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A new report shared exclusively with Heatmap documents failures of transparency and governance at the Greenhouse Gas Protocol.

It is something of a miracle that tens of thousands of companies around the world voluntarily report their greenhouse gas emissions each year. In 2025, more than 22,100 businesses, together worth more than half the global stock market, disclosed this data. Unfortunately, it’s an open secret that many of their calculations are far off the mark.
This is not exactly their fault. To aid in the tedious process of tallying up carbon and to encourage a basic level of uniformity in how it’s done, companies rely on standards created by a nonprofit called the Greenhouse Gas Protocol. The group’s central challenge is ensuring that its standards are both credible and feasible — two qualities often in tension in greenhouse gas accounting. The method that produces the most accurate emissions inventory may not always be feasible, while the method that’s easy to implement may produce wildly inaccurate results.
Critics have long faulted the Protocol for allowing companies to look far better on paper than they do to the atmosphere. In 2022, the group began in earnest to try and fix this, starting with an overhaul of its governance. It created a new Independent Standards Board that would oversee and approve updates to each of its accounting rules, and later convened a series of technical working groups to develop the substance of those updates. One such group was updating the method for how companies should account for their electricity use. Another was focused on supply chain emissions.
The working groups would meet regularly to put together proposals and then submit those proposals to the Independent Standards Board for approval. A separate steering committee would then review the board’s decision to ensure that the Protocol’s overall principles had been followed throughout the process and make the final call.
The new structure was meant to “further bolster the credibility and integrity of these standards,” the Protocol wrote. The overhaul was especially timely as governments around the world, including those of the European Union and the state of California, were taking steps to adopt the Protocol’s standards in their own mandatory climate disclosure rules.
But what started as a laudable effort to improve transparency and accountability has turned rancid, some of the participants told me. Scientists are being pitted against industry representatives. Proposals, voting records, and other key documents are being kept from the public eye. Decisions made behind closed doors are going undocumented and undisclosed, kept secret even from the working group members who have devoted significant unpaid time to the cause of developing stronger standards.
These issues are broadly illustrated by the experience of Kate Dooley, a member of the GHG Protocol’s technical working group on forest carbon accounting. Dooley is a political scientist and lecturer at the University of Melbourne’s School of Geography, Earth and Atmospheric Sciences who has worked on issues related to forest carbon accounting for roughly two decades. She joined the 17-person working group in December 2024; the group’s assignment was to resolve a contentious debate over how companies that own or control forests or use forestry products in their supply chains should account for carbon emissions related to their harvesting, land management, and wood product purchases. The group included academics like Dooley, industry representatives from companies such as IKEA, and experts from non-profits including the Natural Resources Defense Council and the American Forest Foundation.
After six months of meetings, however, the members could not reach a consensus. One of the key reasons forest carbon accounting is difficult is that forests can both emit carbon and remove it from the atmosphere. Determining what proportion of those removals are a result of human activity versus what would happen naturally gets complicated quickly. The stakes were high, because even though the GHG Protocol standards are portrayed as neutral accounting exercises, small decisions about how this accounting is performed can create big shifts in incentives for how companies operate.
The forestry group considered two main approaches. One is called the “managed land proxy,” or MLP, and it is the method countries use to report their emissions to the United Nations. This method would allow companies to include all of the carbon that’s being sequestered on their lands in their greenhouse gas inventory. A timber company that cuts down trees, for instance, would count both the emissions released from logging as well as the carbon sequestered by the remaining tree stands and calculate a net result.
The major criticism of this approach is that it’s easy to game and leads to unintuitive results, where forest product companies come out looking like they are removing far more carbon than they are releasing. The method would also enable companies to use the average emissions and removals of an entire region in their calculations, rather than the specific logging and forest management practices of their supply source. Another risk is that companies could simply buy up additional forest land to reduce their emissions on paper while changing nothing about their business practices.
Proponents of this method put forward what they framed as a compromise, called “MLP+,” which attempted to put some guardrails around these issues. Regardless, the scientists in the group argued that it was scientifically incorrect to attribute all forest carbon sequestration that happens within a given tract of land to a company when that carbon removal may be the result of unrelated factors such as elevated CO2 in the air from climate change, or that a previous owner had cut down trees that were now growing back.
