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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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Current conditions: A sharp dip in the jet stream will channel Arctic air from the Plains to the Northeast, with snow expected this weekend in Minneapolis, Chicago, and Detroit • Northern California is bracing for potential power outages amid winds of up to 90 miles per hour • Temperatures of about 91 degrees Fahrenheit in Jerusalem just broke records for November temperatures dating back nearly 150 years.

The world’s most important climate summit is set to begin. The first phase of the 30th Conference of the Parties to the United Nations Framework Convention on Climate Change — better known as COP30 — is slated to kick off this morning with a Leaders’ Summit that will bring together 143 delegations, including 57 heads of state and 39 ministers in Belém, a bayside city near Brazil’s northern coast. Negotiations over how to tighten ways to implement global emissions rules and hasten the speed of cuts are set to begin officially on Monday.
Taking place against the backdrop of the United States’ withdrawal from climate negotiations and pullback of ambition from many other countries, the confab comes as the latest modeling from Rhodium Group consultancy shows the world is now on track to blow past the Paris Agreement’s 2-degree Celsius target but avoid the cataclysmic warming once forecast. The data projects the world will warm between 2 and 3.9 degrees above pre-industrial averages by the end of the century. As Heatmap’s Emily Pontecorvo wrote this week, that range is largely unchanged from Rhodium’s 2023 forecasts, suggesting that, “in the long run,” the Trump administration’s policies “might not mean much for the climate’s trajectory.” COP30 President André Corrêa do Lago on Wednesday unveiled a $1.3 trillion climate finance roadmap to fulfill promises made at last year’s meeting in Azerbaijan, but told reporters that “there is no plan” for the roadmap even to be discussed at the summit, let alone formally adopted, according to Climate Home News.
Stardust Solutions, the U.S.-based, Israeli-led geoengineering startup just raised $60 million to commercialize technology to reflect the sun’s heat back into space, has quietly begun lobbying the U.S. government for contracts. In the first quarter of this year, the company hired law firm Holland & Knight to start appealing to Congress, but didn’t disclose its efforts “due to a clerical error,” the lobbyist told E&E News on Wednesday.
To many scientists, geoengineering is too dangerous to even study, posing a moral hazard to decarbonization by offering a temporary solution to the effects of warming. But, as I reported exclusively in this newsletter in September, more than 100 scientists — including former President Joe Biden’s science adviser — signed onto a public letter calling for a publicly-accountable research program to start now in case global warming gets bad enough that a country or corporation tries to unilaterally carry out geoengineering before it’s fully understood. The emergence of a major commercial contender such as Stardust suggests the tides are turning in favor of the technology. As Heatmap’s Robinson Meyer reported last month in a scoop about Stardust’s fundraising, the company claims its technology will be ready to go by the start of the next decade.
Meanwhile, data center companies are sparking a boom in Beltway influence-peddling. The four largest cloud providers — Amazon, Microsoft, Google, and Meta — have all “reported tens of millions of dollars in federal lobbying in 2025 alone,” according to a new analysis from the federal records nonprofit OpenSecrets. The number of lobbyists per data center has also increased. Meta hired 21 more lobbyists this year than last year, and ChatGPT-maker OpenAI increased its stable of lobbyists nearly sevenfold since 2023.
The lobbying push comes amid mounting backlash. A Heatmap poll published in September found that only 44% of Americans would welcome a data center near their homes.
Taiwan this week took what may be its most significant step yet toward restarting its nuclear reactors. In May, the island became one of the only countries in world history to abandon nuclear power entirely after shutting down its final reactor. The move rendered the self-governing republic, which China claims as a breakaway territory despite the Communist Party never ruling there, almost entirely dependent on imported fossil fuels for its energy. Electricity prices are soaring — the domestic rates the Taiwan Semiconductor Manufacturing Company, the country’s national industrial champion, now pays are the highest of any of its global operations — and outages have grown. Worse yet, Taiwan is now vulnerable to blockades by the Chinese military that could weaponize blackouts in much the same way Russia has against Ukraine. Despite this, the ruling Democratic Progressive Party in Taiwan, which nominally supports independence from China, has opposed nuclear power since its inception. While Taiwanese President Lai Ching-te struggled to halt the final shutdown in the year after he took office, his administration has expressed an openness to nuclear power again.
On Wednesday, the state-owned utility Taipower submitted its assessment of how to restart shuttered reactors to the Ministry of Economic Affairs. In a referendum in August on whether Taiwan should restart its most recently closed plant, a majority of voters who cast ballots approved the measure, yet the plebiscite failed because it did not attract a large enough share of eligible voters. But the United Daily News reported that Taipower’s top boss said “there are opportunities and conditions” for restarting not just that last plant but the country’s second station, too. The news comes just days after Spain, the only country still pursuing a nuclear phaseout plan, officially started the paperwork to reconsider the policy, as I reported in Monday’s newsletter.
