One of his elder brothers is politician Lee Hoi-chang, a former Prime Minister of South Korea and a three-time presidential candidate.

[3] Lee was elected as the chair of the Intergovernmental Panel on Climate Change (IPCC) on October 6, 2015.

[6] The landmark Special Report on Global Warming of 1.5 °C (SR15) was released at the meeting on October 8, 2018.

[7][8][9] The highlight of his term as chair, he said in an interview, was personally witnessing numerous world leaders declare their goal of net-zero emissions by mid-century, based on the IPCC reports.

In 2015, The Guardian reported that he has a reputation as a "private, quiet person who listens and gives everyone a chance to speak during meetings".