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The eastern and northern United States are suffering under a hazy, poisonous cloud of wildfire smoke, produced by out-of-control forest fires in Quebec and Nova Scotia. The most toxic soot and ash are sitting virtually on top of North America’s most densely populated corridor, clouding the air in New York City; Toronto; Ottawa; Philadelphia, Washington, D.C.; and Norfolk, Virginia.
Air pollution alerts are in effect across the United States and Canada, affecting roughly 150 million people.
This is Heatmap’s set of commonly asked questions about the crisis. We’ll keep it updated throughout the event.
Hundreds of wildfires have raged across northern Quebec for the past few weeks, driven by unusually warm and dry conditions.
Then on Monday, a low-pressure system surrounded by counterclockwise winds moved just off New England’s coast. Its strong, dry gusts fanned the flames in Canada, then pushed the resulting smoke and ash into the eastern United States.
Intense Canadian fires are unusual this early in the season, but the fires this year were fed by a warm spring and drought-like condition, Kent Moore, an atmospheric-physics professor at the University of Toronto, told me. Because the fires took hold before the vegetation could “green up” for the spring, the conflagrations grew more rapidly than they normally would, he said.
The dry conditions also helped the fires ignite the soil itself. “Because the soil was so dry — because of the dry winter and the dry spring — the fire got into the ground,” he said. “The vegetation below ground started to burn, and those are much harder to put out.”
This is likely one of America’s worst days for air pollution in several decades, in terms of the number of people affected and the severity of the exposure, Marshall Burke, an economist and sustainability professor at Stanford, told me.
“It’s pretty off the chart,” Burke said. Wildfire smoke is affecting New York City much more acutely — and much earlier in the year — than it has at any time since 2006, when contemporary air-pollution data began to be kept.
It is difficult to attribute a single unprecedented event to climate change, and the climatology of wildfires in eastern North America is particularly challenging. (Climate change has more clearly worsened wildfires out West.) “This is probably an unlucky year for Canada, as far as wildfires go,” Moore, the atmospheric physicist, said.
But wildfires will become more likely across Canada as the climate changes, he said. And while climate change should broadly increase rainfall across Canada, it will also increase the likelihood of heat waves and more extreme spring and summer temperatures, which can make wildfires more likely.
“Nova Scotia has always had wildfires. It’s just they’ve had more wildfires this year than they have on average for the whole year,” he said. “There’s always going to be wildfires, but there’s going to be more of them.” As Canadian cities sprawl into previously uninhabited woodland areas, he added, the human impacts of wildfires will increase — even if the number and intensity of wildfires does not.
First, consult the air quality index at AirNow.gov. The AQI is a unit-less index of air quality running from zero to 500; any reading above 100 would rank as unusually polluted in the United States. On Wednesday afternoon, some air sensors in New York and New Jersey indicated that the AQI exceeded 400.
If it’s higher than 100, then the most vulnerable groups of people — including children, the elderly, anyone with a cardiopulmonary condition, and pregnant women — should limit strenuous activity outdoors. If higher than 150, then people should generally try to limit their outdoor activity; at levels above 200, the air is considered unhealthy and everyone should try to go outside as little as possible.
If you think you might be especially vulnerable, err on the side of caution. Recently, a body of new and large-scale studies have shown that air pollution is generally worse for the body and brain than previously thought.
Then, if you’re in an area with hazardous air pollution, consider how to limit your exposure to the air as much as possible. Keep your doors and windows closed. An air filter outfitted with a HEPA filter can improve the air in a home or apartment. It should generally be closer to the most sensitive people.
“Any pregnant moms — if my wife or anyone I knew was pregnant right now — I would be texting them to stay inside and sit by an air filter,” Burke told me. Exposure to severe air pollution during pregnancy has been shown to increase the risk of preterm birth, and it can reduce a child’s lifelong earnings, cognitive performance, and other indicators, he said.
A KN95 or N95 mask — the type of high-filtration mask used to prevent COVID infection — can also significantly limit your exposure to soot and ash. If you are in a sensitive group or are worried about air pollution’s health effects, you could consider wearing a mask inside if you have no other way to filter the air.
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At this point, I think it’s clear that AI data centers are unpopular.
You probably know it, at least. I was preparing talk about data center opposition on a podcast today and I took the opportunity to dive back into our data, so I certainly know it. At this point, we’ve written about results from our polling that show Americans overwhelmingly oppose local data center construction, that majorities of Americans now support a national data center moratorium, and that the only group of Americans who feels more optimistic than pessimistic about artificial intelligence is … men older than 65 years old.
So I got curious: Given all that, who actually supports AI data centers?