The new generation of geothermal startups promising to use novel drilling techniques to expand the energy source’s footprint get a lot of attention. But Ormat Technologies dominates the U.S. industry with conventional operations. In August, Ormat entered a strategic partnership with one of the next-generation companies, Sage Geosystems, in a move analysts told me at the time amounted to the giant in the space picking a “winner” among the newcomers. Yet Ormat’s latest earnings suggest it’s found a new area for growth: storage. Revenue from energy storage deals skyrocketed 108% year over year thanks to good weather conditions and higher capacity prices in the PJM Interconnection, the nation’s largest grid. The company said it expects annual growth in the sector of up to 17% over the next three years, Utility Dive reported.
Depending on how you feel about arachnids, this will either horrify you or delight you. Scientists just discovered the world’s biggest spider web, a subterranean “megacity” spanning nearly 1,080 square feet in a sulfur cave on the Albania-Greece border. Attached to a wall near the cave’s entrance, the colony — much like our own urban dwellings — has a large and diverse population. Roughly 69,000 Tegenaria domestica, known as the domestic house spider, call the web network home, along with 42,000 Prinerigone vagans spiders. Researchers believe this to be the first documented case of a colonial web formation for both species.
But this might all be moot thanks to the “major questions doctrine.”
Could President Trump’s expansive interpretation of the International Emergency Economic Powers Act empower a future president to, gasp, tariff carbon intensive goods?
That’s the terrifying prospect Justice Neil Gorsuch, a staunch conservative who often votes in line with Trump and his administration’s positions, raised to Solicitor General D. John Sauer in Wednesday’s oral arguments in the federal court case seeking to throw out Trump’s tariffs.
In a series of questions designed to draw out what limits Sauer thought existed on executive power, Gorsuch asked, “Could the president impose a 50% tariff on gas-powered cars and auto parts to deal with the unusual and extraordinary threat from abroad of climate change?” (This echoed the language of the statute the Solicitor General cited to justify the tariffs.)
“It’s very likely that could be done,” Sauer conceded.
“I think that would have to be the logic of your view,” Gorsuch replied.
“Obviously this administration would say that’s a hoax, this is not a real crisis,” Sauer said.
“I’m sure you would,” Gorsuch said to chuckles.
“But that would be a question for Congress, under our interpretation, not the courts,” Sauer said.
Gorsuch’s questioning touched on the “major questions doctrine,” first propounded in the court’s 2022 opinion in West Virginia v. Environmental Protection Agency. In that case, which resulted in the court striking down the Obama-era Clean Power Plan power plant regulations, the conservative majority argued that “given both separation of powers principles and a practical understanding of legislative intent, the agency must point to ‘clear congressional authorization’ for the authority it claims,” which it claimed the rules lacked.
In a note to clients following the emissions rules case, the white shoe law firm Davis Polk wrote that the majority opinion “does not provide guidance for applying the major questions doctrine in future cases,” but noted that a concurrence authored by Justice Gorsuch “attempted to provide such guidance for future cases.” In said concurrence, Gorsuch wrote that the major questions doctrine could be invoked when the executive branch is dealing with a question of “great political significance” or “a significant portion of the American economy.”
Hmm!
Some progressives flagged this aspect of the tariffs case as it worked its way through the courts, pointing out that it could call into question powers that future presidents may want to use to implement expansive industrial policy, including climate policy. Some of the broader legal arguments against the tariffs, Todd Tucker of the progressive Roosevelt Institute wrote in a brief, “tilt the scales overwhelmingly against progressive priorities.”
“Limits on Trump today will bind future presidents tomorrow. This could include centrists, progressives, MAGA types, or traditional conservatives, who will need or want robust executive tools to address ruinous competitiveness or climate emergencies.”
But in pursuit of their clients’ interests, advocates for striking down the tariffs were more than happy to pick up the thread dropped by Gorsuch to make libertarian-leaning arguments about presidential powers.
“It is simply implausible that in enacting” the International Emergency Economic Powers Act, the law Trump has used to justify his retributive import taxes, “Congress handed the president the power to overhaul the entire tariff system and the American economy in the process, allowing him to set and reset tariffs or any and every product from any and every country at any and all times,” Neal Katyal, the lawyer arguing on behalf of a beer and wine distributor and a longtime figure in Democratic legal circles, said in his oral argument.
Perhaps seeking to appeal to the Republican majority on the court, Katyal returned to Justice Gorsuch’s climate change example, arguing that “if the government wins, another president could declare a ’climate emergency’ and impose huge tariffs without floors or ceilings, as Justice Gorsuch said.”
“My friend’s answer,” Katyal said, referring to Sauer, “is, ‘This administration would declare it a hoax.’ The next president may not quite say that.”
Many legal experts thought that the administration got the worse of the oral arguments and questioning of the attorneys, with conservative Justices Gorsuch and Amy Coney Barrett and Chief Justice John Roberts all asking skeptical questions of Sauer, while Justices Clarence Thomas and Samuel Alito repeatedly threw the White House argumentative lifelines, including, in Alito’s case, suggesting other laws that could justify the tariffs.
