In the hours before they took the stage for their March 29 press conference, Democratic attorneys general received a secret briefing from two top environmentalists on pursuing climate change dissenters.

Peter Frumhoff of the Union of Concerned Scientists and the Climate Accountability Institute’s Matt Pawa spent 45 minutes each providing talking points behind the scenes on “the imperative of taking action now” and “climate change litigation,” according to a cache of emails released over the weekend by the free market Energy & Environmental Legal Institute.

For climate change groups, the New York press event was the culmination of four years of planning and advocacy in support of an explosive proposition: using the legal system to link fossil fuel firms and others challenging the catastrophic global warming consensus to fraud and even racketeering, the emails and other documents show.

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The effort paid off. At the press conference, which included former Vice President Al Gore, a coalition of 16 Democratic attorneys general and one independent — Virgin Islands Attorney General Claude E. Walker — announced that they would use the power of state government to explore legal avenues to challenge climate change dissent.

Four of the attorneys general have reportedly launched investigations into Exxon Mobil Corp., and Mr. Walker has issued a subpoena for 10 years worth of climate change documents and communications from the Competitive Enterprise Institute, a free market think tank.

Mr. Walker also issued a subpoena last month to Exxon Mobil, citing the territory’s laws against racketeering. The company filed a motion Wednesday to block the subpoena in Texas state court.

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David Schnare, legal counsel for E&E, called on the coalition, operating under the name AGs United for Clean Power, to reveal its relationship with the climate change movement.

“We call on these AGs to immediately halt their investigation and lay out for the public the full extent of this collusion, producing all records or information provided them in briefings or other work with the outside activists, including those they are trying to keep secret through a Common Interest Agreement,” Mr. Schnare said in a Friday statement.

He highlighted a March 30 email from Mr. Pawa telling two members of New York Attorney General Eric Schneiderman’s staff about a call from a Wall Street Journal reporter about his attendance at the press conference.

Mr. Pawa asked, “What should I say if she asks if I attended? No comment?”

Lemuel Srolovic, environmental protection bureau chief for the New York attorney general, advised Mr. Pawa to say nothing about his participation.

“My ask is if you speak to the reporter, to not confirm that you attended or otherwise discuss the event,” Mr. Srolovic says in the email.

Mr. Pawa said in a Sunday email to The Washington Times that it is “inaccurate in attributing to me the idea that lawsuits should be used to achieve political outcomes.”

“I have always been consistent in my position that lawsuits should be brought to remedy legal wrongs,” Mr. Pawa said in an email.

The New York attorney general’s office told Reuters that it routinely seeks input from outside organizations but pursues cases based only on the merits.

The push for legal action against climate change dissent dates back to June 2012 when climate groups held a workshop, Establishing Accountability for Climate Change Damages: Lessons from Tobacco Control, at the Scripps Institution of Oceanography in La Jolla, California.

Last year, a coalition of environmentalists and lawmakers led by Sen. Sheldon Whitehouse, Rhode Island Democrat, petitioned the Justice Department to file a racketeering lawsuit against “corporations and other organizations that have knowingly deceived the American people about the risks of climate change.”

The collection of emails sheds new light on the close working relationship between the climate change movement and Democratic lawmakers.

The emails were obtained under the Vermont Public Records Law. Vermont Attorney General William Sorrell’s office helped Mr. Schneiderman’s staff organize the event.

In a March 30 email, Vermont Assistant Attorney General Scott Kline recommended changing the name of the Exxon/Fossil Fuel Company Investigations working group by removing the word “investigations.”

“Not all of the states have yet opened a formal investigation and there is some sensitivity here (and I suspect in some other states) to saying or indicating we have,” Mr. Kline said in an email to Mr. Srolovic.

He also recommended removing the word “progressive” from the “Climate Coalition of Attorneys General Pledge,” which originally stated, “We pledge to work together to fully enforce the State and federal laws that require progressive action on climate change and that prohibit false and misleading statements to the public, consumers and investors regarding climate change.”

Elsewhere, Mr. Kline objects to an effort by Mr. Schneiderman’s office to enter into a common interest agreement that would enable the coalition’s communications, including those with outside groups, to be protected by the privilege and thus exempt from public disclosure laws.

“Our thought has been that anyone providing anything in writing at the conference should assume that it may get produced because of some state’s public records laws,” Mr. Kline says in a March 28 email. “Matt and Peter should stick to what is in the public domain or be prepared to have those materials become public.”

Mr. Schnare said the emails “show Schneiderman’s office suggested their outside-activist green allies deceive the press; meanwhile, AGs in his coalition have subpoenaed at least one policy group’s correspondence with the media.” His reference was to the Competitive Enterprise Institute.

Joining Mr. Schneiderman, Mr. Sorrell and Mr. Walker at the press conference were Attorneys General George Jepsen of Connecticut, Brian E. Frosh of Maryland, Maura Healey of Massachusetts and Mark Herring of Virginia.

“As we all know, global warming, if not reversed, will be catastrophic for our planet,” said Mr. Sorrell. “We, the states, have a role to play in this endeavor and intend to do our part.”

Several Republican attorneys general have called the coalition’s effort an attack on free speech.

“This scientific and political debate is healthy, and it should be encouraged,” said a March 30 joint statement by Attorneys General Scott Pruitt of Oklahoma and Luther Strange of Alabama.

“It should not be silenced with threats of criminal prosecution by those who believe that their position is the only correct one and that all dissenting voices must therefore be intimidated and coerced into silence,” they said. “It is inappropriate for State Attorneys General to use the power of their office to attempt to silence core political speech on one of the major policy debates of our time.”

Both have joined a lawsuit filed by 26 attorneys general challenging the EPA’s Clean Power Plan, which requires strict emissions reductions in the name of combating climate change.