This article was updated and corrected on May 24 to reflect the scope of the advisory group's memoranda, which also call for reviews of regulatory rollbacks on carbon dioxide from power plants and methane from oil and gas operations.

Scott Pruitt, the embattled head of the Environmental Protection Agency, faces a broadening challenge to his efforts to roll back greenhouse gas regulations, as agency science advisers expand the list of policies they want to vet at an upcoming meeting.

A work group of the EPA's Science Advisory Board, in a May 18 memo, has added three more of his actions to a list they want reviewed by the full board: the weakening of auto efficiency and emissions standards, Pruitt's elimination of a rule to curb truck pollution, and the cost-benefit analysis underpinning the Clean Power Plan, which the Trump administration is trying to undo. In an April 30 memo, the work group called for the full board to review Pruitt's repealing of the Clean Power Plan

The main purpose of the board is to review the quality and relevance of scientific research used by the EPA to draft regulations.

The group's actions signal that the full board's May 31-June 1 meeting will be partly devoted to the scientific community's harshest critiques of President Donald Trump's deregulatory agenda.

The same 10-member work group, which includes four of Pruitt's own appointees, already had called for a full board review of his effort to restrict the agency's use of scientific studies.

In the new memo, the agency science advisers—all outside academics and consultants with expertise in the science and technology related to the proposed EPA actions—picked apart the Pruitt proposals.

In every case, they noted that the assertions Pruitt's EPA made to support its regulatory rollbacks lacked peer review or independent evaluation. They also noted the agency's failure to take into account the impact of its actions on future greenhouse gas emissions, public health and safety due to climate change, or the indirect impact due to an increase of other pollutants.

"These would seem to be logical and necessary areas for scientific and technical assessment," the work group said. "Such information must be transparent, accessible to the public, and appropriately peer-reviewed."

As for one of the more arcane actions they challenged—a recalibration of what economists call the "social cost of carbon," a calculation of the future damages of climate change expressed in today's dollars—they warned that he was writing off the costs that global warming would inflict on "future generations which will be most impacted."

Holes in Pruitt's Fuel Efficiency Claims

The work group pointed to holes in Pruitt's evidence for his "final determination" that President Obama's vehicle fuel efficiency plan for the 2022-2025 model years went too far and should be revised.

Pruitt said, for instance, that electric car sales had decreased, an assertion based on a single public comment to the agency. But the work group noted that was based on "incomplete information," not taking into account the increase in electric car sales after 2015, or the shift to plug-in and battery-electric vehicles from hybrids.

Pruitt also said electric car sales would be necessary to meet the Obama standards. But the work group said a number of the peer-reviewed studies "do not support this assumption." The National Research Council, they noted, has shown how the standards could be met with downsized turbocharged engines and other technologies to reduce gasoline consumption.

The work group members also questioned Pruitt's purported concern about fuel economy standards' impact on the poor.

"EPA expressed concern about the affordability of new vehicles to low income households, but did not express concern regarding the disproportionate impact on low income households from GHG emissions insofar as those households are less able to adapt to climate change than high-income households," the work group said.

A Dangerously Polluting Truck

The work group also challenged Pruitt's plan to repeal the emissions standards for so-called "glider" trucks—trucks that are manufactured without engines and later are retrofitted with rebuilt ones.

These have been found to be 40 to 55 times more polluting than new trucks. And although they constitute only 5 percent of heavy-duty vehicles on U.S. roads, if not regulated they would generate a third of the U.S. truck fleet's emissions of smog-forming nitrogen oxides, according to the Obama administration's analysis. Pruitt's planned repeal, announced last November, is opposed not only by environmentalists, but by most of the trucking industry as well as former EPA administrators—both Republican and Democratic.

But it would benefit one manufacturer—Fitzgerald—owned by a politically connected Tennessee family.

EPA's science advisers noted that the agency itself said that "there is uncertainty about what scientific work, if any, would support" the decision to rescind the regulation on glider trucks. In response to a question submitted to the EPA by the work group about its plans for scientific peer review, EPA wrote: "N/A," meaning "not applicable."

The work group said even EPA's assertions that glider trucks cost less than new trucks was without basis, and contradicted by some of the evidence in the record.

"It is clear that this proposed rule is based on claims and assumptions about glider vehicle emissions, safety, and cost that could be assessed via rigorous technical analysis, but it appears that EPA has not attempted to undertake relevant analyses," the work group said.

Jettisoning the Social Cost of Carbon

The work group also urged the Science Advisory Board to review the cost-benefit analysis that underpinned the decision to repeal the Clean Power Plan.

That document, a complex appendix to the final rule, is known as the "regulatory impact analysis," and the Pruitt team manipulated several of its core calculations to justify jettisoning the Obama regulation.

The social cost of carbon was one of the cost-benefit estimates that Pruitt's team radically revised. For example, they skewed the discount rate—the economic formula at the heart of converting future costs to current terms—in a way that converts huge expenses in the distant future to mere pennies on the dollar. That makes it seem as if today's adults should be willing to pay only trivial amounts to head off catastrophic harm to their grandchildren.

This "essentially drives assumed benefits towards zero for the future generations which will be most heavily impacted by current GHG emissions," the work group said. It noted that the National Research Council, in comprehensive reviews of the matter, concluded that such discounting would lead to "much weaker policy than would otherwise be the case."

The Trump administration's reckoning of the social cost of carbon, the work group noted, is 87 percent to 97 percent below previously accepted estimates, "which had been developed and revised over many years by a multi-agency work group of scientists and economists, and was recently subject to extensive reviews by the National Research Council."

The change made by Pruitt's EPA "is not consistent with the NRC recommendations," the group said.

The work group said EPA's new approach of considering only benefits to the United States, and not the world, in its cost-benefit analysis, was a flawed method of analyzing the cost of regulation. "If each country considered only local climate-related benefits of reducing its local GHG emissions, none would act," the work group wrote.

The call to review the science behind Pruitt's attempt to repeal the Clean Power Plan addressed actions on his regulatory agenda early last year.

The work group complained that they had been given "limited information" on a replacement for the regulation, and challenged the EPA's contention that it was "too early in the process" to examine the science behind a draft regulation that is at the White House for review.

The scientific rationale for his changes to regulations on methane, a potent greenhouse gas, also needed to be reviewed, this memo said, because EPA had previously presented scientific findings in support of stricter regulations.

EPA's Science Advisory Board has a long-standing process of assigning work groups to review the adequacy of the science supporting regulatory actions, and to report to the larger board.

The critique from the group is striking because four of the members of the work group are new appointees of Pruitt, including the SAB's new chairman, Michael Honeycutt, who is Texas's chief state toxicologist, and John D. Graham, dean of the School of Public and Environmental Affairs at Indiana University, who was a senior regulatory official in President George W. Bush's White House. It is not clear what sway they will have with the full 44-member board, which includes both Pruitt appointees and holdovers who served during the Obama administration.