into fodder for wildfires.
But fires, one of the most foreboding late-season obstacles on the trail, still seem a world away. In parts of the southern Sierra Nevada, which hikers usually aim to hit around mid-June, the snowpack is still 300% above normal levels. “Right now, about 660 miles of the PCT in the Sierra Nevada are under snow,” Wilkinson told me last week. “That, at a normal trail hiking pace of 20 to 30 miles a day — I mean, that’s a month’s worth of hiking. In snow, it’s likely to be considerably slower than that.” He noted that while there are “a few people that are leading the pack” who have experience in snow conditions, for the most part, that level of snow is “pretty much a nonstarter.”
Firefly is one such hiker who is hoping to push through the Sierras (thru-hikers traditionally refer to each other by their trail names, which I’m honoring here). A retired San Diego Fire Department fire captain, Firefly left the trail in March at mile 151, just south of the San Jacintos, the first major mountain range that hikers encounter headed north. With a high point of over 9,000 feet (or 10,804 feet, if one detours off trail to bag Mt. San Jacinto), the San Jacintos will mark the highest elevation many of the less experienced thru-hikers will have ever stood at, and the steep, bare slopes are “nerve-racking under normal conditions, and downright treacherous if it’s icy,” as they are now, the Fatmap PCT guide cautions.
Part of the reason Firefly left trail was to take a snow travel class offered by the Sierra Mountain Center, which she'd signed up for in October 2022, before even knowing how bad this season was going to be. In the class, she learned how to use crampons, traverse steep snow slopes, and, critically, how to self-arrest using an ice ax. “It feels that a lot of hikers have already decided to skip the Sierra without even setting up to try it,” she wrote to me. “And that’s totally fine for them because it really looks overwhelming. It just feels like an opportunity for me to do something amazing, scary, challenging, and hard.”
Refill, a thru-hiker from northern Germany, managed to make it through the San Jacintos “as probably the third or fourth group,” by his estimate. He’s reflected in a Trek journal entry that “since the start of my planning, San Jac was the mountain range that scared me the most” — a sentiment that is common among PCT hikers, especially after a thru-hiker slipped on a patch of ice on Apache Peak and slid to his death in 2020. In the Class of 2023 PCT group, hikers have been busy exchanging beta about the conditions; one offered up a handy flowchart titled “So You’re Considering the Apache-Onward Section??” with the most common outcome being: Skip it! The local search-and-rescue group is getting to the point even quicker, urging hikers to entirely bypass the 60-odd miles through the San Jacintos, while the PCTA has posted sternly-worded reminders on Facebook that spots on the trail “will require mountaineering skills” and pose avalanche dangers: “Do not assume it will be okay or easy.”
Refill, for his part, is planning to take the skills he practiced with his tramily — that is, his “trail family” — in the San Jacintos and use them in the Sierra Nevada. “All in all, this sketchy and steep mountain range was very good training; we will probably start hiking at 3 a.m. every night in the Sierras,” he told me, describing a mountaineering technique that ensures traversing hard, firm, and more navigable snow during colder hours. “I WAS nervous about San Jacinto, as this range is known to be deadly and steep,” he went on. “I AM nervous about the river crossings in the Sierras.”
The water crossings are also what is keeping Firefly up at night. Outdoor educator Andrew Skurka lists over 30 PCT “High Sierra creek hazards” that still lay ahead of hikers on his website, some with ominous notes like “PCT hiker died here in 2017.” Already, a “critical backcountry bridge” in a section of trail about a month ahead of the lead thru-hikers “has been badly damaged [by snow] and will almost certainly mean long-distance hikers will have to reroute their trips around one of the most picturesque stretches of the High Sierra this summer,” the San Francisco Chronicle reports. The news isn’t encouraging from the PCTA, either: “Without a bridge, crossing the river is not possible anywhere in the general vicinity during high water,” a blog post from the organization warns. “The record-breaking snowpack this year essentially guarantees that high water conditions will exist into August, if not longer.” (White water rafters, meanwhile, are thrilled).
Serendipity is an experienced thru-hiker who completed the Appalachian Trail in 2022; her plans look more like the typical 2023 thru-hiker’s. “My tramily and I are planning to skip the Sierra and possibly come back later in the year, depending on conditions,” she wrote to me from a water cache on the trail just short of the 100-mile mark last week. “We are taking a cautious approach.” It’s not that she doesn’t want to thru-hike — “if the conditions were passable, we would have” — but “I am keeping a take-it-as-it-comes attitude, and [planning] accordingly as we get information,” she went on. “I don’t feel any pressure to attempt to take on unsafe conditions.”
