The League of Conservation Voters called on Donald Trump’s three oldest children on Thursday to ensure that their father protects the environment, citing an open letter they and the president-elect signed in 2009 urging President Obama to act on climate change.

Thursday’s letter — which was signed by LCV President Gene Karpinski and the chair of LCV’s board of directors, Carol Browner, who served as Obama’s climate czar during his first term — highlights the extent to which environmentalists are concerned about the direction of the next administration. On Wednesday, more than 2,300 scientists, including 22 Nobel laureates, sent a letter to Trump and GOP congressional leaders urging them to respect scientific integrity once they take the helm of the executive and legislative branches in January.

Hours after LCV sent its letter to Trump’s children, a coalition of 30 green groups sent every member of the Senate a letter arguing that they should only support Cabinet nominees next year if they are committed to key environmental safeguards.

Noting that the incoming president had vowed to unify the country, they write, “A critical step forward would be for him to nominate Cabinet secretaries and agency heads who are committed to addressing the climate crisis and to protecting our air, water, health, public lands and wildlife.”

“If the President-elect instead chooses to nominate individuals who deny climate science or would seek to gut our bedrock environmental protections or roll back recent climate progress, we urge you to vote against their confirmation,” adds the signatories, which include the National Parks Conservation Association, Ocean Conservancy and the Sierra Club.

For their part, Karpinski and Browner note that the four Trumps signed a letter addressed to Obama and published in the New York Times in November 2009 that cautioned, “If we fail to act now, it is scientifically irrefutable that there will be catastrophic and irreversible consequences for humanity and our planet.”

“Seven years later the stakes have never been higher in the global fight against climate change,” Karpinski and Browner write in Thursday’s letter.

None of Trump’s children spoke extensively about the issue of climate change during the campaign, though Donald Trump Jr. and Eric Trump are avid hunters. Donald Jr. told a group at the Theodore Roosevelt Conservation Partnership’s meeting this summer that the campaign had “broken away from a lot of traditional conservative dogma on the issue, in that we do want federal lands to remain federal,” a position his father outlined in a Field & Stream interview nearly a year ago.

The Trump campaign could not be reached for comment Thursday.

On the question of climate change, however, the president-elect has given little indication that he will pursue the kinds of policies that LCV and other groups support. Donald Trump has vowed to boost fossil fuel production in the United States, particularly within the coal industry, and at a town hall meeting in New Hampshire during the GOP primaries, he mocked the idea that global warming is a threat. At that event, LCV volunteer Meghan Andrade asked Trump what he would do to address the issue, to which he replied: “Let me ask you this — take it easy, fellas — how many people here believe in global warming? Do you believe in global warming?”

After asking three times “Who believes in global warming?” and soliciting a show of hands, Trump concluded that “nobody” believed climate change was underway except for Andrade.

“Well, it’s a very interesting” question, Trump said. “You believe, right? You believe?”

Referring to that incident, Karpinski and Browner write, “On Election Night, your father said he wants to be a president for all Americans. It’s pretty simple. For your children’s future and the future of all Americans, we must honor the United States commitments under the Paris agreement and reduce greenhouse gas emissions at least 80 percent below 2005 levels by 2050, and we must defend the Clean Power Plan, the single largest step our nation has taken to address climate change.”

They also specifically point to some of those being considered by Trump to head key environmental agencies or to serve as top advisers — including the Competitive Enterprise Institute’s Myron Ebell, former Alaska governor and GOP vice-presidential nominee Sarah Palin and former Texas Commission on Environmental Quality chair Kathleen Hartnett White — as people who “should make it nowhere near his administration. Our planet simply can’t afford to give polluters free rein to pollute our air and water and even sell off public lands.”

It is unclear how much leverage the nation’s environmental groups — including LCV, which endorsed Hillary Clinton for president before a single primary ballot was cast and spent $10 million in an effort to help her win the White House — have when it comes to Trump or his three oldest children, who serve as some of his top advisers.