One question from our recent Heatmap Pro poll, conducted by Embold Research, helps give us a sense. This is the profile of someone our data says would support a data center built in their local area:
A few facets stand out. These data center YIMBYs are more likely to be men, and more likely to be 2024 Trump voters, but they’re not locked into one age demographic or voting cohort. A third are Harris supporters, and roughly a third are women. Data center YIMBYs are more likely to be older than 50, but the majority isn’t overwhelming.
Perhaps more surprising: The group has many more people who voted third-party in the 2024 election (8%) than the general population (just under 2%), although that response could also include people who didn’t vote. (Alas, the data can’t quite confirm how many in this group are libertarian.)
What’s perhaps most interesting: This group overwhelmingly believes that artificial intelligence will make their lives better. And in heartening news for climate advocates, they are even more likely to support a given data center project if it is powered by renewables.
I was going to joke that the profile is essentially a newly retired engineering dad — except that, to my surprise, these data center YIMBYs are far less gender imbalanced than the American engineering profession. (They’re also less gender-imbalanced than American Tesla owners.) So I’ll leave it at that.
Five takeaways from the latest Lazard Levelized Cost of Energy report.
It’s all getting more expensive.
That’s the conclusion of the investment bank Lazard’s latest report on the levelized cost of energy, one of the most closely watched and cited energy reports of the year.
Levelized cost of energy measures the dollars per megawatt-hour a power plant needs to earn in revenue to break even over the course of its lifetime in present-value terms.
What makes LCOE so alluring is that it’s a way to compare any type of generator, whether it requires a large upfront investment but has few operating costs, like a utility-scale solar project, or whether its expenses are largely fuel costs incurred in the future, like a combined cycle natural gas plant. This is also why LCOE has its critics, who point out that a solar panel that only runs during certain times of day has a different value to the electricity system than a natural gas plant that can ramp up and down quickly or a nuclear plant that provides steady baseload power.
Anyway, here’s what we can learn from this year’s Lazard report.
Curves that were once gently sloping downward are starting to look like incipient U’s. While longterm LCOE falls are still dramatic and impressive for some technologies — utility solar has fallen from $359 per megawatt-hour in 2009 to $69 in 2026 — the short term rises are worrisome. That $69 per megawatt hour represents a nearly 10% increase from 2025, when utility-scale solar had a LCOE of $58. And it’s not just renewables — the LCOE for a combined cycle natural gas plant rose from $78 per megawatt-hour to $90 in the past year. Gas plant LCOE got as low as $60 in 2021. That’s a 50% price hike in just five years.
Lazard attributed the increase in solar and wind LCOE to “higher capital costs, sustained interest rates, tariff pass-through and supply chain repricing.” These technologies are also the most “sensitive” to subsidies by way of the tax code, with federal tax tax credits taking the low end cost of utility solar to as low as $16 per megawatt hour. To the extent those tax credits are no longer available or weren’t accessible due to strict eligibility rules, that could be a source of future upward pressure on costs.
That being said, renewables “maintain their relative cost advantage despite facing the same cost pressures affecting the rest of the generation stack,” the Lazard analysts concluded.
Natural gas, meanwhile, is seeing prices spiral upward on huge and growing customer demand.
“Continuous upward revisions to demand projections have driven a sharp increase in announced new-build gas generation despite a 15-year high LCOE and historically long development lead times,” according to Lazard.
The report hints at what LCOE is not always able to capture, namely that generators like gas have attributes besides low cost that make them attractive. “New gas combined cycle plants offer the lowest-cost dispatchable power in high-demand and low-cost-gas environments,” the analysts point out.
Anyone building a new combined cycle gas plant, however, will have to deal with the high cost and low availability for turbines, which is “extending development timelines well beyond historical norms.” That provides an opening for renewables that can be deployed quickly and cheaply, like solar and accompanied by battery storage.
In 2019, the low end of LCOE for onshore end was $28 per megawatt-hour, according to Lazard’s figures, and the high end was $54. In 2026, however, the low end costs sits a bit higher at $37 per megawatt-hour, but the high end cost rose to $99. There’s a similar story for utility solar: in 2019, the spread between low and high was a snug $8 per megawatt-hour, while this year it’s ballooned to $58.
The broadening range is “likely reflecting that some project developers have been better able to mitigate broader cost pressures across supply chain and project-level economics than others,” the Lazard analysts wrote.
The Lazard report doesn’t just look at the discounted cost of individual generators over their lifetimes. It also tries to figure how much they cost on certain grids. One way of doing this is to look at what Lazard calls the “cost of firming intermittency” or “levelized firming costs.” This is essentially looking at what it costs to bring solar, solar and storage, and wind and storage onto actual grids considering their ability to perform when the grid is most stressed.
