The leader of the U.N.'s expert panel on climate change stepped down on Tuesday amid an investigation into a colleague's allegations of sexual harassment.

Rajendra K. Pachauri, 75, an Indian citizen, had chaired the Intergovernmental Panel on Climate Change since 2002 and accepted the 2007 Nobel Peace Prize on its behalf.

The IPCC "needs strong leadership and dedication of time and full attention by the chair in the immediate future, which under the current circumstances I may be unable to provide," Pachauri wrote in a letter to U.N. Secretary-General Ban Ki-moon.

He did not elaborate, but pointed to his withdrawal from a meeting in Nairobi this week to attend to what the IPCC called "issues demanding his attention in India."

Pachauri is being investigated in India after a 29-year-old woman accused him of sexually harassing her while they worked together at the New Delhi lobbying and research organization he heads, The Energy Resources Institute.

A police report said the woman gave police dozens of text messages and emails that she alleged had been sent by Pachauri. A Delhi court on Monday ordered Pachauri to cooperate in the investigation.

Pachauri denies the allegations and has said he is "committed to provide all assistance and cooperation to the authorities."

Police said they would question a second woman who also accused Pachauri of sexual harassment but had not filed a police report.

The IPCC said its vice chairman, Ismail El Gizouli, will serve as its acting chairman, and a vote on a new head was already scheduled for October. Pachauri's second term as chairman was due to end then, and he had said that he wouldn't run for a third term.

Pachauri said in his resignation letter that he "would be available for help, support and advice to the entire IPCC in its future work in whatever manner I may be called on to provide."

He has also taken leave from his position at the lobbying group, it said in a statement Tuesday.

The accusations against Pachauri have caused outrage in India, where women face a stigma against discussing issues such as sexual harassment in the workplace.

Several recent high-profile cases suggest, however, that women are beginning to feel more comfortable going public with reports of sexual assaults — an important breakthrough in a country where men feel emboldened to commit crimes because they know women experience such a stigma.

In 2013, an editor of an Indian magazine known for exposing abuses of power was arrested after a young female colleague accused him of sexually assaulting her in a hotel elevator during a conference.