The head of the United Nations climate change panel has stepped down amid sexual harassment allegations in India. Rajendra Pachauri, a Nobel Prize-winning scientist, announced his resignation Tuesday, effective immediately.

Pachauri, 74, has helmed the Intergovernmental Panel on Climate Change (IPCC) since 2002, overseeing the group's regular “assessment reports” that cull the latest scientific data on the causes and consequences of man-made climate change. Its work is deeply influential in ongoing global policy debates over how to reduce greenhouse gas emissions, and by when.

Pachauri on Monday pulled out of a high-level IPCC meeting in Kenya, citing “issues demanding his attention in India,” an IPCC spokesman told BBC News. Indian police are investigating Pachauri after a 29-year-old woman in his Delhi-based research group claimed he harassed her with unwanted emails, texts and phone messages. Pachauri has denied all the allegations.

Ismail El Gizouli, the organization’s vice-chair, was appointed acting IPCC chair Tuesday. “The actions taken today will ensure that the IPCC’s mission to assess climate change continues without interruption,” Achim Steiner, executive director of the U.N.’s Environment Program, said in a statement. “We look forward to a productive session in Nairobi this week.”

The session in the Kenya capital is one of several to take place throughout the year with negotiators from nearly 200 countries aiming to craft a global emissions treaty, which leaders have pledged to adopt at a U.N. conference in Paris this December.

The IPCC’s most recent report found that climate change will cause “severe, widespread and irreversible impacts” on people and the planet unless countries eliminate carbon emissions and stop burning fossil fuels like coal, oil and natural gas. “Science has spoken. There is no ambiguity in the message,” U.N. Secretary General Ban Ki-Moon said at the report’s launch in November. “Leaders must act. Time is not on our side.”

Climate organizations were on the defensive Tuesday morning, insisting that Pachauri’s personal problems were not an indictment on U.N. climate panel itself.

“There will no doubt be some climate change ‘skeptics’ who seek to use Dr. Pachauri’s resignation as an opportunity to attack the IPCC,” Bob Ward, policy director of the Grantham Research Institute on Climate Change and the Environment, said in a statement. He said the IPCC’s latest report “is the most comprehensive and authoritative assessment of the causes and potential consequences of climate change that we have ever had, and that remains true with or without Dr. Pachauri as chair.”