In the days after 20 professors fired off a letter urging President Obama to investigate climate skeptics for suspected federal racketeering charges, the climate change movement went into full damage-control mode.

Philip Newell, creative media manager of the public relations firm Climate Nexus, described the Sept. 1 letter as “a big mistake,” advising activists and scientists to downplay the prosecution angle and spin the story away from individuals and toward fossil fuel companies, according to emails obtained Wednesday by The Washington Times.

He cited reports on the skeptics’ website, Climate Audit, saying that although it “isn’t a site to be worried about, it’s definitely looking like this issue isn’t going to go away, even if you remove the letter, which I hear has been done and I would say is a big mistake.”

The letter was first posted on the Institute for Global Environment and Security website and then reportedly removed, but was then posted on other websites.

“I’d recommend you keep it up and point to it as a call for investigating (not prosecuting) organizations and companies (not specific scientists) in an oped or simply a statement on the IGES website that clarifies that distinction,” Mr. Newell said in a Sept. 29 email.

Not everyone has taken that advice. Months later, Virgin Islands Attorney General Claude E. Walker issued subpoenas to ExxonMobil calling for its communications with more than 100 universities, scientists and think tanks, as well as the free market nonprofit Competitive Enterprise Institute.

The latest emails, released in the aftermath of a Virginia open records request filed by the CEI and senior fellow Chris Horner, shed more light on a behind-the-scenes network of academics — some on the government payroll — activists, bloggers and public relations professionals focused on fighting climate change dissent.

The Sept. 1 letter called on Mr. Obama and Attorney General Loretta E. Lynch to launch a “RICO (Racketeer Influenced and Corrupt Organizations Act) investigation of corporations and other organizations that have knowingly deceived the American people about the risks of climate change, as a means to forestall America’s response to climate change.”

Mr. Horner said Wednesday the email shows Mr. Newell and Jagadish Shukla, a George Mason University meteorology professor and co-lead author on the so-called RICO-20 letter, engaged in “spin and deception” to head off criticism over the letter’s implications for free speech.

“When they had the opportunity to define the universe of political opponents — past or present — on whom they sought to sic law enforcement, they did so. It blew up,” Mr. Horner said. “So they turned to spinmeisters to help them convince people to disbelieve their lyin’ eyes when reading the RICO-20 letter.”

He also challenged the argument that the professors directed their attack on companies like ExxonMobil and not others, saying that their “deliberate” word choice indicates that “the only reasonable conclusion is that they sought investigation of all opponents of the political agenda they describe.”

Nearly 200 emails released last month on a judge’s order show Mr. Shukla and fellow George Mason professor Edward Maibach colluding with climate change activists on the letter, then switching to private emails after being hit with the public records request.

The GMU professors said they were inspired by a May 2015 op-ed by Sen. Sheldon Whitehouse, Rhode Island Democrat, who broached the idea of having the federal government pursue fossil fuel companies using civil RICO actions, as was done against the tobacco industry in 1999.

The letter had an immediate impact, although not necessarily in ways its authors had intended. Climate skeptics accused them of trying to chill debate, while the CEI followed up with an open records request of the professors’ communications on their GMU email accounts.

Mr. Newell’s strategic advice came a day after Climate Audit published a Sept. 28 report, “Shukla’s Gold,” accusing Mr. Shukla of double-dipping by drawing paychecks from both George Mason and the IGES, run by he and his wife, which received millions in federal grants to work on climate change research.

Climate Audit reported that the combined IGES salary of Mr. Shukla and his wife Anne amounted to $530,000 in 2004, not including his six-figure professor’s salary. The institute folded in December.

In his email, Mr. Newell recommended changing the narrative on the story, which by then had been picked up by Watts Up With That and other climate websites.

“At this point there needs to be a link people can point to showing that the denier’s ‘Perp walk’ language and the focus on individual scientists is simply not accurate, that your compensation is fair and justified, and that refocuses attention on the real issue: corporate sponsorship of denial,” said Mr. Newell.

His email was addressed to Mr. Shukla, Union of Concerned Scientists science communications officer Aaron Huertas and prominent climatologist Michael Mann, creator of the much-disputed “hockey stick” graph showing an abrupt increase in global temperatures in the 20th century.

In what would appear to be a lucky break for the professors, the RICO-20 letter was posted shortly before InsideClimate News launched a multipart report called “Exxon: The Road Not Taken,” which accused the company of hiding its climate research in order to protect its bottom line.

The emails show InsideClimate News and Climate Nexus had a relationship: On the same day that Mr. Newell laid out his strategy for damage control, InsideClimate News publisher David Sassoon sent an embargoed copy of one of the Exxon stories to six Climate Nexus executives.

“And on that front, you’re in luck because tonight/tomorrow InsideClimate News is publishing the latest in its series about Exxon’s research on climate,” said Mr. Newell in his email. “This one will focus on the legal liability and duty to disclose risk to shareholders, which should be a perfect news hook for you to use if any of you are interested in penning an oped (which I’d be happy to help you with).”

InsideClimateNews and Climate Nexus also share a Rockefeller connection. Climate Nexus is a sponsored project of the Rockefeller Philanthropy Network, while InsideClimate News receives funding from the Rockefeller Brothers Fund and the Rockefeller Family Fund.

The InsideClimate News series, a finalist for the 2016 Pulitzer Prize, was cited as the impetus for AGs United for Clean Power, a coalition of 17 state attorneys general — 16 Democrats and one independent — formed in March to pursue the allegations of “fraud” against climate change dissenters.

New York Attorney General Eric Schneiderman and three other attorneys general have reportedly launched probes into ExxonMobil. Mr. Walker issued subpoenas this year to both Exxon and the CEI, but has since withdrawn his CEI subpoena.

In his email, Mr. Newell also recommended that the professors reach out to publications other than climate blogs in order to prevent “deniers” from driving the narrative.

“Because the deniers have been going nuts with this story but mainstream media largely ignoring and focusing on the Pope, the google-search situation is not good,” Mr. Newell said. “A piece one of the letter signers [wrote] would help with that, and hopefully spur more mainstream coverage to drown out the nonsense.”

He added that, “With the [heat] you’re getting it is probably pretty tempting to try and avoid any further media on this, but I think that’d be the wrong approach that cedes the issue to deniers.”

Previous emails and other documents released by the Energy & Environment Legal Institute show that the idea of using the legal system to pursue climate change dissent dates back to a 2012 workshop held by climate change advocates in La Jolla, California.