A new report says India could be 2 degrees Celsius (3.8 F) warmer than 1970s levels within 20 years — a change that would disrupt rain cycles and wreak havoc on the country's agriculture and freshwater supplies, experts said Wednesday.

More flooding, more drought and a spreading of malaria would occur, as the disease migrates northward into Kashmir and the Himalayas, according to the report by 220 Indian scientists and 120 research institutions.

The temperature rise, which could be even more extreme along the coasts, would cause drastic changes in India's rain cycles that threaten water supplies and agriculture — the key source of livelihood for most of India's 1.2 billion people.

The report comes out just weeks before the Nov. 29 start of the U.N. climate summit in Cancun, Mexico, where nations will try again to reach a global agreement to limit greenhouse gas emissions thought to contribute to global warming.

Last year's U.N. climate summit in Copenhagen ended with an international pledge to limit the rise of the Earth's average temperature to 2 degrees Celsius (3.8 F) above levels recorded before industries began pumping carbon dioxide into the air 200 years ago.

The new report by the Indian Network for Climate Change Assessment exceeds U.N. expert predictions that suggested India could be 2 degrees warmer by 2050.

"There is no country in the world that is as vulnerable, on so many dimensions, to climate change as India is," Environment Minister Jairam Ramesh said in a statement released with the report on Tuesday. "We must continue this focus on rigorous climate change science."

India's many ecosystems and proximity to the equator make it particularly sensitive to climate change, experts say. The fact most of the country relies on freshwater sources, rather than desalinating sea water, amplifies the threat of global warming on society.

The report also says sea levels will continue to rise, threatening India's more than 4,000 miles (6,400 kilometers) of coastline.

Mangrove forests along West Bengal's coastlines "would definitely go underwater," said Sidarth Pathak, a climate policy official with Greenpeace India. Coastal cities such as Calcutta, Mumbai and Chennai might also face a threat, he said.

"This study enables India to look at its need to adapt to change," Pathak said. "It will put pressure on the Indian government and international governments to act, and show that India is a vulnerable country."

India has pledged to spend 2 percent of its gross domestic product on projects to deal with the affects of climate change. Activists have said that's not enough, given the challenges in providing water, food and disease prevention to such a large population.

In Cancun, countries are hoping for an agreement that commits nations to curb emissions, to share technologies, and to help poor nations fund projects for coping with a warming planet.