* Cyclones to get stronger, dump more rain
* Crops at risk but new varieties can curb losses
* Miners to rethink how to operate faced with more severe storms
By David Fogarty, Climate Change Correspondent, Asia
SINGAPORE, Feb 10 (Reuters) - Witnesses to Cyclone Yasi's destructive tear across northeastern Australia described it as a monster for its size and ferocity. It was also an omen.
Climate scientists say global warming is heating up the world's oceans and atmosphere, providing more fuel for tropical cyclones and creating ever greater risks for crops, miners and billion-dollar beachfronts.
The risks from stronger storms flow right through the heart of the global economy, affecting food security and inflation, iron ore and coal production and higher insurance losses.
Particularly vulnerable are Asia's booming coastal megacities from Manila to Karachi, large areas of the U.S. Gulf and east coast, Australia's iron-ore and northern coal mines and tropical Asia's rice-growing river deltas.
Insurers say unrelenting development along coastlines is placing more homes, businesses and infrastructure in the path of destruction that will drive up insurance losses.
United Nations data says 231 million people lived in cities in Asia in 1950. By 2050, that figure is forecast to grow to more than 3 billion.
Climate change and stronger storms are also a growing threat to Asia's rice crop.
Asia grows 90 percent of the world's rice and the International Rice Research Institute in the Philippines estimates an additional 8 to 10 million tonnes of rice needs to be produced each year, meaning disruption from droughts, floods and storms can hurt supplies and cause price spikes.
Munich Re said there were 950 natural catastrophes recorded last year, 90 percent of which were weather-related events such as storms and floods, making it the year with the second-highest number of natural catastrophes since 1980.
A major climate study in 2010 based on the results of a range of computer models concluded there was likely to be a substantial increase in the number of storms in the severe category range of 3 to 5, with 5 being the maximum.
Overall, storms would be between 2 and 11 percent more intense by 2100 and rainfall would increase about 20 percent near the centre, it predicted.
The study also found that, with the exception of the Atlantic, there might be a drop in the number of storms in the Pacific and around Australia, but the storms that did form would tend to be more dangerous.
"Since the early 1990s, we have seen a significant increase in the number of hurricanes in the Atlantic," said Peter Hoeppe of reinsurer Munich Re, pointing to a natural cycle in which hurricane numbers vary over several decades.
"We think now we have a mixture of two phenomena, one is the natural oscillation and the other is the steady increase in sea surface temperatures due to global warming. And this adds up to increased risks," said Hoeppe, head of Geo Risk Research and Munich Re's Climate Centre.
Hurricane Katrina, Rita and Wilma in 2005 highlighted that risk, as did Hurricane Andrew that struck Florida in 1992. According to the U.S. National Hurricane Center, Katrina killed 1,500 people and caused $81 billion in damage while Andrew caused $26.5 billion in losses, not adjusted for inflation.
In Asia, there was a danger in assuming nothing needs to be done if storm numbers don't increase, said climate scientist Johnny Chan, one of the authors of the 2010 review.
"It is a grim picture. Even if the number of storms is not increasing, the amount of rain that comes out of these storms is increasing," said Chan, director of the Guy Carpenter Asia-Pacific Climate Impact Centre at City University of Hong Kong.
Fellow climate scientist John McBride said there was little doubt storms would become stronger as seas warm. Oceans soak up much of the excess heat and carbon dioxide caused by burning fossil fuels and the oceans have already warmed on average about 0.5 degrees Celsius.
"You should expect a shift towards more intense cyclones. That's coming across as a stronger prediction," said McBride, of the Centre for Australian Weather and Climate Research.
In 2009, typhoons Ketsana and Parma caused damage and losses to crops, property and infrastructure of $4.4 billion in the Philippines, or 2.7 percent of gross domestic product, the World Bank says. For the year, storms led to the loss of 1.3 million tonnes of rice paddy, forcing the country to import.
A year later, Typhoon Megi, a maximum category 5 storm, killed 26 people in the Philippines and caused rice crop losses of more than 520,000 tonnes.
Tropical Asia's vast river deltas are also at risk from flooding and powerful storm surges from cyclones.
Cyclone Nargis, which ripped through the Irrawaddy Delta in Myanmar in 2008, killed or left missing 140,000 people and triggered a 2.5 metre (8 ft) storm surge that inundated much of the delta, wiping out a third of the rice crop.
Reiner Wassmann, IRRI's co-ordinator of climate change research, said new varieties of rice that were flood and saltwater tolerant would help reduce losses from storms. Faster-growing varieties could also help farmers avoid the typhoon season.
Australia's A$2 billion sugarcane crop is particularly vulnerable to more powerful storms. Floods over the past several months caused losses of A$500 million, said Steve Greenwood, chief executive of Queensland's Canegrowers Association.
Cyclone Yasi, a large category 5 storm, caused further losses of up to a quarter of the remaining crop.
But Greenwood said while there was little farmers could do faced with 250 km/h (156 mph) winds that smash cane stems, new varieties could at least reduce losses from flooding.
Hoeppe of Munich Re expected insurance losses to rise, in part because of greater risks to mines, such as Australia's storm-prone northern open-pit iron ore and coal mines that are central to global steel production.
Australia is the world's top iron ore exporter and also a top thermal and coking coal producer.
Climate change was already prompting major miners to re-assess the weather risks to their operations and existing designs of infrastructure, such as road, rail and port links and holding capacity of tailings dams, analysts say.
The key to existing strict building codes is the assessment of the return period of extreme weather events. That assessment is now being challenged. Munich Re says weather related natural catastrophes have tripled in the past 30 years in Australia.
"I think what people are still coming to grips with is how the traditional civil engineering design guidelines around return periods. Those are going to change," said Peter Lilly, a senior minerals and energy strategist at Curtin University in Perth, Western Australia.
"The historical 1 in 100, 1 in 200 and 1 in 500 years events are going to change. The traditional design criteria are going to have to change," he said. (Additional reporting by James Regan, Rebekah Kebede and Bruce Hextall in Australia; Editing by Alex Richardson)