Category Archives: Climate Change

Democrats are seriously tackling the climate crisis: No more half-measures or neoliberal compromises

At least seven 2020 candidates have serious climate plans — and they’re not bowing to fossil-fuel interests

By Carl Pope, June 16, 2019 10:00AM (UTC)
Jay Inslee; Beto O’Rourke; Joe Biden; Bernie Sanders (AP/Getty/Salon) / Elizabeth Warren; John Hickenlooper; John Delaney

Already seven Democratic presidential hopefuls have offered detailed plans for confronting the climate crisis — including the two current (perceived) frontrunners, “moderate” Joe Biden and “progressive” Bernie Sanders, along with Elizabeth Warren, Beto O’Rourke, Jay Inslee, John Hickenlooper and John Delaney. (Kamala Harris, Cory Booker and Kirsten Gillibrand have sponsored the Green New Deal resolution but have not yet released individual policies.)

Media coverage has predictably focused on the horse race: What significance the increased salience of the issue has with primary voters, how the plans and candidates differ from each other, and whether there will or will not be a separate debate on climate. (At this writing, the Democratic National Committee still says there won’t be.)

But from a climate perspective, what’s revealing (and fascinating) is the degree to which the candidates and their plans are, at heart, indistinguishable. As a group, none of these climate planks harken back to Barack Obama’s “all of the above” genuflection to the enduring political power of fossil fuels. Nor do they resemble Hillary Clinton’s 2016 proposals, which focused almost entirely on renewable power — ambitious but narrow. They eschew the carbon-pricing emphasis of many Beltway economists and policy mavens. And they avoid the austerity frame that climate deniers have for so long used to dampen public support for clean energy.

Taken as a group, this year’s presidential climate proffers are far broader — and more economically and politically sophisticated — than four years ago. If they have a 2016 antecedent, it is Bernie Sanders’ approach, which culminated in Sanders’ successful effort to buttress the Democratic platform on climate by including ambitious greenhouse emission targets.

But the Democratic candidates have also introduced some new ingredients, drawn heavily from the Green New Deal. Here’s what the emerging Democratic climate platform looks like, and why it’s important.

1. Climate science and ambitious decarbonization goals are in.

While avoiding the confusing Green New Deal language about decarbonizing the economy within a decade, almost all of the candidates commit to get the job done by mid-century. Inslee pledges net zero emissions by 2045, Biden and O’Rourke by 2050. Sanders and Warren offer no date, although Sanders in 2016 called for a 40% emission reduction by 2030.

Fundamentally, all these Democrats are saying that we can and should, decarbonize our economy fully by mid-century, and the differences in their formal pledges are almost irrelevant this far in advance.

2. Climate sacrifice and austerity are out.

None of the candidates suggest that to accomplish this goal Americans need to sacrifice prosperity or freedom — instead they all call for tying a transition to clean energy to a major revitalization of the U.S. economy, with several specifically calling out manufacturing. So striking is this pattern that the New York Times complained about it.

3. Investment, not carbon pricing, is the new silver bullet.

Carbon taxes or “cap and trade” aren’t central to the candidates’ thinking. Delaney and perhaps Hickenlooper aside, those with detailed plans all implicitly turn to a mixture of carrots — R&D, investments, incentives — and sticks, meaning regulations and only perhaps some carbon pricing, to do the job. Inslee, having campaigned unsuccessfully for a carbon tax as governor of Washington, doesn’t repeat his call for one. Biden and O’Rourke call for some kind of mandatory mechanism, but don’t specify pricing. Warren and Sanders don’t mention it. Indeed, none of the leading candidates except Pete Buttigieg explicitly favors such a tax.

The Green New Deal is the source of the single newest ingredient in the policies as a group — the emphasis on massive federal investment in place of carbon pricing. Again, the nominal size of investment varies. O’Rourke asks for $5 trillion, Warren $3 trillion and Biden $1.7 trillion. These numbers represent different program mixes and financial strategies. All a voter can truly discern from them is “I want the government to invest more in American climate progress and I think the number should be big, because the economic gains will be much bigger.” That’s a far cry from the language historically used to advocate carbon pricing.

4. Standards and regulation are back.

The idea of using emission standards as if climate were a pollution problem seems to have caught on. To begin with, all the Democratic presidential candidates support restoring Obama-era emission standards which Trump has rolled back or is trying to. Biden, Inslee, Sanders, O’Rourke and Warren explicitly call for additional regulations to get to zero emissions by 2050.

