A top House lawmaker’s confrontation with government researchers over a groundbreaking climate change study is provoking a national backlash from scientists, who say his campaign represents the most serious threat Congress has posed to scientific freedom.

Rep. Lamar Smith (R-Tex.), chairman of the House Committee on Science, Space and Technology, has subpoenaed scientists at the National Oceanic and Atmospheric Administration and demanded that they turn over internal e-mails related to their research. Their findings contradicted earlier work showing that global warming had paused, and Smith, a climate change skeptic, has accused them of altering global temperature data and rushing to publish their research in the June issue of the journal Science.

So far, NOAA officials have resisted Smith’s demands, and the showdown has escalated.

The lawmaker has threatened to subpoena Commerce Secretary Penny Pritzker, while scientists have rallied in solidarity with the researchers.

On Tuesday, seven scientific organizations representing hundreds of thousands of scientists sent an unsparing letter to Smith, warning that his efforts are “establishing a practice of inquests” that will have a chilling effect.

“The repercussions of the committee’s actions could go well beyond climate science, setting a precedent to question other topics such as genetically modified organisms and vaccines that have controversial regulatory and policy implications,” the letter said.

The lead signatory was the American Association for the Advancement of Science (AAAS), the country’s oldest and largest general scientific society. Other signers include the American Chemical Society and the American Geophysical Union. The last of several deadlines has now passed for the government to turn over the documents. A legislative aide at the Science Committee said this week that Smith is open to discussions with NOAA to resolve the conflict.

After NOAA Administrator Kathryn Sullivan again balked at the demands on Friday, the aide said the committee still hopes to negotiate with the agency rather than seek contempt charges. In a letter to Smith, Sullivan defended her agency’s work, saying her staff is not influenced by political interference.

“I have not or will not allow anyone to manipulate the science or coerce the scientists who work for me,” she wrote.

The committee’s top Democrat, Rep. Eddie Bernice Johnson (D-Tex.) has called Smith’s investigation a “partisan witch hunt.”

Humans’ staggering effect on Earth

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At the center of the feud is a report that appeared in the June 4 online edition of Science, a peer-reviewed journal. The NOAA scientists cited improved, more accurate measurements of global temperatures on land and sea to refute the notion of a warming hiatus, striking at the heart of an argument by climate change skeptics.

NOAA manages one of the world’s most significant archives of oceanic, atmospheric and geophysical data, and its global temperature data is used by scientists worldwide.

Smith has alleged that NOAA researchers used inaccurate data or even manipulated it to promote President Obama’s agenda on climate change. Smith shifted tactics last week, alleging that the research was rushed and citing what he says is information provided by agency whistleblowers showing that some employees at the agency were concerned that it was premature to publish the study.

The lawmaker and committee aides have noted that the study was published two months before the Obama administration announced its Clean Power Plan, which aims to cut carbon emissions from power plants, and five months before this month’s climate summit in Paris.

The researchers may have violated the agency’s scientific integrity standard, Smith suggested.

“Their agenda comes first, and the facts come second if at all,” he said in a speech last week to the Texas Public Policy Foundation in Austin. He denounced the president’s climate agenda as “suspect.”

“The science is clear and overwhelming but not in the way the president says,” Smith said. “NOAA employees altered historical climate data to get politically correct results.”

But a spokeswoman for Science said in an interview that the NOAA scientists’ research was subject to a longer, more intensive review than is customary.

“This paper went through as rigorous a review as it could have received,” said Ginger Pinholster, chief of communications for AAAS, which publishes Science. “Any suggestion that the review was ‘rushed’ is baseless and without merit.”

She said the report, submitted to the journal in December, went through two rounds of peer review by other scientists in the field before it was accepted in May. The number of outside reviewers was larger than usual, and the time from submission to online publication was about 50 percent longer than the journal’s average of 109 days, Pinholster said.

During the review, the research was sent back to NOAA for revision and clarification, she said. And because it was based on such an “intensive” examination of global temperature data, the reviewed was handled by one of the journal’s senior editors, she said, “so it could be more carefully assessed.”

For scientists, the concern over Smith’s investigation goes beyond the issue of global warming. They say his efforts are a threat to the independence of the sometimes-messy and painstaking process of discovery.

“This is not just a few scientists grousing about somebody besmirching the work of a group of scientists,” Rush Holt, chief executive officer of the AAAS, said in an interview. “It’s an affront to the scientific process.”

With the threat of a congressional subpoena now hanging over the head of every scientist, “people will start worrying, ‘did I say something wrong in a conversation with a colleague?’ ” said Holt, a former Democratic congressman from New Jersey. “This is not a small matter.”

Scientists also warn that Smith’s efforts raise concerns for NOAA and other federal agencies, which may now worry about jeopardizing their federal budgets if they get in the crosshairs of a lawmaker who disagrees with their work.

“Now you’ve got somebody who has congressional subpoena power doing this, who can continue to investigate and investigate a particular agency because they don’t like a given result,” said Andrew Rosenberg,  director of the Center for Science and Democracy at the Union of Concerned Scientists. “They can carry it over in appropriations.”

Rosenberg’s group sent a letter of support Tuesday to Sullivan signed by two dozen former senior NOAA scientists. Staff members on the House Science committee have declined to detail the information provided by  whistleblowers, saying this would identify individuals who want to remain anonymous.

But pressed for more specifics, the staff has pointed as an example to new temperature data that was made publicly available earlier this month and questioned how the scientists used it. The data came from a larger number of measuring stations around the world than previous data sets.

“NOAA should not be publishing headline-grabbing results based on data sets that have not been adequately vetted and were not available to the public,” an aide to the House committee said.

“This isn’t an easy high school science experiment where you do it and you get results and write them up,” another aide said. “There are huge data sets from all over the world. They need to be studied. Every time the sets are changed they have to be worked on to make sure the data set is now valid.

The scientists, however, say their research was based on an earlier version of the data that had been made public and examined by other climate experts. The study published in Science was not based on the updated data released earlier this month, although the two versions are very similar, according to NOAA officials and one of the study’s authors.

That author, Thomas Peterson, described in an interview some of the tensions at NOAA between the scientists and computer engineers who were writing software code for the data and wanted more time to make sure it was reliable. The scientists felt confident using the data that had already been made public and were ultimately vindicated by the latest version.

The conclusions of the Science report were based on corrections and adjustments to even earlier land and sea temperature measurements. These were intended to address what scientists described as measurement biases in readings taken of ocean temperatures and land temperatures that did not fully account for the rapidly warming Arctic.

NOAA published the first updates to the land temperature data set in October 2013 in the Geoscience Data Journal. The revised sea surface data were published in the Journal of Climate in October 2014. These updates were the basis of the study in Science, NOAA officials said.

That combined data set was available publicly in July 2014, officials said.

As NOAA scientists examined the data, they discovered that warming trends over the past few decades would be substantially larger than what the earlier data set indicated, recalled Peterson, who retired from NOAA as principal scientist in July.

“Was there a rush to get [the research] out? No,” he said. “Did we want to get this out to advance the science? Of course.”