Harvard affiliates are planning a weeklong sit-in protest around Massachusetts Hall this April to demand that the Harvard Corporation—the University’s highest governing body—divest Harvard’s endowment from fossil fuels.

In an open letter posted online early Friday morning, more than two dozen alumni called for fellow University graduates to gather in Harvard Yard for the protest that organizers are calling “Harvard Heat Week.” The event website, created by the activist group Divest Harvard, calls for 50 to 100 people to participate in each day of the sit-in, which is scheduled to begin on April 13 and culminate with a “major event” on April 18.

Just last week, more than 30 students from Divest Harvard occupied Mass. Hall, some for 24 hours, calling on University President Drew G. Faust to divest. Harvard’s endowment is valued at $35.9 billion.

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In April, activists plan to engage in “highly civil civil disobedience,” both locally through the sit-in demonstration around Mass. Hall and remotely through social media, phone, and email, according to the open letter. Its signatories include filmmaker Darren S. Aronofsky ’91, Nobel Peace Prize winner Eric S. Chivian ‘64, Pulitzer Prize winner Susan C. Faludi ’81, actress Natalie Portman ’03, activist-author Cornel R. West ’74, and former Colorado Senator Timothy E. Wirth ’61.

Despite emphasizing the plan to protest “peacefully and politely but firmly,” the letter hinted at the potential for police intervention. “If anyone is to be led away by the University Police, surely it’s easier for those of us with stable and secure lives than for students at the start of their careers,” the alumni signatories wrote.

According to the “Heat Week” website, all protesters must attend a non-violence training and an action briefing before participating in the sit-in.

The alumni will work alongside Divest Harvard, which has been advocating divestment on campus for more than two years, to implement the week of programming. Chloe S. Maxmin ’15, Divest Harvard student outreach coordinator and co-founder, said  she expects more than 100 alumni to participate.

“Since we’ve begun to escalate and get more serious with the action, we’ve been planning this coalition week with alumni,” Maxmin said. “It was a mutual effort to push it forward, but we’re very grateful that alumni are coming to support students on campus.”

Faust, despite the urgings of student activists, has maintained that Harvard will not divest from fossil fuels. She has argued that Harvard can contribute to environmental sustainability and reduce fossil fuel dependence through research and teaching. Last week, her Climate Change Solutions Fund awarded $800,000 in grants to Harvard affiliates for projects focusing on climate change.

Divest Harvard, meanwhile, has continued to push for their cause. The group announced plans to launch a fossil fuel-free fund, which seeks alumni donations as an alternative to the University’s endowment, earlier this month.

The open letter’s full list of signatories includes Craig S. Altemose, filmmaker Darren S. Aronofsky ’91, Charles “Al” Boright ’68, Rev. Margaret M. Bullitt-Jonas, Nobel Peace Prize winner Eric S. Chivian ’64, Pulitzer Prize winner Susan C. Faludi ’81, H. Jack Geiger, Todd A. Gitlin ’63, Neva R. Goodwin ’66, Rev. Dr. Ray A. Hammond ‘71, Jon T. Isham ‘82, Robert F. Kennedy, Jr. ’76, Maya Lin, Bevis Longstreth, Robert K. Massie, Edwin S. Matthews ’56, Timothy P. McCarthy ’93, Bill E. McKibben ’82, Ricken S. Patel, actress Natalie Portman ’03, former member of the Harvard Board of Overseers Gay W. Seidman ’78, Rev. Fred E. Small, Rev. Dan Smith, Rev. Betsy J. Sowers, Rev. Burns Stanfield, Wen Stephenson ’90, Rhea S. Suh ’98,  Rev. Elizabeth A.  Walker, Cornel R. West ’74, Rev. Dr. Gloria White-Hammond, Kelsey D. Wirth ’92, and former Colorado Sen. Timothy E. Wirth ’61.

—Staff writer Mariel A. Klein can be reached at mariel.klein@thecrimson.com. Follow her on Twitter @mariel_klein.