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If you’re of a certain age, you probably remember the hole in the ozone layer. Like Joseph Kony and Livestrong wristbands, the obsession over O3 now feels like a cultural artifact, thanks to ozone depletion being one of the rare success stories of international environmental cooperation. Since the world banned chlorofluorocarbons under the Montreal Protocol in 1987, the holes over the North and South poles have steadily recovered.
Today, if you hear about “ozone” at all, it’s much more likely to be from an air quality alert on your phone. Unlike the stratospheric ozone that we were all so concerned about in the 1980s and 1990s, which makes up a protective layer around the planet that insulates us from the sun’s cancer-causing ultraviolet rays, “tropospheric” or “ground-level” ozone is mainly man-made. In fact, when people throw around the word “pollution,” what they’re probably talking about is ground-level ozone, which is created by a chemical reaction between nitrogen oxides (highly reactive gases produced by burning fuels) and volatile organic compounds (organic compounds that easily evaporate under normal environmental conditions and can be found in vehicle exhaust as well as scented personal care products like deodorants, lotions, and bug sprays), plus sunlight. This chemical reaction usually occurs when cars, refineries, power plants, and other industrial sources emit pollutants into the environment during a hot, clear day. You probably know the result by its other name: smog.
Ozone is a climate issue not just because it is yet another concerning consequence of burning fossil fuels. According to some estimates, high levels of ground-level ozone pollution could grow in frequency by three to nine additional days per year by 2050 because of the gas’s close relationship with intense sunlight and high temperatures. While ozone dissipates fairly quickly once those conditions go away, it can build up while they last. Hot days, which are increasing in the U.S., also coincide with weak winds and stagnant air — conditions that allow ozone to accumulate in one place.
When the temperatures start to rise, here’s what you need to know and what you can do to protect yourself and others from ozone pollution.
Different pollutants cause concern at different concentrations. The Air Quality Index is designed so that, in theory, a level of “100” corresponds to the point at which people in sensitive populations might start to be affected by the pollutant in question. (To learn more about how the AQI is calculated, you can read our explainer here).
That said, “The evidence has clearly been increasing that lower levels of ozone — levels well below the current standard of 70 parts per billion — are causing more health impacts,” Katherine Pruitt, the national senior director of policy at the American Lung Association, which is campaigning to strengthen the standard to 55 to 60 parts per billion, told me.
As Pruitt explained, ozone is a caustic irritant and can corrode metals. Breathing it in can cause inflammation in anyone, “from vulnerable children and elders to even the fittest elite athletes,” Pruitt said, adding that it is, “at some level, like getting a sunburn on your lungs.” Anyone who spends time outside is vulnerable to ozone, but the more sensitive groups — including children; the elderly; people with asthma, chronic heart disease, and other diseases; and pregnant women — are at a higher risk. They might already be paying more attention to the AQI levels in their area, and will potentially notice that they need to slow down and limit exertion during “yellow” or “orange”-level ozone events.
In the short term, ozone pollution can cause coughing, shortness of breath, and a lowered immune response, on top of aggravating any preexisting lung conditions or diseases. But Pruitt stressed to me that “living in places that have high levels of ozone day in and day out, for months and years, can cause respiratory diseases, nervous system disorders, metabolic disorders, reproductive problems, and mortality. It’s not just a cough and a wheeze on one bad air day.”
Ozone requires two main ingredients: the burning of fossil fuels and other chemicals, and sunlight. While ozone concentrations can be high in communities with a lot of industry and freeways nearby, ozone is “not really so much a roadway problem; it’s more of what we call an ambient air pollutant,” Pruitt said. Ozone can travel far away from where it was produced, in other words.
There are some rules of thumb, though. The places with the highest emissions and most appropriate atmospheric conditions for ozone pollution are “increasingly the western U.S. and the Southwest,” Pruitt said. The top four worst cities for ozone on the 2024 State of the Air report by the ALA were all in California, led by Los Angeles and Long Beach.
Since the passage of the Clean Air Act in 1963, other regions of the country have been doing much better, including the Southeast, mid-Atlantic, and Northeast. (Bangor, Maine, had the cleanest air in the report.)
Because ozone is so strongly related to sunlight, it does not cause indoor air pollution to the same extent as wildfire smoke (which, if you’re keeping score, is a PM2.5 pollutant). “Because it’s so reactive, it gloms onto your furniture and your walls and stuff, once it gets inside,” Pruitt said of ozone. To protect yourself, you can just stay indoors and run your air conditioner.
