科学与发展网络(SciDev.Net)

Studies indicate the Indian summer monsoon is already weakening

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[NEW DELHI] Freshwater melting from Greenland's ice sheet could weaken the Indian monsoon to the extent of threatening perpetual drought, one of India's leading climate scientists has warned.

Bhupendra Nath Goswami, director of the Indian Institute of Tropical Meteorology (IITM), Pune, told a media workshop on climate change last week (27 August) that the Greenland ice melt will add more freshwater to the north Atlantic Ocean, making it less saline.

This could weaken both the circulation of ocean waters and temperature variations over the Indian subcontinent — two key factors that could also weaken the Indian summer monsoon, says Goswami.

The IITM has carried out several simulations of the effects of increased freshwater in the north Atlantic Ocean on the monsoon that give rise to concern, says Goswami.

Other studies by the Centre for Atmospheric Sciences at the Indian Institute of Technology, Delhi, indicate that the Indian summer monsoon is already weakening (see Indian summer monsoon weakening, say scientists).

The possibility of the monsoon failing to relieve drought in 50–60 years time "cannot be discounted", Goswami told SciDev.Net. But he adds that the projections are unreliable as current models are unable to simulate monsoon rainfall and climate accurately.

His team reported in April that monsoon weather has already become almost twice as difficult to predict than in previous years and that climate change will make it even more unpredictable (see Global warming may make monsoons harder to predict).

Accurate predictions require better observation and models, and high computational power, Goswami says. India's ministry of earth sciences is rapidly improving computer infrastructure but it is "still subcritical".

"We are talking about 1,000 times larger than present capacity," he says.

Goswami also says that the India's climate modelling community "is small and not quite ready for the computing required for climate change".

Shailesh Nayak, secretary of the ministry of earth sciences, stressed at the workshop the need for more studies on the impact of climate change on the monsoon. "We have been accustomed to planning our development infrastructure on the climate data of the past 30–50 years,” he said. “We now need to plan according to anticipated changes."