The alternative method that the scientists, including Dooley, put forward is called “activities-based accounting.” Rather than take credit for all forest growth, this method would require landowners to account for the growth that would have occurred without human interference and subtract it from their estimate of carbon removals. This method would be more difficult and require further work to fine-tune. It would also have the effect of making corporate forest emissions look much higher on paper.
In a final vote between two proposals, the members split 8 to 7 in favor of MLP+, with two sitting out the vote. The group delivered both proposals to the Independent Standards Board for consideration last spring, but the board could not reach a consensus, either. Ultimately, the organization decided to finalize the land sector standard in January 2026 without any guidance for forest carbon accounting, advising companies to go with whatever method they wanted as long as they disclosed how they did it. It noted that it would soon issue a request for information to gather more stakeholder input on the issue.
By the end of the working group process, the internal dynamics had grown combative. Dooley and other scientists in the group argued that certain scientific papers supported their rebuke of MLP. But another member, Nathan Truitt, the executive vice president of climate funding at the American Forest Foundation, argued that the same papers made the opposite point.
“It was this weird, Kafka-eque development,” Dooley said. She responded to the entire group with a long email detailing the last 20 years of debate on the subject, she told me. “I think in that email I accused [Truitt] of industry bias, because there was no other explanation for what he was doing,” she said.
The American Forest Foundation provides technical and financial support to help private landowners sustainably manage their forests. Truitt, for his part, characterized the atmosphere in the working group as toxic. He told me that the scientists did not adequately explain to him why they thought he was interpreting the papers incorrectly. He noted that the foundation is a mission-based nonprofit, and less than 5% of its revenues comes from the forest products industry, but the organization does believe in supporting healthy forest markets. “If landowners can’t generate revenue from appropriate forest management, there won’t be forest there very long,” he said.
But Dooley’s concerns were bigger than just interpersonal challenges. She didn’t understand why none of the explanatory memos or official proposals produced by the working group had been published to the Protocol’s website, when similar documents produced by the other working groups had been made public. (Truitt also was not aware of this until I reached out to him, and was surprised to learn it.)
Initially, the scientists’ full memo on their approach was not even shown to the Independent Standards Board; Dooley told me she had to write to the head of the board and ask that it be shared. It was also odd to her that there was no follow-up from the Independent Standards Board after the proposals had been submitted.
Perhaps one of the strangest elements of the process was that the Greenhouse Gas Protocol had conducted a real-world pilot program of MLP prior to the formation of the working group. There was public documentation of the pilot’s existence, but the outcomes were not published, nor were they shared with the group. Dooley said that someone who had viewed the results told her they decidedly proved the problems with MLP. Her understanding was that almost all of the forest product companies that participated reported huge amounts of net carbon removals, making them appear to have a beneficial impact on the climate, contributing nothing to global emissions. “To me, it’s inexplicable why that pilot study wasn’t shown,” she said.
Months later, in January 2026, Dooley received a document that reframed her experience. It was a formal complaint made by Truitt the previous April that challenged the scientists’ expertise and impartiality, she told me. She also learned that following the complaint, the Independent Standards Board solicited opinions from additional outside scientists on the two proposals. She was shocked that she had been kept in the dark as this was going on.
Dooley emailed the head of the board and other leaders at the Protocol to ask why she and the other scientists weren’t told about the complaint or given a chance to respond. “We write to express concern that this complaint was not initially communicated to those concerned, and to request clarification regarding its handling and any subsequent developments,” the email said. She also inquired about the unpublished proposals and lack of follow-up from the board. She sent the email on January 23. She has yet to receive a response, she said.
“It strikes me as a very bizarre process,” she told me. “It’s unacceptable.”
When I spoke to Truitt about the complaint, he told me he did not mean to suggest that Dooley and the other scientists’ perspective was invalid. On the contrary, Truitt was concerned that there weren’t more experts in the working group, or at least more of the right experts. In 2024, the Intergovernmental Panel on Climate Change had hosted a three-day meeting in Italy specifically about the issues with forest carbon accounting, albeit at the national level. Truitt read the final report that came out of that meeting and didn’t understand why none of the scientists involved were on the Protocol’s technical working group.
Initially he wanted to share this concern with the working group directly, he said, but third-party consultants hired to facilitate the group’s progress advised him to bring it to the Protocol’s staff. He did that, and again asked to share it with his colleagues so that it would at least be in the group’s records, but was instructed not to, he said.