Inslee and O’Rourke explicitly flag powerful regulatory mandates to decarbonize buildings, utilities and transportation; Biden focuses on transportation; O’Rourke on buildings; Sanders and Warren don’t address sectors.

5. It’s not just electricity — economy-wide approaches are embraced.

The emphasis on investment and regulations frees the candidates up to push for emissions reductions outside the electricity sectors. With those tolls the U.S. has clear pathways to 100% clean energy in three sectors of our economy: electricity generation, road and rail transportation, and buildings. Clean power is already cheaper almost everywhere than coal and natural gas; operating fleets of electric vehicles is cheaper than continuing to buy new gasoline or diesel models; and all-electric, hyper-efficient new buildings cost less to own and operate than leaky ones reliant on oil or natural gas for heating and cooling.

Allowing time for turnover of power plants, vehicles and furnaces, all three of these sectors can be profitably transitioned to 100% clean electricity — so investing in speeding up the transition here with massive federal investments does, indeed, make marvelous economic sense.

Biden and Inslee give the most detailed road maps, but the other candidates with plans seem headed in the same direction.

Finally, research gets respect

These presidential platforms emphasize the need for expanded clean energy research and development, along with deployment of the technologies we have already commercialized. The three sectors discussed above account for only 70% of our emissions.  pollution from the remaining 30% — industry, agriculture, aviation and shipping — requires new approaches and technologies, and significant federal support for research, development, and early stage deployment. All the Democratic candidates call for such investments, and all offer policies to ensure that along with clean energy comes a revival of American manufacturing.

How do the politics look?

The right wing and the carbon lobby seem to be teeing up their usual attack on climate advocacy: It will tank the economy and deprive Americans of economic freedom! Republican opponents of climate progress don’t seem to have realized that the Democrats, while raising their ambition on climate and clean energy, have walked away from the taxation, sacrifice and austerity traps. The right wing has attacked Biden, their current whipping boy, for offering a climate plan, suggesting that since swing voters don’t show the same level of interest in climate issues that Democrats do, Republicans will be able to play the climate austerity card against Biden — or any other Democratic nominee who dares to offer a real climate plan.

The problem with this theory is that while swing voters may not prioritize climate, they love clean energy and they want more investment  in America — and that’s what Democrats are offering. Most of the Democratic candidates, Warren and Biden in particular, are focused on reviving manufacturing, the (broken) promise that carried the Midwest for Donald Trump in 2016.

And from voices like Greenpeace, candidates are being ranked not only on their demand-side fossil fuel policies, but on where they stand on coal mining and oil and gas drilling and exploration.

The Beltway establishment is complaining about this willingness of the Democratic presidential field to place carbon pricing where it belongs — as one of a series of needed market reforms that enable us to decarbonize, but not as a fetish totem in itself. Catherine Rampel in the Washington Post lamented this feature, calling a price on carbon “the obvious, no-brainer tool for curbing carbon emissions.”  But it appears the candidates have noted the fact that when given a chance to vote on pricing carbon, even Jay Inslee’s green constituents in Washington state twice politely demurred.

In many ways, the Democratic field is following the pathway blazed by California under the governorships of Arnold Schwarzenegger and Jerry Brown. Let the public and the legislature set broad and ambitious climate goals. Then pragmatically deploy administrative rules and incentives to test and perfect pathways toward a clean energy economy. As that economy grows in strength, it will challenge and defeat the stranglehold that fossil fuel interests have held for a century over America’s future, and create the politics for a more ambitious next round of emissions reduction targets.


Carl Pope is the co-author of “Climate of Hope: How Cities, Businesses, and Citizens Can Save the Planet.” He is the former CEO and chairman of the Sierra Club.
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    Trump Administration Hardens Its Attack on Climate Science

    By Coral Davenport & Mark Landler, The New York Times,  May 27, 2019
    The Huntington Canyon coal-fired power plant in Utah. The White House, already pursuing major rollbacks of greenhouse-gas emission restrictions, is amplifying its attack on fundamental climate-science conclusions. Credit: Brandon Thibodeaux for The New York Times

    WASHINGTON — President Trump has rolled back environmental regulations, pulled the United States out of the Paris climate accord, brushed aside dire predictions about the effects of climate change, and turned the term “global warming” into a punch line rather than a prognosis.

    Now, after two years spent unraveling the policies of his predecessors, Mr. Trump and his political appointees are launching a new assault.

