Over 80 scientists, including prominent climate experts, are out with an open letter endorsing Joe Biden just ahead of the 50th anniversary of Earth Day.

Why it matters: The letter comes as Biden is seeking to consolidate support among progressives who prefer Sen. Bernie Sanders' more aggressive climate platform.

What they're saying: "We are confident that, unlike President Trump, Joe Biden will respect, collaborate with, and listen to leaders in the scientific community and public health experts to confront the existential climate crisis and other environmental threats," the letter states.

"Biden’s plan to address climate change leads with science and facts and pledges U.S. leadership on climate action," it states.

Who they are: Signatories include the prominent Penn State climate scientist Michael Mann and Jane Lubchenco, who ran NOAA under former President Obama.

Catch up fast: Biden yesterday signaled that he plans to expand his climate platform. And Sanders' endorsement of Biden last week included the announcement of plans to form joint policy "task forces," with climate among the topics.

Go deeper: Joe Biden signals expanded climate plan as a "key objective"

Editor's note: This story has been updated as more scientists have signed onto the letter.