Truitt told me his complaint urged the Protocol to invite some of the experts from the IPCC meeting to join the working group. He said that the head of the Independent Standards Board later told him there was not enough time, but that the board would consult with some of those experts once it had the proposals.
The GHG Protocol did not answer detailed questions I sent them for this story. “We are in the process of addressing, through an independent review, a few concerns relating to work within one of our Technical Working Groups,” a spokesperson told me in an email. “As this is an internal ongoing matter, we cannot comment further but we are committed to addressing any findings appropriately.”
The spokesperson also emphasized that robust debate was central to the standard-setting process, and that the organization is “committed to ensuring that all discussions are conducted in a respectful, transparent and well-facilitated manner, with clear governance structures in place to support balanced and evidence-based outcomes. We value all inputs and feedback on how to improve our multistakeholder processes.”
While Truitt and Dooley vehemently disagree on forest carbon accounting and what went wrong in the working group, they are on the same page about one thing — the Protocol has issues with transparency. A new paper published Wednesday argues that the issues Dooley described are systemic, and warns that the Protocol seems to be moving further away from its commitment to accountability.
The paper’s author is Danny Cullenward, an economist and lawyer focused on the scientific integrity of climate policy, who is currently a senior fellow at the University of Pennsylvania’s Kleinman Center for Energy Policy. Cullenward also sits on the Protocol’s Independent Standards Board and is restricted by a non-disclosure agreement from describing what he has witnessed in the role. His paper draws on publicly available information in an effort not to violate his NDA. (Cullenward has also contributed to Heatmap.)
Part of what drove Cullenward to write the piece were concerns outlined in a complaint he and another board member filed jointly to the Protocol. While Cullenward could not discuss the substance of the complaint, his paper notes that it alleges “violations of the Board’s terms of reference,” and that the violations “undermined the scientific integrity of the Board’s deliberations” over the land sector standard.
“I do not have any confidence that we are going to end up in a place where there is public disclosure about what occurred,” he told me, “and that is concerning.”
His paper critiques the Protocol’s formal complaints process more generally, noting that it does not describe how complaints should be adjudicated. Because the Independent Standards Board is bound by an NDA, filing a complaint is the only means by which members can flag malfeasance. If these complaints are then adjudicated in private, there is no “external mechanism to ensure that the Protocol’s overall governance rules are being followed in practice,” Cullenward writes.
He further highlights two overarching failings at the Protocol. The first is that the group’s two key decisionmaking bodies — the Independent Standards Board and the Steering Committee — are imbalanced. The former has members from industry, academia, and government, but no one from environmental non-governmental organizations. More than half the members on the latter are from the business and financial world, and the Steering Committee does not have a single member from the research community.
Not only does the nonprofit community not have a voice on the board, Cullenward writes, but the absence of those voices “risks politicizing the work of scientist Board members.” While the Protocol’s official decision-making hierarchy deems scientific integrity as its top priority, in practice, scientists are left to defend the science to the business community. If and when contentious scientific issues do arise and the board’s decisions are elevated to the Steering Committee, there is no one on that committee with the training to evaluate the disagreement.
Cullenward also criticizes the Protocol for not publishing records from the Independent Standards Board’s meetings, despite the fact that the board’s governance documents explicitly require the publication of meeting minutes. The board’s votes are done by secret ballot, the report says, so members themselves cannot even see how each other voted. Cullenward calls for this rule to be lifted, for votes to be public, and for board members not to be restricted by NDAs. “A well-functioning organization that follows its own rules does not need to restrict Board members’ legal ability to speak about their experiences,” he writes.
Lastly, Cullenward warns that the Protocol seems to be heading down a path of increasing opacity. Last fall, the group announced that it was planning to harmonize its standards with the International Organization for Standardization, or ISO, a separate, much larger group that writes voluntary standards for all kinds of industries. (To date it has written more than 26,000 standards, applying to everything from screw threads and paper sizes to food safety and electrical grids.) The GHG Protocol published new rules governing this joint work, which, unlike the technical working group rules, do not require members’ names be public or a balanced representation of stakeholders.
