NEW DELHI: Cloud bursts, such as the one that deluged Mumbai in 2005, could become a more frequent reality. Instead of occurring once in 20 years as they do on an average now, by the end of 21st century, it could happen as often as every five years and cause much greater damage, a yet-to-be released report by UN's Inter-governmental Panel on Climate Change (IPCC), accessed by TOI, says.

Mumbai went through an aqua-shock in July, 2005, after 944 mm of rain fell - half the downpour the city receives annually on an average - within only 24 hours. Poor sanitation and drainage systems, incapable of handling the massive rainwater, had led to floods, crippling India's financial capital and causing an economic loss of $690-$1,890 million. The threat from such aqua shocks could treble by 2070, IPCCwarns if climate change goes unchecked and the city does not adapt.

The flooding could have been managed better, if Mumbai's drainage systems were improved. The report devotes a lot of space to the Mumbai deluge, pointing out that the poorest suffer more in cities and that adaptation work - such as drainage management - too would not cover all the risks with increase in high rain events and rising sea levels - both of which could occur during this century as mercury rises.

The draft IPCC report is more careful than it ever was before the 'Himalayan blunder' controversy tarnished the institution's reputation. Yet, the predictions are dire.

IPCC scientists confidently say that places such as the Sundarbans, which are suffering coastal erosion and inundation, will continue to suffer as sea levels rise.

The global average temperatures will rise by 1-3 degrees Celsius by 2050 and 2-5 degrees Celsius by the end of the century. This may look like an insignificant figure, but its impacts on agriculture and water resources could be dramatic.

"It is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes will occur through the 21st century on the global scale," the report says.

There will be more days with extreme heat and the temperatures on those days will also go higher than what we have witnessed till now.

Given these are predictions, the IPCC is careful to categorize the level of confidence (the probability that something might happen) for each forecast it discusses in the report.

There is worse news for India. Even though the nation had contributed little to the problem of climate change it is among the countries suffering the worst. Developed countries that have emitted most of the accumulated greenhouse gas emissions since industrialization era suffer lesser losses than emerging economies such as India and China, the report says.

"The relative economic burden in terms of direct loss expressed as a percentage of GDP has been substantially higher for developing countries. Middle income countries with rapidly expanding asset bases have borne the largest burden, and during the period from 2001-2006 losses amounted to about 1% of GDP, while this ratio has been less than 0.1% of GDP for high income countries," it says. During the 25-year period (from 1979 to 2004), over 95% of deaths from natural disasters occurred in developing countries, it notes.

This lays bare the irony of the rich nations refusing to provide funds or technologies to developing countries and asking emerging economies to take binding emission cuts even as they shy from their commitments under the Kyoto Protocol.

The IPCC report is likely to undergo changes and could be toned down as government representatives come to a consensus on its findings ahead of its formal release by the end of November.