Firefly was staying realistic too: “If there is significant warming or rain before the end of May or while I am in the Sierra, and the river crossings are gnarly or too difficult, then I will bail out, skip up to Northern California, and return in August to finish the Sierra,” she said, describing, like Serendipity, a strategy known as “flip-flopping” — skipping temporarily impassible or challenging trail conditions and returning to complete the sections when they’ve cleared up. Mini Chimi said she has already reworked her plans in this way: “We are ... having to skip around [in order to] avoid large amounts of dangerous snow,” she wrote to me during her “nero,” a “near-zero” mileage rest day. “We will be going back when the conditions are better to complete these sections.”
One day, even elaborate flip-flopping likely won’t allow hikers to complete all the PCT sections in a single season — such as if the Sierra has a snowless year, as is anticipated — but Wilkinson said the hikers I spoke to all have the right mindset. “A lot of hikers are rolling with it; they’re getting creative,” he told me. “They’re beginning to let go of this continuous journey concept in their minds.”
Among those who are on trail, though, letting go can still be easier said than done. “Last year on my [Appalachian Trail] thru-hike, I felt a certain ‘do it now!’ urgency, in part due to my age,” Serendipity said. “I feel a similar ‘do it now’ urgency on the PCT because of my age and also how the uncertainty of extreme weather conditions will affect the PCT.” Those not on trail feel this anxiety too: Thru-hiking the PCT has long been a dream of mine, one that I may now never realistically be able to complete — at least, not in the way I’d envisioned it. Losing that possibility is sad: I’ve alternated between denial (maybe I could still get lucky and pull it off?) and anger that this is our reality.
But like Mini Chimi, Wilkinson remains almost impossibly upbeat about the future of the PCT. “None of this spells the end of the trail,” he said. “This isn’t necessarily gloom-and-doom. It’s change, right? And change is never easy, especially when it’s as difficult to predict as what we’re experiencing now.”
The PCT is nothing if not a patient teacher of change: on the journey, spring turns to summer turns to fall; the trail weaves through six of the country’s seven eco-zones; and sometimes, years-in-the-making plans have to be reworked due to hydroclimatic events, a washed out bridge, or a dry lightning storm. The only way anyone ever gets from one border to the other is by surrendering to whatever the unknowable mile ahead may bring. Mini Chimi is right; you might as well be positive about each step, in that case. None of them can be taken for granted; every one of them, each year, becomes a more precious gift.
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The spinoff of Lawrence Livermore National Lab has a new 10-point plan to get onto the grid by the 2030s.
One of fusion energy’s newest startups, Inertia Enterprises, is betting that the fastest route to commercial fusion runs through one of the field’s oldest ideas. The company, which raised a $450 million Series A earlier this year, plans to build a power plant based on the laser-driven fusion system pioneered at Lawrence Livermore National Laboratory’s — the only tech yet to have produced more energy from a fusion reaction than it took to initiate it. Now, Inertia has shared its commercialization roadmap exclusively with Heatmap, detailing the 10 near-term capabilities it must demonstrate before this landmark experiment can become a grid-scale power plant by the mid-2030s.
The roadmap offers a route from the national lab’s impressive but commercially impractical fusion demonstrations to an economical power plant capable of producing electricity for the grid. At its core are a set of milestones — mostly aimed at developing cheap, mass-manufacturable components — that Inertia says it must clear before those individual systems can be integrated into a working plant. This road is not necessarily linear, however, as various teams will likely be working on many of these goals simultaneously.
At least the physics of Inertia’s approach are already proven, the startup’s CEO Jeff Lawson told me, pointing to the fusion experiments at Lawrence Livermore’s National Ignition Facility as a proof-of-concept. The lab’s demonstration of net energy gain caps more than six decades and $30 billion (in 2026 dollars) of U.S. fusion research. The remaining challenges, he argued, are all engineering-related, requiring “elbow grease, hard work, and smart people” rather than breakthroughs in fusion science.