One of these joint working groups has already been convened, and while the GHG Protocol published the names of the members it nominated to the group on its website, the ISO-nominated members are not listed, and the total group size is unclear. It’s also unclear what this harmonization process will look like, and whether it will involve another overhaul of all of the standards the Protocol has spent the past several years revising.
I reached out to a few other carbon accounting experts for their thoughts on Cullenward’s paper. Michael Gillenwater, the executive director of the Greenhouse Gas Institute, who is in one of the other technical working groups, told me the concerns raised about bias go back to the origins of corporate climate accounting. The focus has long been on “what companies want to report and claim versus what is technically fit for the evolving range of purposes that the GHG Protocol has been and is newly being used for,” he said.
Matthew Brander, a professor of carbon accounting at the University of Edinburgh who also serves on a technical working group, told me he agrees that commercial interests are overrepresented among the working groups — not just in terms of numbers, but also in the amount of time and resources they can spend to engage and lobby for their preferred outcomes. Despite the Protocol’s claim of being “science-led,” he told me, scientific research is often ignored. Brander was also frustrated with the complaints procedure, telling me that a complaint he submitted did not get a substantive response.
“I don’t think there is ever a perfect way of managing/governing standard-setting processes,” he said in an email, “and commercial interests will very often hold sway.”
While Cullenward told me he thought improving transparency and representation would help alleviate many of his concerns, Dooley was less sure.
“The idea that science speaks as an independent, authoritative voice is a myth,” she said. “It’s actually what my research is about. Lots of science is politicized and can be used to support any side of the debate generally. But the way the process was set up very much leant into that and allowed that to happen, rather than mitigated against that.”
Editor’s note: This story has been updated to correct the description of American Forest Foundation and clarify the sharing of papers within the working group.
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Generate Capital, CalSTRS, and the Rhodium Group have teamed up on a new Transition Acceleration Framework to measure and assess emissions impacts.
The most common way to judge whether a company or project is helping to tackle climate change is to measure emissions. Has the company reduced its carbon footprint? Will the project add fewer greenhouse gas emissions to the atmosphere than alternatives?
It’s a useful metric, but a limited one. One company might be doing more to advance the energy transition than another — by investing in an expensive, early-stage solution such as geothermal power, for example — but a comparison of their carbon footprints won’t necessarily show it. At the project level, a solar farm in Mississippi, where solar deployment has lagged, will do more to decarbonize the U.S. power grid than one of equal size in California, even though both projects emit zero carbon.
This presents a challenge for climate-minded investors like Jonah Goldman, the chief strategy officer of Generate Capital, who are trying to figure out where their dollars can make the biggest difference. To solve it, Goldman worked with colleagues at the California State Teachers Retirement System, which backs Generate’s investments, and a team at the Rhodium Group to develop a new way for investors to assess where to put their money.
“The question that most of the frameworks out there ask is, what are your carbon emissions today, and can your carbon emissions be lowered?” Goldman told me. “The Transition Acceleration Framework asks, how can you apply capital that has the best chance of getting to decarbonization over a reasonable time frame?
“It sounds like a similar question. It sounds like semantics. But it’s actually quite different,” he said.
At a high level, the Transition Acceleration Framework measures how much additional decarbonization a given investment can deliver beyond what would likely have occurred anyway. It can also be used to evaluate policy interventions and procurement decisions, such as where to get power for a data center. The Rhodium Group published a white paper describing the methodology on Thursday, as well as an accompanying report using it to evaluate options for powering data centers in the U.S.
The Transition Acceleration Framework has three components: transition potential, transition efficiency, and acceleration factor.
Transition potential is “the size of the emissions-reduction opportunity,” the white paper says — it measures the gap between the current trajectory for a given technology and its potential deployment in a deeply decarbonized world. Some of the solutions with the highest transition potential scores, per Rhodium’s analysis, include light duty electric vehicles and utility-scale solar.
Transition efficiency measures how effective a dollar spent on that technology can be at closing the gap, based on an estimate of the total capital expenditure required to realize the potential. There, more nascent solutions like low-carbon cement and geothermal power score higher than EVs and solar.
Rhodium combines these two complementary metrics into a single “technology factor,” a score on a scale from one to ten that can help identify the highest-leverage sectors to invest in. (The project is similar in spirit to Heatmap’s Decarbonize Your Life series, in which we tried to determine the highest-leverage actions a given individual could take to cut emissions. If you missed it, check it out.)
