BEIJING (Reuters) - The Tibetan plateau, whose glaciers supply water to hundreds of millions of people in Asia, were warmer over the past 50 years than at any stage in the past two millennia, a Chinese newspaper said, citing an academic report.

Temperatures and humidity are likely to continue to rise throughout this century, causing glaciers to retreat and desertification to spread, according to the report published by the Chinese Academy of Sciences' Institute of Tibetan Plateau Research.

"Over the past 50 years, the rate of temperature rise has been double the average global level," it said, according to the report on the website of Science and Technology Daily, a state-run newspaper.

Glacier retreat could disrupt water supply to several of Asia's main rivers that originate from the plateau, including China's Yellow and Yangtze, India's Brahmaputra, and the Mekong and Salween in Southeast Asia.

In May, Chinese scientists said Tibetan glaciers had shrunk 15 percent - around 8,000 square km (3,100 square miles) - over the past 30 years.

The new report said a combination of climate change and human activity on the plateau was likely to cause an increase in floods and landslides there. However, rising temperatures had also improved the local ecosystem, it said.

The scientists urged the government to work to reduce human impact on the region's fragile environment.

But Beijing is building a series of large hydropower projects there, with construction of several mega-dams expected to start by 2020. China has built thousands of dams in the past few decades in a bid to reduce its reliance on imported fossil fuels.

India, too, is planning a number of hydro plants along the Brahmaputra river - more than 100 proposals are under consideration - as the country strives to boost electricity generation.

(Reporting by Stian Reklev and Kathy Chen; Editing by Alan Raybould)