Alito even gently mocked Katyal, a Democrat who served as acting solicitor general in the Obama administration, for blatantly using conservative-tinged legal arguments about the scope of executive authority over the economy.
“I wonder if you ever thought that your legacy as a constitutional advocate would be the man who revived the non-delegation argument,” referring to the idea that certain powers are too much akin to lawmaking to delegate to the executive branch, which in theory could vastly restrict the authority of regulators.
But Katyal resisted the implied contradiction and persisted in targeting the right wing of an already conservative Supreme Court.
“Heck yes,” Katyal said. “I think Justice Gorsuch nailed it on the head when saying that when you’re dealing with a statute that is this open-ended — unlike anything we’ve ever seen.”
On Massachusetts’ offshore headwinds, Biden’s gas rules, and Australia’s free power
Current conditions: The Pacific Northwest is getting blasted with winds of up to 70 miles per hour • Heavy snow is coming this week for the higher elevations in New England and upstate New York • San Cristóbal de La Laguna in the Canary Islands saw temperatures surge to 95 degrees Fahrenheit.

Democratic candidates swept to victory in key races with implications for climate change on Tuesday night. In Virginia, Democrat Abigail Spanberger — who vowed to push forward with offshore wind, new nuclear reactors, and fusion energy — seized the governor’s mansion in the first major race to be called after polls closed. In New Jersey, Democrat Mikie Sherrill, who campaigned on building new nuclear plants and pressing the state’s grid operator, PJM Interconnection, to cut electricity prices, trounced her Republican opponent. In New York City, Democrat Zohran Mamdani, who said little about energy during his campaign but came out in the last debate in favor of nuclear power, easily beat back his two rivals for Gracie Mansion. Yet the Georgia Public Service Commission's incumbent Republican Tim Echols lost his race against Democrat Alicia Johnson, a defeat for a conservative who championed construction of the only two nuclear reactors built from scratch in modern U.S. history. In what one expert called a sign of a “seismic shift” on the commission, Peter Hubbard, another Democrat running to flip a seat on the commission, also won.
At a moment when the Trump administration is “disassembling climate policy across the federal government,” Heatmap’s Emily Pontecorvo wrote, “state elections are arguably more important to climate action than ever.”
A federal judge in Washington ruled Tuesday that the Trump administration can reconsider the Biden-era approval of SouthCoast Wind off the coast of Nantucket, Massachusetts. The decision, reported in The New York Times, is a setback for the joint venture between EDP Renewables and Engie, and handed the White House a victory in what we’ve called here the administration’s “total war on wind.” Judge Tanya S. Chutkan of the U.S. District Court for the District of Columbia ruled that the project developers would not “suffer immediate and significant hardship” if the Department of the Interior’s Bureau of Ocean Energy Management were allowed to reevaluate the project’s construction and operation permits.
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Meanwhile, the U.S. Court of Appeals for the D.C. Circuit upheld Biden-era Department of Energy efficiency rules for gas-fired residential furnaces and commercial water heaters in a ruling that rejected the gas industry’s challenge on Tuesday. “Overall, we find that DOE’s economic justification analysis and conclusions were robust,” the panel ruled, according to Bloomberg Law. The decision will maintain the status quo of how the agency enforces energy efficiency rules for the appliances. Under standards updated in 2021 and 2023, the Biden-era bureaucrats proposed raising efficiency levels to 95% for furnaces and using condensing model designs to heat water.
White House budget officials pressed the Environmental Protection Agency to expand its rollback of tailpipe regulations this summer as the agency sought to repeal the foundational policy that undergirds federal climate rules, E&E News reported. Documents the green newswire service obtained showed the White House Office of Management and Budget pushed the environmental regulator to weaken limits on vehicular pollution, including soot and smog-forming compounds in addition to planet-heating carbon. The EPA initially pushed back, but the documents revealed the staffers at OMB demanded the agency pursue a more aggressive rollback.
Australia launched a new plan to force energy companies to offer free electricity to households during the day to use excess solar power and push the grid away from coal and gas. The policy, called the “Solar Sharer” plan, aims to take advantage of the country’s vast rooftop solar panels. More than 4 million of Australia’s 10.9 million households have panels, and the capacity has overtaken the nation’s remaining coal-fired power stations. The proposal, the Financial Times reported, would also extend the benefits of distributed solar resources to the country’s renters and apartment dwellers.
For years, nuclear scientists have dreamed of harnessing atomic energy from thorium, potentially shrinking radioactive waste and reducing the risk of weapons proliferation compared to uranium. In the West, that has remained largely a dream. In China, however, researchers are vaulting ahead. This week, Chinese scientists announced a major breakthrough in converting thorium to uranium in a reactor. “This marks the first time international experimental data has been obtained after thorium was introduced into a molten salt reactor, making it the only operational molten salt reactor in the world to have successfully incorporated thorium fuel,” Shanghai Institute of Applied Physics of the Chinese Academy of Sciences said in a statement.