This measure tries to refine LCOE to give a sense of how various forms of energy generation compare to gas plants in real world circumstances, not just as a financial construct. This is not a perfect, real-world comparison — gas capacity needs to be “firmed” as well, as it’s not always entirely available at times of peak need — but at least it gives an idea of how these resources actually function in a real-world grid.
Even with firming costs, “renewables remain broadly cost-competitive,” the report concludes.
Not surprisingly, some of the most dramatic costs are in America’s most troubled electricity market, PJM Interconnection. The unsubsidized cost of firming intermittency for solar and storage is $167 per megawatt-hour, compared to $150 in Texas or $115 in California. That’s also compared to a $129 per megawatt-hour at the high end for conventional combined cycle gas plants in PJM.
PJM is notorious for its inability to bring on new resources quickly and its strict standards for accrediting the contribution of storage and renewables to grid stability.
While the Lazard authors explicitly caution that it doesn’t measure what the“total system costs are for 1 MWh of incremental electricity” and can’t say “the optimal mix of renewables, conventional generation and storage,” it does conclude that “firming costs and dispatchability are increasingly critical for comparing resources on a more complex grid.”
In short, no matter what ends up on the grid, grid planners will have to think carefully about how to make sure it’s reliable and works in concert with what’s already there.
Timber companies think of them as pests, but new research indicates that stands of the slender tree can act as barriers against raging flames.
Colorado’s Aspen Acres Fire is named after a quiet RV campground located high in the San Isabel Mountains, about a five-hour drive due southeast of the state’s better-known Aspen. Both places, however, are named after the iconic deciduous tree known for its golden leaves in the fall. While the start of monsoon season may yet prevent the Aspen Acres Fire — the seventh-largest in Colorado’s history — from joining Utah’s Babylon Fire as the second 100,000-acre “megafire” of the season, the conflagration has been aided in its rampage not by aspens, but rather by dead, downed, and blighted ponderosa pines, spruce, and Douglas firs. The wildfire has now burned over 98,000 acres and nearly 300 homes, and is only 36% contained due to steep terrain that has hampered firefighting efforts, along with extreme drought conditions and beetle infestations that have greatly degraded the forest health of the region.
But what about its aspens? Though the extent of the damage at the campground remains unknown, according to a recent study of Populus tremuloides, Colorado’s iconic golden trees could be one of the keys to more wildfire-resistant forests in the future.
Flavie Pelletier, a recent PhD graduate of McGill University’s Natural Resource Sciences program, told me she first became interested in aspens while working as a tree planter in British Columbia. “The historical assumption on aspen is that stands are very good at stopping fire progression. But the paradox is that if you take an aspen by itself, it’s going to burn at high severity,” Pelletier, who published her findings in Forest Ecology and Management, told me.
By creating near-real-time maps of fires using satellites and comparing them against the Canadian Forest Service’s newly available maps of dominant tree species in the boreal, Pelletier and her colleagues discovered that aspen were almost two and a half times more common at the perimeter of a burned area than inside it. The finding suggests that despite the flammability of a single aspen with its thin bark, stands of aspen act as a kind of barrier when wildfire ran up against them, likely because they lack the flammable resins of conifers and their high foliage helps force running crown fires back toward the ground. Pine and spruce, by contrast, showed a near-zero or even negative effect.
When aspen stands did burn, Pelletier found they did so more slowly: A tree cover of 50% aspen burned at about 224 hectares per day, compared to 717 hectares per day in areas where aspen made up less than 10% of the cover. That’s the equivalent of about 1,000 FIFA-regulation soccer pitches per day in places where aspen are sparser — like Aspen Acres.
Even more surprising, though, was that the pattern held true in the early season, when the trees are still twiggy and have yet to grow their moisture-filled leaves, and despite the severity of fire weather. “Aspen still showed resilience even when the fire weather was very intense, [like in 2023, when] we had all the fires,” Pelletier said.
But she was also the first to admit that seasons are getting more extreme, and that there’s no guarantee the pattern will hold for the next 10 or 20 years.
Pelletier was reluctant to make a policy recommendation based on her research, noting that she’s not a forest manager. But in Alberta and British Columbia, timber companies spray hundreds of thousands of acres of timber with glyphosate, an herbicide, to kill off aspens because the trees outcompete the more commercially valuable conifers. Her findings are “a big argument to stop the spreading of herbicides because you’re increasing the risk of fire in your forest by removing aspen,” Pelletier said.
Despite her hesitation, Pelletier is explicit in her paper about one thing: that aspens “should be encouraged — specifically around key landscape positions, such as population centers” — given that they are a proven means of hardening the wildland-urban interface against wildfires. It might be too late for the idyllically named Aspen Acres, of course; any of the aspens that once drew tourists to the area are likely now ash.
But this not be Colorado’s last fire, either.