While the transition potential and efficiency metrics provide a high-level view into how transformative different types of investments can be, the third component of the framework — the acceleration factor — helps distinguish between specific projects.
This starts with an assessment of five “acceleration attributes” — cost reduction, capital availability, new markets, infrastructure and supply chains, and political economy — that represent different mechanisms by which a single investment can help move an entire technology category forward.
For cost reduction, for example, an investor might ask how likely it is that the project will reduce the cost of future deployments through learning by doing or economies of scale. If it’s a first-of-a-kind project, the answer is likely yes. For capital availability, they might look at whether the investment will de-risk the technology. Goldman praised Amazon’s early investment in Rivian delivery vans — not just because it took gas-powered Amazon vans off the road, but because it also spurred other automakers and major shippers such as Walmart and GM to follow suit.
“While the Amazon-Rivian deal wasn’t 100% responsible for it, it certainly was a huge signal to the market that there was safety in solving this last mile delivery problem,” he said.
The Rhodium report outlines a method investors can use to score and weight the various attributes and combine them with the technology factor score to reach a final “acceleration factor” score.
In an accompanying report, Rhodium researchers used the framework to compare a number of different options for powering data centers in the U.S. It’s a high-level assessment — i.e. it doesn’t consider project-specific acceleration attributes — but it provides a rough hierarchy of the arrangements that accelerate the energy transition the most against those that do the most harm. At the top of the list is a grid-connected data center that signs a power purchase agreement with a clean, firm generator, such as a nuclear or geothermal plant. At the bottom, with a negative score indicating it would actually hinder progress relative to a regular grid connection, is an off-grid data center powered entirely by natural gas.
Of course, hyperscalers prioritizing speed to power are unlikely to wait around for a nuclear plant to get built. But there are plenty of options between that and behind the meter gas. An off-grid data center that builds enough renewables and batteries for 95% of its electricity needs and relies on gas backup scores higher than a grid-connected project that buys spot market renewable energy certificates.
“Different data center power configurations can have a meaningfully different impact on the transition, even if you’re looking at things that might on the surface seem relatively similar,” Michael Delgado, a partner at Rhodium, told me.
For now, the Transition Acceleration Framework is just that — a framework. Rhodium is piloting it with Generate and CalSTRS, as well as some additional partners, conducting bespoke assessments or their portfolios and projects. The hope is that it could eventually inform not just individual investment decisions or portfolio analyses but regulations and policy packages.
“This is an open method that we’re trying to put out there and get feedback on from the investment and philanthropic and policy world,” Delgado said.
The question is whether he still has a choice.
The United States has resumed bombing Iran, the U.S. military’s regional command announced on Wednesday. The United States also bombed more than 80 sites on Tuesday, including radar and air defense facilities, but the new set of targets is more expansive.
President Trump declared on Wednesday that the ceasefire between the two countries is dead. Yet he also suggested that an extended war isn’t on the table. “We’re not looking for long term,” he said at the NATO Summit in Turkey. “Anything that happens is going to be over very quickly … and will only make it safer, including for oil.”
Such a statement surely reflects the president’s awareness that his war isn’t very popular among Americans. But does he have any leverage anymore over how long the war lasts? When Trump okayed the interim Iran ceasefire in June, he said that Iran would not toll oil and gas tankers passing through the Strait of Hormuz. Since then, Iran and Oman have started setting up the infrastructure to do just that. That discrepancy may have been the ceasefire’s doom: The truce broke down after Iran fired missiles at oil and natural gas tankers that were allegedly not using its approved route through the strait. (Iran has said that its preferred route through the waterway is the “only safe passage.”)
American officials have said that restoring freedom of navigation through the Strait of Hormuz is one of their goals in ending — and now, resuming — the war. But the strait was open to all before the war began; Iran only shuttered it after the United States and Israel began bombing in February. Yet now that Iran has learned how easily it can close the strait and keep it closed, it has a new weapon to wield over the American and European economies.
And what of the country’s nuclear program? Back in March, it allegedly didn’t play into the calculus, partly because President Trump claimed the U.S. had destroyed the program in 2025. Instead, Secretary of State Marco Rubio said that the president had no choice but to enter the new conflict because Israel was already going to bomb Iran, and since the Islamic Republic would respond by targeting American bases in the Middle East, the United States might as well strike first. A day later, President Trump changed the story, saying that Iran was already planning to bomb U.S. military bases, which forced pre-emptive action on America and Israel’s part.