But what if you want or need to go out? Because ozone is a gas rather than a particle, HEPA filters and face masks won’t protect you. Instead, Pruitt said that you can time your errands, tend to your garden, and exercise when the sunlight is the weakest — mornings, especially, tend to be less demanding on the lungs during ozone events.
The Clean Air Act of 1963 requires the Environmental Protection Agency to review the national ambient air quality standards for ozone (as well as several other pollutants) every five years. “It almost never actually does it every five years” though, Pruitt said. “Sometimes advocates have to sue them to get them to move things along.” The EPA completed its last review in December 2020, with the Trump administration maintaining the 70 parts per billion standard set in 2015. Attacks on the Clean Air Act would likely resume if Trump retakes office.
Aside from agitating for stricter clean air standards, there are measures you can take to protect others from ozone events. The simplest is not to contribute any more nitrogen oxides and volatile organic compounds to the environment than you otherwise have to when ozone levels are high. Avoid driving or idling your car; top off your tank during the coolest parts of the day, such as after dark; minimize your electricity use; and set your air conditioner no lower than 78 degrees.
In the long term, reducing ozone pollution will mean “choosing greener products for cleaning and personal care, so that we’re not producing volatile organic compounds,” Pruitt told me. The National Oceanic and Atmospheric Administration previously found that in New York City in 2018, “about half” of the ambient volatile organic compounds it measured were produced by people, not vehicle exhaust. (Here’s a guide to reducing VOCs from your rotation.)
Additionally, “transitioning to zero-emission technologies so we're not burning fossil fuels” will help limit ozone pollution, Pruitt said. The difference can be pretty significant: A study from the University of Houston published earlier this month found that by switching to electric vehicles, New York and Chicago could prevent 796 and 328 premature pollution-related deaths per month, respectively. Counterintuitively, the study found that more EVs on the roads could increase mortality in Los Angeles due to a corresponding increase in secondary organic aerosols caused by complicated dynamics between nitrogen oxides and volatile organic compounds and the city’s unique geography. “This underscores the need for region-specific environmental regulations,” the authors said.
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More than $30 billion of clean energy investments are now on ice since Trump took office, according to new data from Wellesley College’s Big Green Machine.
America’s EV factory building boom is beginning to falter.
Since President Donald Trump took office, at least 34 factories or mineral refineries — totaling more than $30 billion in investment — have been paused, delayed, or canceled, according to a new report from researchers at Wellesley College who track the country’s clean energy manufacturing base.
“When you look at the projects that are slowing down, it’s all up and down the supply chain,” Jay Turner, an environmental studies professor who leads the database, told me.
Electric vehicle manufacturing projects are now being delayed or canceled at six times the rate that they were during the same period last year, he said.
The database, called the Big Green Machine, has data on EV and mineral factory activity going back to 2010, and has been actively tracking investment in the EV supply chain since 2022.
The news is not entirely bleak for the EV buildout, however. Another 68 projects have progressed in the past six months, according to Turner’s data. Those projects represent $24 billion in investment and more than 33,000 jobs.
At the same time, more than two dozen new projects have been announced in the past six months, but they are of a much smaller scale, the report finds. Taken together, the projects in this new wave add up to only $3 billion in investment — one-tenth of the $30 billion in projects that have been paused, delayed, or cancelled.
The Big Green Machine
The new data likely does not capture recent setbacks for the EV industry. Earlier this month, President Trump signed Republicans’ budget reconciliation bill, which will terminate all tax credits for buying or leasing an electric vehicle on September 30.
Turner told me that the slowdown was the predictable outcome of the Trump administration’s turn away from electric cars.
“In some ways, it’s exactly what we expected,” he said. “As concerns about the Inflation Reduction Act and bipartisan infrastructure law began last fall, we started to see projects slowing down. Since Trump was elected, those closures, cancellations, and delays have just ballooned.”
Particularly hard hit are projects located in distressed or fossil-fuel-dependent communities, as defined by the terms set out in the Inflation Reduction Act, he added. Facilities that depended on some kind of federal support or loan guarantee have also been especially likely to pause, he added.
The slowdowns have struck across the EV supply chain. Some battery factories have switched from producing lithium ion cells for vehicles to making large-scale batteries for the power grid. The new budget law, called the One Big Beautiful Bill Act, maintained tax incentives for installing grid-scale battery storage.
