The fossil fuel divestment movement has doubled over the past 15 months, with the value of assets held by divesting institutions and individuals now exceeding $5 trillion, according to a new report from Arabella Advisors.

Pension funds and insurance companies now represent the largest sectors committing to divestment, the report said.

"A growing recognition by the financial sector of the threat of stranded carbon assets is becoming a pressing fiduciary issue and may drive a new wave of commitments," the investment advisors said in their annual report on divestment. Assets are considered stranded if they lose their value before the end of their economic life.

In June, the U.N. Environment Programme Finance Initiative and Principles for Responsible Investment released a paper that concluded, "Failing to consider long-term investment value drivers, which include environmental, social and governance issues, in investment practice is a failure of fiduciary duty."

The $5 trillion figure represents the total assets owned by the divesting institutions — or assets under management for financial institutions — not the amount they are diverting from fossil fuels.

A list of companies that have fully or partially divested fossil fuels can be found here.