Actress Natalie Portman, environmentalist Robert F. Kennedy, Jr., and other high-profile Harvard University alumni are calling for demonstrations to urge divestment from fossil fuels.

Organizers of “Harvard Heat Week” are planning events of “highly civil civil disobedience,” including daily sit-ins for the week of April 13, according to a letter released Friday asking alumni to come to the campus in Cambridge, Massachusetts, to join the effort.

Comparing their cause to 1980s campus protests against South Africa’s former apartheid policy, students at Divest Harvard have been calling for the school’s $36.4 billion endowment to end investment in oil, gas and coal because of their environmental impact.

President Drew Faust has declined to commit to divestment, saying the endowment isn’t an instrument of political change. Students occupied her office earlier this month for about 24 hours.

“We need to have action on climate change and climate justice immediately,” said Naima Drecker-Waxman, 18, a freshman helping to organize the event. “A lot of campuses across the country have decided this is a spring for escalation.”

Harvard recognizes that climate change is among the world’s most urgent challenges, said Jeff Neal, a spokesman. The university is strengthening its role in research and education to help address the issue, he said in an e-mail.

Stanford Activism

Stanford University, near Palo Alto, California, said last year it would end its investments in coal companies, a decision that gave momentum to environmental activists. Stanford said at the time there are alternatives to coal that have less impact on the environment.

Among the 31 other people who signed the letter are former U.S. Democratic Senator Tim Wirth of Colorado; 1985 Nobel Peace Prize winner Eric Chivian; Robert Massie, founder of the Investor Network on Climate Risk; and Maya Lin, who designed the Vietnam Memorial in Washington and received an honorary degree from Harvard.

“We will come to the Yard in the spring filled not with rancor but with hope,” the letter reads. “Please join us.”

Drecker-Waxman said she couldn’t confirm that all those who had signed the letter would participate in the demonstrations.

“We’re grateful to have their support,” she said.

Copyright 2015 Bloomberg

Lead image: Harvard gates via Shutterstock