The United Nations Environment Programme (UNEP) is a program of the United Nations that coordinates the organization`s environmental activities, assisting developing countries in implementing environmentally sound policies and practices. In India, the nodal agency for UNEP is the Ministry of Environment, Forest and Climate Change, denoted by Option 1. This is because this Ministry holds primary responsibility for environmental protection, including overseeing forest conservation and policies to combat climate change in India. It is therefore the logical liaison for UNEP in the country.

Option 2, the Ministry of Science and Technology, and Option 3, the Ministry of Earth Sciences, while involved in scientific research and policy making relevant to the environment, are not the primary entities handling environmental matters in India. Lastly, Option 4, the Ministry of Home Affairs, largely concerns itself with internal security matters and is unrelated to environmental policies. Thus, option 1 is indeed the correct answer.