Mineral producers have also been affected. Li-Cycle paused work on mineral recycling plants in April, Turner said. A Canadian rare earth processing facility — one of the few such factories in North America — scaled back its ambitions this month. (“The data in our report is just the U.S., but when you add in Canada it’s more shocking how sharp the downturn has been,” Turner said.)
That follows other delays from last year. The Chicago-based company Anovion has continued to pause work on an $800 million facility in southwest Georgia that was slated to make synthetic graphite, which is essential for lithium ion battery anodes.
Last year, the chemicals company Albemarle delayed $1.3 billion in plans to build the country’s largest lithium refinery in South Carolina. “The economics just aren't there to build that plant,” Kent Masters, Albemarle’s CEO, told Reuters in May. China controls roughly three-quarters of the world’s lithium and synthetic graphite supply chains.
Despite its antagonism toward electric cars, the Trump administration has sought to prioritize some mineral projects. Earlier this month, the Pentagon announced a complex deal to invest in — and guarantee a buyer for the output of — a rare earths mine and processing facility on the California-Nevada border.
Whatever the cause of the slowdown, it isn’t limited to just electric cars. Total private manufacturing investment in the United States has leveled off and slightly fallen since October 2024.
On abandoning Antarctica, an EV milestone, and this week’s big earnings
Current conditions: Heavy rainfall in China has left at least 30 dead as forecasters predicts more days of downpours ahead • Severe thunderstorms are hitting the Midwest as a cold front suppresses the heat dome • The wildfires blazing across Canada are stretching into Alaska, with dozens of fires raging in the foothills of the Brooks Range.
Last year, oil giants Shell, ExxonMobil, and BP either abandoned their decarbonization goals or dialed down investments in green energy. Last week, the Financial Times also reported that the oil industry had put its effort to establish a net-zero emissions standard on pause as major companies quit the initiative. But at least one oil titan is doubling down on clean energy. On Monday, the Italian oil giant Eni said it expects its green business to rival revenues from oil and gas within a decade.
By 2035, CEO Claudio Descalzi told the FT, the operating profit “created by our new companies will balance what is coming from oil and gas, and in 2040 it will be more.” It’s a bullish bet. Earnings from Eni’s oil and gas business are still more than 10 times those from the biofuels and renewables divisions. While the company’s stock dipped by a little over 1% on Monday after the company reported its latest earnings, which beat analysts’ expectations and promised a $1.8 billion buyback, shares in Eni are up nearly 6% over the past month.
This is a big earnings week, with lots of upcoming announcements relevant for Heatmappers:
Tuesday:
Carrier
DTE Energy
Stellantis
Wednesday:
Microsoft
Meta
Rio Tinto
Hess
Entergy
Thursday:
Amazon
Shell
Southern Company
Air Products and Chemicals
TC Energy
Exelon
Xcel
Cameco
First Solar
ArcelorMittal
U.S. Steel
AES
Friday:
ExxonMobil
Chevron
Enbridge
Dominion
Brookfield Renewable Corporation
American researchers in Antarctica in 1955 set off across the ice from the icebreaker, USS Burton Island. Pictorial Parade/Archive Photos/Getty Images
In a shock to polar scientists, the National Science Foundation plans to cease operations of the United States’ only research ship capable of braving the farthest reaches of Antarctica in the Southern Ocean, the RV Nathaniel B. Palmer, Science magazine reported. Doing so would end 60 years of continuous operations of American icebreakers in Antarctica. More than 170 researchers sent a letter to the head of the NSF and Congress asking for the agency to reconsider.
The move comes amid heightened tensions on both poles as climate change brings radical changes to the planet’s ice caps. The Trump administration has taken a keen interest in the race to dominate the trade routes, military outposts, and natural resources becoming newly accessible in the Arctic, going as far as to pressure NATO ally Denmark to cede sovereignty of semi-autonomous Greenland the U.S. While the geopolitics of the uninhabited Antarctic have garnered less attention, similar dynamics are arising. China is boosting its investments in Antarctica and just opened its fifth research station. Russia has undermined attempts to inspect its bases there, which violates the Antarctica Treaty, an international agreement meant to ensure that no country can militarize the continent. China and Russia have also teamed up to tank new international protections on marine life.