    In the next few months, the White House will complete the rollback of the most significant federal effort to curb greenhouse-gas emissions, initiated during the Obama administration. It will expand its efforts to impose Mr. Trump’s hard-line views on other nations, building on his retreat from the Paris accord and his recent refusal to sign a communiqué to protect the rapidly melting Arctic region unless it was stripped of any references to climate change.

    And, in what could be Mr. Trump’s most consequential action yet, his administration will seek to undermine the very science on which climate change policy rests.

    Mr. Trump is less an ideologue than an armchair naysayer about climate change, according to people who know him. He came into office viewing agencies like the Environmental Protection Agency as bastions of what he calls the “deep state,” and his contempt for their past work on the issue is an animating factor in trying to force them to abandon key aspects of the methodology they use to try to understand the causes and consequences of a dangerously warming planet.

    As a result, parts of the federal government will no longer fulfill what scientists say is one of the most urgent jobs of climate science studies: reporting on the future effects of a rapidly warming planet and presenting a picture of what the earth could look like by the end of the century if the global economy continues to emit heat-trapping carbon dioxide pollution from burning fossil fuels.

    The attack on science is underway throughout the government. In the most recent example, the White House-appointed director of the United States Geological Survey, James Reilly, a former astronaut and petroleum geologist, has ordered that scientific assessments produced by that office use only computer-generated climate models that project the impact of climate change through 2040, rather than through the end of the century, as had been done previously.

    President Trump has pushed to resurrect the idea of holding public debates on the validity of climate science. Credit: Doug Mills/The New York Times

    Scientists say that would give a misleading picture because the biggest effects of current emissions will be felt after 2040. Models show that the planet will most likely warm at about the same rate through about 2050. From that point until the end of the century, however, the rate of warming differs significantly with an increase or decrease in carbon emissions.

    The administration’s prime target has been the National Climate Assessment, produced by an interagency task force roughly every four years since 2000. Government scientists used computer-generated models in their most recent report to project that if fossil fuel emissions continue unchecked, the earth’s atmosphere could warm by as much as eight degrees Fahrenheit by the end of the century. That would lead to drastically higher sea levels, more devastating storms and droughts, crop failures, food losses and severe health consequences.

    Work on the next report, which is expected to be released in 2021 or 2022, has already begun. But from now on, officials said, such worst-case scenario projections will not automatically be included in the National Climate Assessment or in some other scientific reports produced by the government.

    “What we have here is a pretty blatant attempt to politicize the science — to push the science in a direction that’s consistent with their politics,” said Philip B. Duffy, the president of the Woods Hole Research Center, who served on a National Academy of Sciences panel that reviewed the government’s most recent National Climate Assessment. “It reminds me of the Soviet Union.”

    In an email, James Hewitt, a spokesman for the Environmental Protection Agency, defended the proposed changes.

    “The previous use of inaccurate modeling that focuses on worst-case emissions scenarios, that does not reflect real-world conditions, needs to be thoroughly re-examined and tested if such information is going to serve as the scientific foundation of nationwide decision-making now and in the future,” Mr. Hewitt said.

    However, the goal of political appointees in the Trump administration is not just to change the climate assessment’s methodology, which has broad scientific consensus, but also to question its conclusions by creating a new climate review panel. That effort is led by a 79-year-old physicist who had a respected career at Princeton but has become better known in recent years for attacking the science of man-made climate change and for defending the virtues of carbon dioxide — sometimes to an awkward degree.

    The Beaufort Sea in the Arctic, a region that is warming rapidly. The United States recently declined to sign a communiqué on protecting the Arctic unless it omitted references to climate change. Credit: Andrew Testa for The New York Times

    “The demonization of carbon dioxide is just like the demonization of the poor Jews under Hitler,” the physicist, William Happer, who serves on the National Security Council as the president’s deputy assistant for emerging technologies, said in 2014 in an interview with CNBC.

    Mr. Happer’s proposed panel is backed by John R. Bolton, the president’s national security adviser, who brought Mr. Happer into the N.S.C. after an earlier effort to recruit him during the transition.

    Mr. Happer and Mr. Bolton are both beneficiaries of Robert and Rebekah Mercer, the far-right billionaire and his daughter who have funded efforts to debunk climate science. The Mercers gave money to a super PAC affiliated with Mr. Bolton before he entered government and to an advocacy group headed by Mr. Happer.