Yet by April 1, the president had justified the war to the American people by citing Iran’s nuclear program more than 20 times. “For years, everyone has said that Iran cannot have nuclear weapons. But in the end, those are just words, if you’re not willing to take action when the time comes,” he said. The new conflict had obliterated the country’s navy, defense industrial base, and ability to produce missiles, he said. Yet Iran — partly thanks to its small, cheap drones — was able to keep the strait closed for another two months.
What does all of this mean for energy and decarbonization? More expensive fossil fuels. The global crude benchmark Brent surged to $80 a barrel today, while West Texas Intermediate surpassed $74, bringing both to roughly the same level as when the June ceasefire was first announced. Researchers at Brown University estimate that Americans have paid $60 billion — or roughly $500 per household — more for gasoline and diesel than they would have had the conflict never happened.
If this stage of the war doesn’t go “long term,” as Trump hopes, then at least the world will have a little more oil than anticipated to work with, as stockpiles have risen in recent days. But a new and extended phase of the war threatens a return to the prices seen earlier in the spring — or prices that go even higher, should China decline to tap its reserves this time. One potential early pain point is diesel, which is already expensive because of Ukraine’s strikes on Russian refineries. Costlier fuel will keep encouraging more EV sales in Europe, Asia, and even the United States; high diesel prices in particular will provide a tailwind to the shockingly rapid electrification of China’s trucking sector.
Of course, the war will bring much more besides — more squandered time, more military spending, more human misery. It is the first that Trump might regret most. A conflict the White House joined without much public debate — and once forecast would last “four to six weeks” — now looks likely to eat much of his second term.
Pollution from peaker plants combined with heat and smoke can push summer air quality into the danger zone.
If you ever have to pick a day to stay inside, pick July 5. In cities across the United States, the Fourth of July’s pyrotechnic revelries make the wee hours after Independence Day consistently one of the worst of the year for air quality. Just look at Washington, D.C., which briefly held the distinction of having the world’s most polluted air this past Sunday morning following one of the largest firework displays in history.
But if you have to pick a second day to stay inside, shoot for one during the second half of July, which is the hottest period of the year in the United States. For one thing, it’s just plain miserable out. For another, the country’s 1,000 or so peaking power plants, or “peakers,” are more likely to be operating to meet the energy demands of heavy air-conditioning use, emitting disproportionately high levels of pollution for the electricity they generate.
Peakers are the backup power sources operators run only when demand is at its highest, such as during a heat wave. Peakers are also “probably the dirtiest and most expensive energy on the grid,” Abbe Ramanan, who leads the Phase Out Peakers project at the nonprofit Clean Energy Group, told me. “They tend to burn dirtier fuels, such as oil, and typically have older and less efficient emissions control systems.”
Some 63 million Americans live within a three-mile radius of a peaker, according to a 2023 Clean Energy Group report, where they face health conditions including “significant … increases in estimated rates of hospitalization for asthma, acute respiratory infection, and chronic obstructive pulmonary disease,” all conditions associated with proximity to fossil fuel-fired plants. On top of that, historic redlining practices mean two-thirds of peakers are located in communities with a higher percentage of low-income households than the national average, according to the group’s reporting. And yet peakers also provide life-saving power and AC when a blackout could mean death, such as during last week’s heat wave on the East Coast, making them simultaneously a menace and necessity to maintaining public health, at least with our current grid.
What exactly is peaker plant pollution? How does it appear in the Air Quality Index you might see on your phone? And how do local regulators consider pollution when issuing air quality forecasts? I set out to get answers.
To understand peaker plant pollution, let’s start with a refresher on how air quality alerts work.
The AQI scale runs from 0 to 500 and reflects the local concentrations of five major pollutants: particulate matter, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. Each pollutant has an Environmental Protection Agency-regulated benchmark for what is safe (many of which are set at levels clean air advocates argue are too lax). As concentrations increase, the overall AQI rises to warn first “sensitive groups” and then the general public when to take precautions, such as limiting outdoor activity or wearing a mask. (To learn more about the AQI scale, read my colleague Emily Pontecorvo’s explainer here.)