The U.S. is on track to add 16,700 public fast-charging ports by the end of this year, according to InsideEVs. The effort — led by Tesla, ChargePoint, and EVgo — would represent 2.4 times the number of ports added in 2022. If the pace continues, the U.S. could have 100,000 public fast-charging ports by 2027. That’s nearing the 145,000 gas stations the U.S. operates for refueling internal combustion engine vehicles.
The milestone comes as EV sales are surging ahead of the September 30 deadline phasing out the $7,500 tax credits for electric cars Republicans set in President Donald Trump’s landmark tax law, the One Big Beautiful Bill. U.S. Even though Tesla sales dropped, U.S. EV sales overall surged 10% in the last quarter, led by GM’s new offerings.
The State of New York announced its first bulk solicitation for energy storage, putting out a bid for 3 gigawatts of batteries. The projects will be “credited and compensated based on the operational availability they achieve in each month over the course of” contracts ranging from 15 to 25 years. Governor Kathy Hochul said the bid highlighted “New York’s ongoing commitment to strengthening our grid, ensuring the state continues to have a more affordable and reliable electricity system now and well into the future.”
It’s just the latest big energy announcement from the state. Last month, Hochul ordered the New York Power Authority — the nation’s second-biggest government-owned utility after the federal Tennessee Valley Authority — to build the state’s first new nuclear power station since the 1980s. As Heatmap’s Matthew Zeitlin pointed out, the project mirrors the atomic ambitions of other government-owned utilities. Ontario plans to build what could be the nation’s first small modular reactors, using GE-Hitachi Nuclear Energy’s design. The TVA is slated to build the second set of those same reactors. But as I reported over the weekend for New York Focus, one of the state’s biggest utilities is lobbying Albany to consider the same kind of large-scale reactors that were just completed in Georgia, the Westinghouse AP1000.
Last month, solar panels delivered the largest share of the European Union’s electricity for the first time, narrowly eclipsing nuclear power, according to data from Ember. Yet this month, industry projections put the bloc on track for the first decline in solar growth since 2015. The EU is set to deploy 64.2 gigawatts this year, down from 65.1 gigawatts in 2024. The installations are set to help the bloc exceed the European Commission’s 2025 solar target of 400 gigawatts, bringing the total to 402 gigawatts by the end of the year.
But if the trend continues, Europe may fall roughly 4% short of its 2030 goal of 750 gigawatts of solar, installing just 723 gigawatts. That may not sound like a lot, but Dries Acke, the deputy chief executive of SolarPower Europe, said “the symbolism is big. Market decline, right when solar is meant to be accelerating, deserves EU leaders’ attention.” The industry group blamed the downturn on declines in residential solar as feed-in tariff schemes waned in Austria, Belgium, Czechia, Hungary, Italy, and the Netherlands. But corporate deals for solar power also dropped 41% between the first and second quarters of this year. Over the weekend, meanwhile, the EU signed a major trade deal with the Trump administration, promising to ramp up purchases of liquified natural gas and oil.
Scientists at the University of California at Davis used artificial intelligence to engineer proteins to boost the immune systems of plants, helping the flora fight off bacterial threats. The research, published Monday in the journal Nature Plants, opens the door to new ways of protecting crops such as tomatoes and potatoes from disease. “Bacteria are in an arms race with their plant hosts,” Gitta Coaker, the study’s lead author and a professor in the Department of Plant Pathology, said in a press release.
Half of all Americans are sweating under one right now.
Like a bomb cyclone, a polar vortex, or an atmospheric river, a heat dome is a meteorological phenomenon that feels, well, a little made up. I hadn’t heard the term before I found myself bottled beneath one in the Pacific Northwest in 2021, where I saw leaves and needles brown on living trees. Ultimately, some 1,400 people died from the extreme heat in British Columbia, Washington, and Oregon that summer weekend.
Since that disaster, there have been a number of other high-profile heat dome events in the United States, including this week, over the Midwest and now Eastern and Southeastern parts of the country. On Monday, roughly 150 million people — about half the nation’s population — faced extreme or major heat risks.
“I think the term ‘heat dome’ was used sparingly in the weather forecasting community from 10 to 30 years ago,” AccuWeather senior meteorologist Brett Anderson told me, speaking with 36 years as a forecaster under his belt. “But over the past 10 years, with global warming becoming much more focused in the public eye, we are seeing ‘heat dome’ being used much more frequently,” he went on. “I think it is a catchy term, and it gets the public’s attention.”
