Paul McCartney, Lumineers, 'Avengers' & More Celebrate Earth Day Declaring #ClimateChangeIsReal

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Paul McCartney performs during the Out There tour at the United Center on July 9, 2014 in Chicago, Illinois. 

Musicians including Paul McCartney, the Lumineers and Brazil's Jota Quest have teamed with an impressive roster of celebrities, politicians, NGOs and multinational companies to raise awareness over climate change this Earth Day, tweeting out the message #ClimateChangeIsReal on Tuesday. 

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Also participating are President Barack Obama, Brad Pitt, Mark Ruffalo and Avengers director Joss Whedon, as well as companies including Nike, Unilever and Virgin to help get the hashtag trending in the United States and reaching more than 175 million people on social media, each with their individual takes and solutions.  

McCartney used the occasion to promote his global Meat Free Monday initiative, stating, "eating less meat is a real way to help."

Meanwhile, Lumineers and Jota Quest had their own takes, and Sarah Lee Guthrie and Johnny Irion and Nada Surf's Matthew Caws wrote new songs for the occasion:



Other artists are participating in other mediums through Creative Climate and the is acting as a hub for participating social posts.