By Nita Bhalla

NEW DELHI (Reuters) - India is likely to suffer more than most countries as a result of climate change, with poor agricultural output, more natural disasters and increased deaths due to higher occurrence of diseases, the author of an acclaimed report on global warning said on Wednesday.

Former World Bank chief economist Nicholas Stern's report on the economic impact of climate change said unchecked greenhouse gas emissions would see global temperatures rise by 2-3 degrees centigrade in the next 50 years.

Speaking to Indian businessmen, Stern said the annual June-September monsoon rains, which India is heavily dependent on for its crop production, would impact the economy.

"There could be more variable starting dates (for the monsoon). There could be periods of much greater intensity and there could be quite extended periods of no rain. But it is likely to be disrupted," he said.

"It's clear India will suffer like the rest of the world, perhaps more that the rest of the world."

Experts estimate a temperature rise of between 2 and 3.5 degrees centigrade, would cost India a loss of between nine and 25 percent of total agricultural revenue. Agriculture makes up around 22 percent of India's gross domestic product.

Stern said temperature rises would also mean vector-borne diseases like malaria and dengue fever spreading to higher altitude regions known for being free of mosquitoes.

As a result, there was a likelihood of more deaths that would result in lower productivity, he said.

The head of Britain's Economic Service said the melting of Himalayan glaciers would mean neighboring Bangladesh could experience serious floods as a result of rising sea levels, sparking mass migration across the border into India.

He said the flow of water from the glaciers would be curtailed during India's dry season and would have "serious consequences".

Experts say melting glaciers will affect one-sixth of the world's population residing mainly in the Indian subcontinent. India's Ganga River receives 70 percent of its summer water flow from the Himalayan glaciers and sustains over 500 million people.

Stern said India was making progress in adapting to the challenges faced in curbing emissions and investing in clean development mechanisms. But climate change was an inequitable process in which rich nations had to take the burden of responsibility, he said.

"This is a doubly inequitable process as it's the rich countries that are responsible for 75 percent of the greenhouse gases that are up there and it's the that will be hit earliest and hardest," he said.

"All countries must be involved, but equity demands that the rich countries bear the big majority of the cost."