    Climate scientists are dismissive of Mr. Happer; his former colleagues at Princeton are chagrined. And several White House officials — including Larry Kudlow, the president’s chief economic adviser — have urged Mr. Trump not to adopt Mr. Happer’s proposal, on the grounds that it would be perceived as a White House attack on science.

    Even Stephen K. Bannon, the former White House strategist who views Mr. Happer as “the climate hustler’s worst nightmare — a world-class physicist from the nation’s leading institution of advanced learning, who does not suffer fools gladly,” is apprehensive about what Mr. Happer is trying to do.

    “The very idea will start a holy war on cable before 2020,” he said. “Better to win now and introduce the study in the second inaugural address.”

    But at a White House meeting on May 1, at which the skeptical advisers made their case, Mr. Trump appeared unpersuaded, people familiar with the meeting said. Mr. Happer, they said, is optimistic that the panel will go forward.

    William Happer, who serves on the National Security Council, is pushing to create a climate review panel that would question scientific consensus. Credit: Pool photo by Albin Lohr-Jones

    The concept is not new. Mr. Trump has pushed to resurrect the idea of a series of military-style exercises, known as “red team, blue team” debates, on the validity of climate science first promoted by Scott Pruitt, the E.P.A. administrator who was forced to resign last year amid multiple scandals.

    At the time, the idea was shot down by John F. Kelly, then the White House chief of staff. But since Mr. Kelly’s departure, Mr. Trump has talked about using Mr. Happer’s proposed panel as a forum for it.

    For Mr. Trump, climate change is often the subject of mockery. “Wouldn’t be bad to have a little of that good old fashioned Global Warming right now!” he posted on Twitter in January when a snowstorm was freezing much of the country.

    His views are influenced mainly by friends and donors like Carl Icahn, the New York investor who owns oil refineries, and the oil-and-gas billionaire Harold Hamm — both of whom pushed Mr. Trump to deregulate the energy industry.

    Mr. Trump’s daughter Ivanka made a well-publicized effort to talk him out of leaving the Paris accord in 2017. But after being vanquished by officials including Mr. Bannon, Mr. Pruitt, former Attorney General Jeff Sessions and the former White House counsel Donald F. McGahn II, there is little evidence she has resisted his approach since then.

    The president’s advisers amplify his disregard. At the meeting of the eight-nation Arctic Council this month, Secretary of State Mike Pompeo dismayed fellow diplomats by describing the rapidly warming region as a land of “opportunity and abundance” because of its untapped reserves of oil, gas, uranium, gold, fish and rare-earth minerals. The melting sea ice, he said, was opening up new shipping routes.

    “That is one of the most crude messages one could deliver,” said R. Nicholas Burns, who served as the NATO ambassador under George W. Bush.

    Secretary of State Mike Pompeo dismayed fellow diplomats by describing the Arctic as a land of “opportunity and abundance” as a consequence of global warming. Credit: Mandel Ngan/Agence France-Presse — Getty Images

    At the National Security Council, under Mr. Bolton, officials said they had been instructed to strip references to global warming from speeches and other formal statements. But such political edicts pale in significance to the changes in the methodology of scientific reports.

    Mr. Reilly, the head of the Geological Survey, who does not have a background in climate change science, characterized the changes as an attempt to prepare more careful, accurate reports. “We’re looking for answers with our partners and to get statistical significance from what we understand,” he said.

    Yet scientists said that by eliminating the projected effects of increased carbon dioxide pollution after 2040, the Geological Survey reports would present an incomplete and falsely optimistic picture of the impact of continuing to burn unlimited amounts of coal, oil and gasoline.

    “The scenarios in these reports that show different outcomes are like going to the doctor, who tells you, ‘If you don’t change your bad eating habits, and you don’t start to exercise, you’ll need a quadruple bypass, but if you do change your lifestyle, you’ll have a different outcome,’” said Katharine Hayhoe, the director of the Climate Science Center at Texas Tech University and an author of the National Climate Assessment.

    Not all government science agencies are planning such changes. A spokesman for the National Oceanic and Atmospheric Administration, asked if its scientists would limit the use of climate models, wrote in an email, “No changes are being considered at this time.”

    The push to alter the results of at least some climate science reports, several officials said, came after November’s release of the second volume of the National Climate Assessment.

    While the Trump administration did not try to rewrite the scientific conclusions of the report, officials sought to play it down — releasing it the day after Thanksgiving — and discredit it, with a White House statement calling it “largely based on the most extreme scenario.”

