Assicuratori preoccupati per gli effetti del cambiamento climatico, danni sempre più ingenti da catastrofi naturali

From floods that crippled countries, to mega cyclones, huge blizzards, killer tornadoes to famine-inducing droughts, 2011 has been another record-breaker for bad weather.

While it is too early to predict what 2012 will be like, insurers and weather prediction agencies point to a clear trend: the world’s weather is becoming more extreme and more costly.

Following are details of major weather disasters for 2011 and some early forecasts for 2012.

Global reinsurer Munich Re says natural catastrophe losses for the first nine months of 2011 totaled $310 billion, a record, with 80 percent of all economic losses occurring in the Asia-Pacific region. Since 1980, weather-related disasters globally have more than tripled.

The United States set a record with 12 separate billion-dollar weather disasters in 2011, with an aggregate damage total of approximately $52 billion, the National Oceanic and Atmospheric Administration said this month.

The U.N.’s World Meteorological Organization said global temperatures in 2011 are currently the 10th highest on record, higher than any previous year with a La Niña event, which has a relative cooling influence.

The 13 warmest years have all occurred in the 15 years since 1997. The extent of Arctic sea ice in 2011 was the second lowest on record, and its volume was the lowest.

Scientists say a warming atmosphere and more moisture in the air are providing fuel for weather systems, leading to more extremes. Rising levels of greenhouse gases from industry, transport and deforestation are providing that extra heat.

January — Record floods swamp Australia’s east coast, killing 35 people, shutting coal mines, wiping out roads, rail lines and thousands of homes and costing more than $2 billion in insured losses.

– “Snowmageddon”: Heavy snows blanket large parts of the United States including record falls in New York.

February — Cyclone Yasi, one of the largest and most powerful storms ever to hit Australia, strikes northern Queensland State, devastating sugar and banana crops.

– Massive winter storm hits U.S. Midwest and Northeast, causing travel chaos and power outages.

April – Series of tornadoes batter U.S. Southeast, killing an estimated 364 people.

May – Tornado hits U.S. town of Joplin, killing about 160 people, the single deadliest U.S. twister since 1947.

– Floods in U.S. Midwest and Mississippi River Valley inundate millions of acres, trimming corn and soy plantings.

June – Floods in China’s central and southern provinces kill more than 100 people. More than half a million are evacuated.

July – Worst drought in decades in the Horn of Africa triggers famine in Somalia and leaves 13 million people at risk starvation in a crisis expected to last well into 2012.

– Flooding between July and late November in Thailand kills more than 600, affects a third of the country, causes damage of at least $42 billion and inundates nearly 1,000 factories near Bangkok, disrupting auto and electronics global supply chains.

August – Hurricane Irene kills at least 40 people in the eastern United States and triggers the worst flooding in decades in some states. Economic losses estimated to top $10 billion.

September – Scores die in worst flooding along the Mekong River since 2000.

October – Rare October snowstorm kills 13 in U.S. northeast and leaves 1.6 million without power.

December – Tropical storm Washi hits the Philippine island of Mindanao, triggering flash floods and mudslides and killing more than 1,200 people.

– Year-long drought in U.S. state of Texas causes more than $5 billion in agricultural losses and triggers wildfires that burn 4 million acres (1.6 million hectares). Summer temperatures in Texas break U.S. records.

A La Niña event in the Pacific Ocean is expected to last well into 2012. The phenomenon is a cooling of waters in the central Pacific and has a global impact on weather.

Forecasters expect it to bring above-average rains to northern and eastern Australia and more cyclones than normal during the Australian November-April storm season. La Niña events also tend to strengthen the Atlantic hurricane season.

Colorado State University researchers expect an above-average hurricane season if conditions that bring warmer than usual tropical water temperatures in the Atlantic continue and there are no major El Nino events.

El Nino is a warming of surface waters in the eastern and central Pacific, affecting wind patterns that can trigger droughts in Australia and suppress Atlantic hurricanes.

Winter across Europe and the United States is also expected to be milder, forecasters say.

“The common thread this winter compared to last is the presence of La Niña,” said Chris Vaccaro, public affairs director, at the National Weather Service in Washington. “But the La Niña we have now and through the winter is not anticipated to be as strong as last year.”

In addition, the Arctic Oscillation, which was negative last year and sent frigid air southward leading to huge snowstorms, has largely been positive this year. The oscillation is a shift in atmospheric pressure cells that changes wind patterns.

A negative phase triggers high pressure over the Arctic and low pressure at mid-latitudes, which makes the Arctic zone relatively warm, but spills cold Arctic air southward to places like the U.S. Midwest and Northeast.

Most of continental Europe, the Nordic region and Britain will see warmer-than-normal weather between January and March, Weather Services International (WSI) said last week.

(Sources: Reuters, NOAA, WMO, Colorado State University) (Additional reporting by Nina Chestney in London and Timothy Gardner in Washington; Writing by David Fogarty; Editing by Ron Popeski)