After the Copenhagen climate summit ended with a pledge to raise 100 billion dollars annually by 2020 for developing countries, UN Secretary General Ban Ki-moon decided to form a High Level Advisory Group on Climate Change Financing in early 2010 to work out how this money could actually be mobilized.
On March 5, 2010, the Secretary General named 19 members to this group, and among them was Montek Singh Ahluwalia, who held the post of Deputy Chairman of India's Planning Commission at that time. His selection gave India a voice in shaping how the promised climate funds would be structured and distributed.
Names like Shyam Saran, Chandrashekhar Dasgupta, and Pradipto Ghosh are all associated with India's climate diplomacy in a broader sense, but none of them were the individual chosen for this specific UN advisory panel.
So the Indian personality on Ban Ki-moon's climate financing advisory group was Montek Singh Ahluwalia, confirming option 2.