    This summer, the E.P.A. is expected to finalize the legal rollback of two of President Barack Obama’s most consequential policies: regulations to curb planet-warming pollution from vehicles and power plants. Credit: George Etheredge for The New York Times

    Still, the report could create legal problems for Mr. Trump’s agenda of abolishing regulations. This summer, the E.P.A. is expected to finalize the legal rollback of two of President Barack Obama’s most consequential policies: federal regulations to curb planet-warming pollution from vehicle tailpipes and power plant smokestacks.

    Opponents say that when they challenge the moves in court, they intend to point to the climate assessment, asking how the government can justify the reversals when its own agencies have concluded that the pollution will be so harmful.

    That is why officials are now discussing how to influence the conclusions of the next National Climate Assessment.

    “They’ve started talking about how they can produce a report that doesn’t lead to some silly alarmist predictions about the future,” said Myron Ebell, who heads the energy program at the Competitive Enterprise Institute, an industry-funded research organization, and who led the administration’s transition at the E.P.A.

    A key change, he said, would be to emphasize historic temperatures rather than models of future atmospheric temperatures, and to eliminate the “worst-case scenarios” of the effect of increased carbon dioxide pollution — sometimes referred to as “business as usual” scenarios because they imply no efforts to curb emissions.

    Scientists said that eliminating the worst-case scenario would give a falsely optimistic picture. “Nobody in the world does climate science like that,” said Michael Oppenheimer, a professor of geosciences and international affairs at Princeton. “It would be like designing cars without seatbelts or airbags.”

    Outside the United States, climate scientists had long given up on the White House being anything but on outlier in policy. But they worry about the loss of the government as a source for reliable climate research.

    “It is very unfortunate and potentially even quite damaging that the Trump administration behaves this way,” said Johan Rockström, the director of the Potsdam Institute for Climate Impact Research in Germany. “There is this arrogance and disrespect for scientific advancement — this very demoralizing lack of respect for your own experts and agencies.”

    A version of this article appears in print on May 27, 2019, on Page A1 of the New York edition with the headline: In Climate Fight, Trump Will Put Science on Trial.
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      E.P.A. Plans to Get Thousands of Deaths Off the Books by Changing Its Math

      By Lisa Friedman, New York Times, May 20, 2019
      The Hunter power plant in Castle Dale, Utah, which burns an estimated 4.5 million tons of coal a year.  Credit: Brandon Thibodeaux for The New York Times

      WASHINGTON — The Environmental Protection Agency plans to change the way it calculates the future health risks of air pollution, a shift that would predict thousands of fewer deaths and would help justify the planned rollback of a key climate change measure, according to five people with knowledge of the agency’s plans.

      The proposed change would dramatically reduce the 1,400 additional premature deaths per year that the E.P.A. had initially forecast as a result of eliminating the old climate change regulation — the Clean Power Plan, which was President Barack Obama’s signature climate change measure. It would also make it easier for the administration to defend its replacement, known as the Affordable Clean Energy rule.

      It has been a constant struggle for the E.P.A. to demonstrate, as it is normally expected to do, that society will see more benefits than costs from major regulatory changes. The new modeling method, which experts said has never been peer-reviewed and is not scientifically sound, would most likely be used by the Trump administration to defend further rollbacks of air pollution rules.

      It is not uncommon for a presidential administration to use accounting changes to make its regulatory decisions look better than the rules of its predecessors. But the proposed new modeling method is unusual because it relies on unfounded medical assumptions and discards more than a decade of peer-reviewed E.P.A. methods for understanding the health hazards linked to the fine particulate matter produced by burning fossil fuels.

      Fine particulate matter — the tiny, deadly particles that can penetrate deep into the lungs and enter the bloodstream — is linked heart attacks, strokes and respiratory disease.

      The five people familiar with the plan, who are all current or former E.P.A. officials, said the new modeling method would be used in the agency’s analysis of the final version of the ACE rule, which is expected to be made public in June. William L. Wehrum, the E.P.A. air quality chief, acknowledged in an interview the new method would be included in the agency’s final analysis of the rule.

      The new methodology would assume there is little or no health benefit to making the air any cleaner than what the law requires. On paper, that would translate into far fewer premature deaths from air pollution, even if it increased. The problem is, scientists say, in the real world there are no safe levels of fine particulate pollution in the air.

      “Particulate matter is extremely harmful and it leads to a large number of premature deaths,” said Richard L. Revesz, an expert in environmental law at New York University. He called the expected change a “monumental departure” from the approach both Republican and Democratic E.P.A. leaders have used over the past several decades and predicted that it would lay the groundwork for weakening more environmental regulations.

