Avengers: Endgame star Mark Ruffalo took to Twitter on Monday to promote his own Marvel licensed t-shirt, for which proceeds go toward the “fight for climate justice.”

Ruffalo, who played the role of Bruce Banner and The Incredible Hulk in the blockbuster film franchise, urged his followers to “act fast” in purchasing the t-shirt, which declares the battle against climate change as “the fight of our lives.”

The Limited Edition Charity T-shirt costs $39.99 and is officially licensed by Marvel. Proceeds from the shirt’s sale go toward The Solutions Project, an organization co-founded by Ruffalo with the aim of promoting the use of 100 percent clean energy by the year 2050.

“Oh snap, there’s only 1 day left to grab this # AvengersEndgame tee on @Represent,” the Spotlight actor wrote on Twitter. “100% of proceeds go to The Solutions Project (@100isNow) to fight for climate justice. Remember there are no second chances with this one so you better act fast!”

Oh snap, there's only 1 day left to grab this #AvengersEndgame tee on @Represent. 100% of proceeds go to The Solutions Project (@100isNow) to fight for climate justice. Remember there are no second chances with this one so you better act fast! https://t.co/yFPxv1n0rq pic.twitter.com/HJaU6QncaD — Mark Ruffalo (@MarkRuffalo) May 20, 2019

Other Marvel movie stars have used their massive social media platforms to promote Ruffalo’s campaign.

Saw a few friends from work rocking some limited edition #AvengersEndgame t-shirts and supporting @100isnow’s commitment to climate justice. Grab a shirt today ➡️ https://t.co/xGclrhXtHM pic.twitter.com/szXsdYdR94 — Mark Ruffalo (@MarkRuffalo) May 1, 2019

According to The Solutions Project website, Ruffalo provides the organization with “Cultural Leadership” as they pursue their “50 state transition plan” aimed at encouraging people across the U.S. to get their energy from wind and the sun.

Mark Ruffalo has long gained attention for his environmental activism. Last month, he and fellow Avengers star Don Cheadle wrote an op-ed in The Hill declaring that only “radically feminine leadership” can “save our planet” from the effects of climate change, adding that they want to use their “positions of privilege to support and learn from women leaders as they make history.”

“Climate change is among the most urgent crises our new leaders face,” they wrote. “From wildfires, hurricanes, and droughts to cancer and asthma, the effects of dirty energy and climate change affect us all. Unfortunately, those already vulnerable — children, the elderly and those living in poverty, are hit hardest.”

In October 2016, Ruffalo also challenged President Barack Obama’s record on climate change, accusing him of being an “immoral” hypocrite for referring to himself as a “climate change leader.”

“President Obama, it is immoral for you to keep drilling in our state lands, in our federal lands, off our federal waters, while at the same time calling yourself a climate change leader,” he said at a rally in Los Angeles with actress Susan Sarandon.

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