Catching the public’s attention is critical. Heat is the deadliest weather hazard in the U.S., killing more people annually than hurricanes, floods, tornadoes, or extreme cold. “There is a misunderstanding of the risk,” Ashley Ward, the director of the Heat Policy Innovation Hub at Duke University, told me. “A lot of people — particularly working age or younger people — don’t feel like they’re at risk when, in fact, they are.”
While it seems likely that the current heat dome won’t be as deadly as the one in 2021 — not least because the Midwest and Southeastern regions of the country have a much higher usage of air conditioning than the Pacific Northwest — the heat in the eastern half of the country is truly extraordinary. Tampa, Florida reached 100 degrees Fahrenheit on Sunday for the first time in its recorded history. Parts of the Midwest last week, where the heat dome formed before gradually moving eastward, hit a heat index of 128 degrees.
Worst of all, though, have been the accompanying record-breaking overnight temperatures, which Ward told me were the most lethal characteristics of a heat dome. “When there are both high daytime temperatures and persistently high overnight temperatures, those are the most dangerous of circumstances,” Ward said.
Although the widespread usage of the term “heat dome” may be relatively new, the phenomenon itself is not. The phrase describes an area of “unusually strong” high pressure situated in the upper atmosphere, which pockets abnormally warm air over a particular region, Anderson, the forecaster, told me. “These heat domes can be very expansive and can linger for days, and even a full week or longer,” he said.
Anderson added that while he hasn’t seen evidence of an increase in the number of heat domes due to climate change, “we may be seeing more extreme and longer-lasting heat domes” due to the warmer atmosphere. A heat dome in Europe this summer, which closed the Eiffel Tower, tipped temperatures over 115 degrees in parts of Spain, and killed an estimated 2,300 people, has been linked to anthropogenic warming. And research has borne out that the temperatures and duration reached in the 2021 Pacific Northwest heat dome would have been “virtually impossible without human-caused climate change.”
The link between climate change and heat domes is now strong enough to form the basis for a major legal case. Multnomah County, the Oregon municipality that includes Portland, filed a lawsuit in 2023 against 24 named defendants, including oil and gas companies ExxonMobil, Shell, and BP, seeking $50 million in damages and $1.5 billion in future damages for the defendants’ alleged role in the deaths from the 2021 heat dome.
“As we learned in this country when we took on Big Tobacco, this is not an easy step or one I take lightly, but I do believe it’s our best way to fight for our community and protect our future,” Multnomah County Chair Jessica Vega Pederson said in a statement at the time. The case is now in jeopardy following moves by the Trump administration to prevent states, counties, and cities from suing fossil fuel companies for climate damages. (The estate of a 65-year-old woman who died in the heat dome filed a similar wrongful death lawsuit in Seattle’s King County Superior Court against Big Oil.)
Given the likelihood of longer and hotter heat dome events, then, it becomes imperative to educate people about how to stay safe. As Ward mentioned, many people who are at risk of extreme heat might not even know it, such as those taking commonly prescribed medications for anxiety, depression, PTSD, diabetes, and high blood pressure, which interfere with the body’s ability to thermoregulate. “Let’s just say recently you started taking high blood pressure medicine,” Ward said. “Every summer prior, you never had a problem working in your garden or doing your lawn work. You might this year.”
Air conditioning, while life-saving, can also stop working for any number of reasons, from a worn out machine part to a widespread grid failure. Vulnerable community members may also face hurdles in accessing reliable AC. There’s a reason the majority of heat-related deaths happen indoors.
People who struggle to manage their energy costs should prioritize cooling a single space, such as a bedroom, and focus on maintaining a cool core temperature during overnight hours, when the body undergoes most of its recovery. Blotting yourself with a wet towel or washcloth and sitting in front of a fan can help during waking hours, as can visiting a traditional cooling center, or even a grocery store or movie theater.
Health providers also have a role to play, Ward stressed. “They know who has chronic underlying health conditions,” she said. “Normalize asking them about their situation with air conditioning. Normalize asking them, ‘Do you feel like you have a safe place to go that’s cool, that you can get out of this heat?’”
For the current heat dome, at least, the end is in sight: Incoming cool air from Canada will drop temperatures by 10 to 20 degrees in cities like Philadelphia and Washington, D.C., with lows potentially in the 30s by midweek in parts of New York. And while there are still hot days ahead for Florida and the rest of the Southeast, the cold front will reach the region by the end of the week.
But even if this ends up being the last heat dome of the summer, it certainly won’t be in our lifetimes. The heat dome has become inescapable.