Reuters Actors Bradley Cooper (left), Juliette Binoche (center) and Jude Law (right) were among the signatories of the pointed open letter.

Two hundred actors, musicians, artists and scientists have banded together to issue a fervent plea to world leaders to act “firmly and immediately” to address climate change.

Without prompt and courageous political action, the famous group warned in an open letter published Monday in the French daily Le Monde, “global catastrophe” will be imminent.

“It is time to get serious,” the letter’s signatories declared, according to a France24 translation. “The sixth mass extinction is taking place at unprecedented speed. But it is not too late to avert the worst.”

notre tribune, initiée par mon collègue et ami @AurelienBarrau publiée dans @lemondefr d'hier soir:



"Le plus grand défi de l’histoire de l’humanité" pic.twitter.com/MvSJfrEAJ6 — herve_dole (@herve_dole) September 4, 2018

The signatories included French and American actors and musicians like Ethan Hawke, Juliette Binoche, Alain Delon, Bradley Cooper, Patti Smith, Jane Birkin, Willem Defoe, Jude Law, Ralph Fiennes and Marion Cotillard.

Several acclaimed scientists, including astrophysicist Aurélien Barrau, climatologist Jean Jouzel, and mathematician Mikhaïl Gromov, also signed the plea.

The letter’s publication follows the resignation of France Environment Minister Nicolas Hulot, who announced last week that he was quitting after feeling “all alone” on environmental issues.

200 of world’s most prominent artists and scientists have signed an open letter in France's Le Monde calling politicians to “firmly and immediately” tackle climate change and “collapse of biodiversity”https://t.co/e77JpB5Iqz pic.twitter.com/UDDQwGtSXi — Leo Hickman (@LeoHickman) September 3, 2018