London, UK Mayor Sadiq Kahn and New York City Mayor Bill de Blasio are urging every major municipality in the world to dump their fossil fuel investments, after C40 Cities released a toolkit to help them do just that.

The toolkit “features an array of case studies from cities around the world that have already committed to ambitious divestment and sustainable investment action, including London, New York, Melbourne, Berlin, and Stockholm,” C40 said in a release.

“We need all cities to act now to help protect our planet for future generations,” Khan said in a statement. “Taking action on divestment is not only achievable but absolutely necessary.”

“With New York City’s Green New Deal, we are leading the nation in fighting the political power and corporate money of the fossil fuel industry,” de Blasio added. “These are not easy steps, but they are absolutely necessary.”

Citing a Khan spokesperson, Reuters says London cut fossil fuels from 1.0 to 0.2% of its pension fund holdings between May 2016 and September 2019. Friederike Hanisch, manager of the 14-member C40 Divest/Invest Forum, said New York’s divestments are “still in progress,” adding that the shift would likely help rather than harm the cities’ return on their investments.

“We don’t expect it to have a negative effect at all on the income of pension funds,” she told Reuters. “If anything, we expect it to have a positive impact.”

The C40 Cities release emphasizes that point. “The toolkit reveals that none of the city pension funds that have already divested from fossil fuel assets report having suffered a negative impact on portfolio performance, and some have seen better performance from their fossil-fuel free investments,” the organization states. It adds that local action steps “can include divesting municipal investments or working with the city or regional pension fund to divest and increase sustainable investments,” as well as calling on private investors and financial institutions to decarbonize their portfolios.

In 2018, University of Massachusetts at Amherst economists Robert Pollin and Tyler Hansen concluded that fossil divestment hadn’t affected companies’ share prices or greenhouse gas emissions, Reuters writes. “But the push is effectively raising awareness of growing climate risks,” and “some coal, oil, and gas companies have said they see the divestment campaign as a ‘material risk’ that could make it harder to source investment.”

That makes city divestment “part of a general trend” that is “making fossil fuel companies sit up and take notice,” said Paul Fisher, a fellow at the Cambridge Institute for Sustainability Leadership at Cambridge University.