"It seems to us like a startup or a commercial company of any variety should be focused on commercializing a proven scientific result, as opposed to actually trying to demonstrate the basic science to begin with," Lawson told me. Basic science, he argues, is better left to national labs and universities, where researchers can pursue "unbounded problems" that don’t align with the expectations and timelines of venture-backed startups.
Indeed, no fusion startup has yet achieved scientific breakeven, the milestone Lawrence Livermore first hit in 2022, and has since repeated numerous times. But leading players such as Commonwealth Fusion Systems and Helion Energy maintain that it’s only a matter of time before they validate the physics behind their own reactor designs, which they claim will be highly cost-competitive.
Lawson, on the other hand, readily acknowledged that Lawrence Livermore’s tech is uneconomical in its current form. His bet is simply that the more predictable path to a commercial reactor is to drive down the cost of the lab’s validated fusion approach, known as inertial confinement. This system relies on high-powered lasers firing at a millimeter-scale pellet of fusion fuel, compressing it to extreme temperatures and pressures until the atoms fuse. Today, the National Ignition Facility makes each individual fusion target by hand, a workable solution given that it only uses about a dozen per year.
That production model, however, isn’t remotely plausible for a grid-scale power plant. Because each fusion reaction lasts just a fraction of a billionth of a second, a commercial facility must fire its lasers at a fresh target about 10 times per second to generate continuous electricity — requiring the production of hundreds of millions of targets each year.
Scaling production to roughly a million pellets per day and making them inexpensive enough for commercial operation without compromising the strength or precision required for fusion ignition is central to Inertia’s roadmap. That includes goals five, seven, eight and nine — industrializing the manufacturing of the carbon shells that hold the fusion fuel, making the thin films that hold those carbon shells both durable and cheap, scaling up and automating fusion target assembly, and speeding up how fast targets are filled with the requisite deuterium-tritium fuel.
The other central focus of the roadmap is the laser system, which will ultimately consist of 1,000 individual units operating in concert to compress and heat the fusion fuel. Key priorities include reducing the system’s cost (goal two), dramatically increasing its firing cadence (goal three), and bolstering its durability to withstand high-intensity operations (goal four). Goal six also complements these efforts, calling for the development of a control system capable of tracking moving fusion targets to precisely align each laser shot.
Goals one and 10 bookend the journey with some broader milestones. The first focuses on increasing the fusion target’s energy gain — the ratio of fusion energy produced to laser energy delivered — to more than 25 times ignition. Today, the National Ignition Facility’s best-performing laser shot has yielded a gain of just over four times what it took to start the reaction. Goal 10 then zooms out to the ultimate objective: integrating all these technologies into a commercially viable power plant that can deliver either electricity or industrial heat to end customers.
To reach that point, Inertia has embarked on an industrial engineering hiring spree, recruiting folks with experience taking complex hardware systems from prototype to mass production, “not unlike the processes that are used in the semiconductor or consumer electronics world,” Lawson explained. The company has been making progress on its component development goals since the beginning of the year, he told me, and expects to announce the successful demonstration of a few of these milestones in the coming months. Lawson ultimately expects Inertia to complete the core components of its laser and target manufacturing systems by the middle of next year.
The team will spend the next two to three years integrating these individual pieces into two fully operational subsystems, a prototype laser system and a target manufacturing line. Around 2030, the company will begin combining those subsystems into a first-of-a-kind fusion power plant, which will also serve as the proving ground for the target chamber, tritium fuel breeding system, and power conversion system that turns fusion heat into electricity. By the middle of the next decade, Inertia aims to be generating power from this first plant, setting the stage for the company to build and connect additional grid-scale commercial power plants.
There are plenty of engineering trade-offs that the company will have to solve for. Take the decision around how to size the target chamber, for example. “If you make it bigger, your walls have an easier time and survive longer, but it’s more expensive. If you make it smaller, your walls have a tougher time because they’re closer to all the heat and energy that the fusion reaction is creating, but now your power plant costs less to build.”
But to Lawson, this represents exactly the type of problem Inertia was built to solve: complex engineering issues that come to the fore once scientists have demonstrated the fundamental physics are sound. He thinks other fusion companies may someday reach this stage, as well — though he’s unwilling to hazard a guess on exactly what approach or startup is best positioned to do so.
“There have been generations of scientists who’ve made their predictions about fusion energy and gotten it wrong,” he told me. “I’m not going to pretend to be smarter than them. All I’m here to say is, just knowing that one did work, we can commercialize it.”