      “It could be an enormously significant impact,” Mr. Revesz said.

      The Obama administration had sought to reduce planet-warming greenhouse gas emissions under the Clean Power Plan by pushing utilities to switch away from coal and instead use natural gas or renewable energy to generate electricity. The Obama plan would also have what’s known as a co-benefit: levels of fine particulate matter would fall.

      The Trump administration has moved to repeal the Obama-era plan and replace it with the ACE rule, which would slightly improve the efficiency of coal plants. It would also allow older coal plants to remain in operation longer and result in an increase of particulate matter.

      Particulate matter comes in various sizes. The greatest health risk comes from what is known as PM 2.5, the range of fine particles that are less than 2.5 microns in diameter. That is about one-thirtieth the width of a human hair.

      The E.P.A. has set the safety threshold for PM 2.5 at a yearly average of 12 micrograms per cubic meter. While individual days vary, with some higher, an annual average at or below that level, known as the particulate matter standard, is considered safe. However, the agency still weighs health hazards that occur in the safe range when it analyzes new regulations.

      Industry has long questioned that system. After all, fossil fuel advocates ask, why should the E.P.A. search for health dangers, and, ultimately, impose costs on industry, in situations where air is officially considered safe?

      Mr. Wehrum, who worked as a lawyer and lobbyist for chemical manufacturers and fossil fuel businesses before moving to the E.P.A., echoed that position in the interview. He noted that, in some regulations, the benefits of reduced particulate matter have been estimated to total in the range of $40 billion.

      “How in the world can you get $30 or $40 billion of benefit to public health when most of that is attributable to reductions in areas that already meet a health-based standard,” he said. “That doesn’t make any sense.”

      William L. Wehrum, the E.P.A. assistant administrator for air and radiation. Credit: Ron Sachs/CNP/MediaPunch

      Mr. Wehrum confirmed that he had asked his staff to study the issue and that the final version of the ACE rule would include a variety of analyses, including one that does not take into consideration health effects below the particulate matter standard. He acknowledged that doing so would reduce the 1,400 premature deaths the agency had initially predicted as a result of the measure.

      He called the attention given to that initial forecast “unfortunate” and said the agency had included the figure in its analysis to show the varied results that can be achieved based on different assumptions.

      Mr. Wehrum said the analyses the agency is conducting “illuminate the issue” of particulate matter and the question of what level is acceptable for the purposes of policymaking. He said new approaches would allow for public debate to move ahead and that any new methods would be subject to peer review if they became the agency’s primary tool for measuring health risks.

      “This isn’t just something I’m cooking up here in my fifth-floor office in Washington,” Mr. Wehrum said.

      Roger O. McClellan, who has served on E.P.A. advisory boards and as president of the Chemical Industry Institute of Toxicology, an industry-financed research center, said the data for health risks below the particulate matter standard was weak and that he did not accept the argument that agencies must calculate risk “down to the first molecule of exposure.”

      “These kinds of approaches — that every molecule, every ionization, carries with it an associated calculable health risk — are just misleading,” Mr. McClellan said.

      To put the matter in perspective, most scientists say particulate matter standards are like speed limits. On many highways, a limit of 65 miles per hour is considered reasonable to protect public safety. But that doesn’t mean the risk of an accident disappears at 55 m.p.h., or even 25.

      Jonathan M. Samet, a pulmonary disease specialist who is dean of the Colorado School of Public Health, said the most recent studies showed negative health effects well below the 12-microgram standard. “It’s not a hard stop where we can say ‘below that, air is safe.’ That would not be supported by the scientific evidence,” Dr. Samet said. “It would be very nice for public health if things worked that way, but they don’t seem to.”

      Daniel S. Greenbaum, president of the Health Effects Institute, a nonprofit research organization that is funded by the E.P.A. and industry groups, acknowledged there was uncertainty around the effects of fine particulate matter exposure below the standard.

      He said it was reasonable of the Trump administration to study the issue, but he questioned moving ahead with a new system before those studies are in. “To move away from the way this has been done without the benefit of this full scientific peer review is unfortunate,” he said.


      For more news on climate and the environment, follow @NYTClimate on Twitter.
      Lisa Friedman reports on climate and environmental policy in Washington. A former editor at Climatewire, she has covered nine international climate talks. @LFFriedman
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