As do all fossil fuel power plants, peakers release planet-warming carbon dioxide as a byproduct of combustion, along with nitrogen oxides, particulate matter, volatile organic compounds, and other trace toxins that aren’t captured in the AQI, such as heavy metals. Oil and coal-fired power plants also release sulfur dioxide, which creates acid rain; natural gas-fired plants, on the other hand, emit comparatively little.
While NOx is an irritant in its own right, it is, more significantly, a key ingredient in the chemical reaction that creates ozone. When NOx mixes with volatile organic compounds — found in vehicle exhaust, personal care products, and yes, also power plant emissions — on a warm, sunny day, the chemical reaction creates ground-level ozone, which is corrosive enough to scar lung tissue with repeated, prolonged exposure. An expert once helpfully likened it to me as “sunburn on your lungs.” Health researchers have determined that, globally, ozone (also known as smog) causes a million premature deaths every year.
Yes, although it’s not an easy or neat measurement.
Peaker plants are used to rapidly supply electricity to the grid when demand exceeds the baseload capacity. As a result, they run infrequently — only about 5% of the year, or 464 hours per plant, in 2022, per Clean Energy Group’s analysis of 2022 EPA data. Using a stricter definition of peakers, the Government Accountability Office found that the plants represent nearly a fifth of the nation’s potential generating capacity but produce only about a 30th of its overall electricity, mostly due to the time they spend sitting idle.
Power plants use a number of emission control systems to limit emissions of various pollutants. But the EPA has much looser requirements for low-operating peakers, which “may not have effective, if any, emissions control technology,” the GAO writes. When operational, peakers emit an estimated 60 million tons of CO2 per year, with a median NOx emission rate about 6.1 times greater per unit of electricity generated by natural gas-fueled peakers compared to non-peaker gas plants.
“One really big issue with peakers is the emissions control systems are not operating during times when the plant is starting up or shutting down, which means that emissions are just unabated during those times,” Ramanan told me. “And because those plants tend to operate in short bursts, such as during a heat wave, they will start up and shut down more frequently.” Even up to a day beforehand, when the plant is running its test cycle, it might be emitting pollutants even while not actually providing any power.
One 2017 study by University of Wisconsin–Madison researchers found that across the Eastern U.S. from 2007 to 2012, total electricity generation rose by about 4% for every 1-degree Celsius (1.8-degree Fahrenheit) increase in daily summer temperature, with NOx correspondingly up 3.6% and CO2 up 3.3%. Though these numbers aren’t peaker-specific, the plants represent a disproportionate share of the rise since they’re reserved for the hottest, heaviest-load days.
Though the slower rise in NOx suggests “slightly cleaner plants … on average,” the authors write, that is “not completely unexpected, as new natural gas plants are required to have controls installed even as some peaking plants do not.” They note, however, that their data does not fully capture grandfathered-in units, since gas- and oil-fired peakers are allowed non-direct-measurement reporting.
In fact, in Maine and Connecticut, which “use more petroleum for electricity generation than most states in the U.S., primarily as peaking plants deployed on the hottest days,” NOx jumped 33% and 23% per degree Celsius, respectively. Separately, a 2016 study found that peaking plants may have accounted for up to 87% of local particulate matter in the PJM Interconnection during a July 2006 heat wave.
Peaker plant pollution is significant enough that chronic exposure in local communities has measurable health impacts. But how does it factor into summer AQI levels?
My colleague Matthew Zeitlin spoke this week with Margaret LaFarr, the New York State Department of Environmental Conservation’s director of air resources, who told him that peaker plant pollution is “one of the factors we consider” in formulating its air quality forecasts. But because the state’s agency uses modeling to predict when and where air quality will be poor, the granularity of a single peaker just isn’t there. “If we have to have specific information on the emissions, it would not be ready in time for a timely advisory,” LaFarr said.
Ramanan, whose nonprofit has diligently recorded the negative impacts of peakers, concurred that it is “difficult to pinpoint just how much peaker plants contribute to local air pollution because those sorts of studies are just very expensive to do.” Studies that look at disproportionate health impacts, on the other hand, are a little simpler to put together.
