Monsoon to get longer: Report

NEW DELHI: North India is likely to heat up more than the southern parts of the country while the entire Indian subcontinent may see longer rainy seasons in second half of the century, the UN's climate body has predicted in its latest comprehensive document on climate change.

The conclusion, showing variation in temperature and rainfall in South Asia, is part of the lengthy technical details of the United Nation's Intergovernmental Panel on Climate Change (IPCC) which made its comprehensive report — Climate Change 2013, The Physical Science Basis — public in Stockholm on Monday.

The findings of the report show that the northern part of the continent is likely to witness winter temperatures rise of up to 0.4 to 0.8 degree Celsius during 2016-35 as compared to the 1986-2005 average, 2 to 3 degree Celsius during 2046-65 and up to 3 to 5 degree Celsius by the end of the century (2081-2100), under different scenarios of action to limit greenhouse gas emissions.

Though the UN body's report on region-wise "impact, adaptation and vulnerability" will come out in March next year, the technical details comprising 14 chapters and Atlas of Global and Regional Climate Projections in its annexure carry indications of these changes in South Asia.

Krishna Kumar Kanikicharla, climate scientist at Pune's Indian Institute of Tropical Meteorology and one of the drafting authors of the IPCC report, told TOI there was "growing evidence" of the impact of the climate change on monsoons in South Asia and the tropical cyclone system in the Bay of Bengal.

Kanikicharla, responsible for drafting the chapter comprising details of monsoon systems, said: "There is strong hint that the duration of the rainy season would increase due to early onset of monsoon. The quantum of rainfall will also increase during the later part of this century."

He said though the Indian summer monsoon circulation will weaken, rainfall will increase due to higher atmospheric moisture resulting from a rise in temperatures.

In its projection for South Asia, the technical summary of the report clearly points at "enhanced summer monsoon precipitation and increased rainfall extremes of landfall cyclones on the coasts of the Bay of Bengal and Arabian Sea".

What is the confidence level of these predictions? Prashant Goswami, one of the lead authors of the IPCC report, admitted that these conclusions were based on climatic projections that were not as firm as those made at a global level.

"These uncertainties increase as you go to smaller scale (from global to regional or from regional to sub-regional levels). But one has to have an element of faith in these conclusions which are based on well defined scientific methodology," Goswami, chief scientist at Bangalore's CSIR Centre for Mathematical Modelling and Computer Simulation, told TOI.

The impact of temperature rise and rainfall variations on the region's agriculture that's highly dependent on monsoon, will be considered in the report on impact, adaptation and vulnerability, to be released next year as part of the IPCC's fifth assessment report (AR5).

As far as global temperature is concerned, the summary report said it was likely to rise by 0.3 to 4.8 degrees Celsius by the end of the century. Sea levels, it said, could rise by 26-82 centimetres by the end of the century.

A S Unnikrishnan, chief scientist of the National Institute of Oceanography, Goa, said policymakers would have to rely on the global sea level rise projections to draw up their strategies to deal with the emerging scenarios.

Urat Refleksi