Joe Biden rolled out twin endorsements Wednesday intended to bolster his environmental credentials on the 50th celebration of Earth Day, receiving nods from two of the party’s most established voices on combating climate change: former vice president Al Gore and Washington Gov. Jay Inslee.

“I would just say plainly and simply, this is not complicated,” Gore said in a 30-minute virtual conversation with the presumptive Democratic presidential nominee. “If you care about the climate crisis, if you want to start solving the climate crisis, this is not rocket science.”

He called President Trump “the face of climate denial globally.”

Gore raised the alarm early on climate change, describing the threat to the planet in his 1992 book “Earth in the Balance.”

Inslee’s endorsement was unveiled earlier in the day via Biden’s occasional “Here’s the Deal” podcast, which also largely focused on climate change.

“You need to act early, and we need bold leadership to do that,” said Inslee (D), who helped establish the initial climate change caucus as a member of Congress in the late 1990s. “That’s why I’m looking forward to your leadership in the White House on this.”

Inslee focused his presidential campaign last year on the importance of reducing carbon emissions and addressing climate change. He never gained momentum with voters, but he was applauded by activists for drawing attention to the issue.

Biden has faced skepticism from some in the environmental movement, especially after a Reuters report that he was seeking a “middle ground” on climate policy. He insisted that he takes the issue seriously. During the primaries, environmentalists have urged him to more fully embrace initiatives such as the Green New Deal, which seeks to dramatically cut the country’s use of fossil fuels and sharply reduce greenhouse-gas emissions.

Many conservatives call the Green New Deal extremist and its supporters alarmist, saying its far-reaching goals amount to overkill. Ultimately, Biden released a climate plan that followed the Green New Deal’s framework but stopped short of full-throated support for it.

For example, Biden’s plan allows for longer timelines on decarbonizing the U.S. economy and it does not specify exactly how enforcement would work.

The Sunrise Movement, a liberal group pushing Democrats to be more aggressive on climate change, gave Biden 75 points out of 200 on its issue scorecard. In comparison, Sen. Bernie Sanders (I-Vt.) earned 183 points.