Additionally, while the AQI might rise locally near peakers during a heat wave, because of the nature of the scale, it can’t neatly distinguish why. A high ozone reading, for example, might just as easily be due to tailpipe emissions on a hot day; in the New York metro area, vehicles are responsible for an estimated 60% of the air pollution. Meteorological conditions — whether it’s sunny, a key factor in ozone formation, or which way the wind is blowing — obscure the picture. Particulate matter readings could be from a peaker, for example, but they could just as easily be from wildfire smoke.
One way air quality activists like to think about peaker pollution is as a co-occurrence — that is, a compounding pollution on top of already degraded conditions. Hot days tend to be the worst for ozone already, because of the aforementioned tailpipe pollution; peakers, activated to help with the heat-related energy load, then release more ozone-generating emissions at the worst possible time.
While a precise breakdown of the AQI might not be there for peakers, “we know the days that are more conducive to ozone formation generally tend to be those same days where people are cranking up their ACs and there is a higher demand for energy,” LaFarr said.
There is some speculation that cleaner input fuels could help reduce the worst peaker plant emissions. Generally, this is true: The 2017 study by the University of Wisconsin–Madison researchers found that from 1997 to 2015, in Texas, petroleum use in electricity generation dropped 85% and coal dropped 12%, while natural gas increased 57%. As a result, Texas had the lowest level of SO2 sensitivity of any state.
But beyond the existing fuel mixes, fuel switching is not a clean fix for peaker plants. “Burning things like hydrogen and [methane captured from waste processing facilities] don’t actually reduce the air pollution burden in any meaningful way,” Ramanan argued. “Hydrogen in particular tends to actually have extremely high levels of NOx emissions when it’s combusted.”
In Astoria, a neighborhood of New York City, activists opposed retrofitting the local oil-powered peaker plant to run on natural gas because doing so would “lock the state into relying on fossil fuels for decades, fly in the face of the state’s climate law that requires a drastic reduction in carbon emissions by mid-century and continue to pollute in an already overburdened community where many residents are immigrants and live below the poverty line,” Inside Climate News reported. At the same time, doing so would “reduce the state’s greenhouse gas emissions by more than 5 million tons through the year 2035,” per its owner, NRG Energy.
But a third way emerged: New York eventually denied NRG’s permit because it violated the state’s climate law, and the utility subsequently sold the Astoria facility to serve as the converter station for Beacon Wind, a development off the coasts of New York and Massachusetts.
While wind, new transmission, and battery storage all face enormous headwinds in the current political climate — meaning that many peaker plants targeted by activists for retirement are likely to stick around for years yet — advocates remain adamant that a playbook exists for decarbonization. “In terms of replacing one-to-one capacity, we’ve been looking at battery storage even just at peaker plant sites that can be paired with renewables or grid connected batteries,” Ramanan said, adding that “really great work is also being done in terms of virtual power plants and demand reduction — because it’s not just about reducing peak capacity, it’s also reducing the peak overall.”
That raises a final, particularly thorny question: Is air pollution from peaker plants “worth it” if it means being able to run AC?
A 2018 follow-up study by the same team of researchers at the University of Wisconsin–Madison explored a similar question. They found that climate change alone would increase summer mortality related to the smallest airborne particulate pollution by more than 13,500 deaths, and ozone-related mortality by more than 3,500 deaths in a mid-century scenario. AC-driven power sector emissions — full-fleet numbers, albeit disproportionately including peakers — would, on top of that, account for 654 PM 2.5 deaths and 315 ozone deaths, a nearly 5% and 9% increase, respectively, over climate impacts alone.
Researchers credit access to air conditioning in the United States with a 75% decline in deaths, and modeling exercises frequently show that a blackout during a heat wave could realistically result in hundreds of thousands of people needing medical attention. But clean air advocates also point to examples like Astoria, where the denial of a permit to retrofit a peaker plant for slightly better fossil fuels resulted in the grounds being used for a renewable energy source instead.
It’s certainly not an easily replicable process given the current political and economic climate, but it also perhaps suggests a false dichotomy of peakers vs. AC. Affordable power and livable spaces are just two among a host of community needs energy and public health officials must keep in mind.
“It’s not enough to just replace the existing system with renewables and battery storage and have fewer emissions,” Ramanan said. “It also has to be equitable, because otherwise we’re just going to replicate the same issues we’re having now in different ways.”