In a statement, his family said Pachauri underwent a major heart surgery before succumbing to his deteriorating health on Thursday.
He passed away at his residence in Delhi.
The environmentalist had suffered a heart stroke in Mexico in July past year, said a source close to him, adding that he was critical and put on ventilator. "Pachauri had also undergone an open heart surgery but his condition didn't improve", said a source, adding that Pachauri was taken home around 7pm on Thursday, where he breathed his last.
TERI, short for New Delhi-based The Energy and Resources Institute, has showed their condolence over Pachauri's demise. Under his leadership, IPCC got the Nobel Peace Prize jointly with former USA vice-president Al Gore.
TERI Director General, Dr Ajay Mathur, who succeeded Pachauri in 2015 in a statement said: "It is with vast sadness that we announce the passing away of Dr RK Pachauri, the Founder Director of TERI".
Current TERI Director-General Ajay Mathur hailed his predecessor's "untiring perseverance" towards establishing the institution.
However, the environmentalist's excellence was overshadowed by a sexual harassment scandal involving a former woman colleague that culminated in his resignation from the prestigious institute in 2015.
"Dr Pachauri's contribution to global sustainable development is unparalleled". An alumnus of the Indian Railways Institute of Mechanical and Electrical Engineering in Jamalpur, Bihar, Pachauri served in various positions in the Indian Railways, including at the Diesel Locomotive Works in Varanasi. A Delhi district court had filed molestation charges against Pachauri in October 2018, though Pachauri denied the charges leveled against him. During the court hearings, the former TERI chief had sought a speedy trial saying he and his family were suffering from hardship since 2015, when an FIR was lodged in the matter.
A Padma Bhushan victor, Pachauri conceptualised and launched the "Lighting a Billion Lives" initiative in 2008, to facilitate clean energy access for all. An FIR was registered against Pachauri on February 13, 2015 and he was granted anticipatory bail in the case on March 21, 2015.