So far this year, twisters in the United States have killed nearly 100 people and caused hundreds of millions of dollars in wind damage.

The first recorded tornado ripped through downtown Atlanta on March 14. Earlier this month, at least 40 tornadoes leveled hundreds of homes and killed 24 people in states including Georgia, Missouri and Oklahoma.

With thousands dead from the cyclone in Myanmar and memories still fresh from the wave of hurricanes leading up to Katrina in 2005, anxiety is mounting about extreme weather and raising questions about whether it is tied to global warming.

But, so far, science shows no clear links between the recent twisters and climate change.

More likely, the tornadoes are the result of the age-old Pacific phenomenon known as La Niña.

It sends warm air currents earlier in the year at parts of the so-called Tornado Alley of the South, Midwest, and Great Plains, unleashing twisters sooner in a season that generally runs from late winter through midsummer.

The fact that their destruction has been particularly visible this year, scientists say, has more to do with location--these twisters passed through populated areas -- rather than a surge in the number of storms that occur overall.

This year "part of it is bad luck," said Harold Brooks, a research meteorologist at the federal government's National Severe Storms Laboratory, in Norman, Okla.

There have been "slightly more strong tornadoes," he adds, "interacting with a lot more people."

Though 2008 will go down as an above-average year for tornadoes, meteorologists said, it is unlikely to approach the devastation of 1925, when one deadly March twister -- dubbed the "Tri-State Tornado" -- swept through Missouri, Illinois and Indiana, contributing 695 deaths to a full-year toll that reached 794.

Preliminary studies suggest as many as 774 twisters in the U.S. so far this year, though that number is expected to decrease as scientists consolidate multiple sightings and dismiss other misleading data.

By mid-May 1998, one of the most recent precocious tornado seasons, 411 tornados had occurred.

Tornado statistics have much to do with where the storms occur.

Because of their rapid development and formation close to the ground, many go unseen by radar and satellites, which can identify broader rotational patterns that create tornadoes but not the twisters themselves.

Eyewitness reports are vital to confirm actual funnel clouds.

A study published in April by Mike Brown and Adam Thomas, two meteorologists at Mississippi State University, found a direct link between population density and the number of tornadoes that are reported.

"Many weak tornados are likely not reported in … areas of low population density simply due to a lack of observation," they concluded.

Also fueling awareness these days is the growing number of "storm watchers" across the country who help meteorologists identify tornadoes and other server storms.

Equipped with cell phones, wireless Internet connections and sprawling online communities dedicated to severe weather phenomena, amateur meteorologists and other volunteers increasingly help track twisters that once would have gone unseen

Skywarn, a network of volunteer storm watchers who help the National Weather Service spot severe storms, now boasts about 280,000 members compared with about 80,000 a decade ago.

"A lot more people are out there watching than there were in the past," said Mike Gibson, a Suwanee, Ga., software developer whose program, GR2 Analyst, has become popular with meteorologists, broadcasters and hobbyists because it renders three-dimensional reproductions of actual tornadoes from data complied by weather radars.

Images of mobile homes torn off their foundations and wooden houses rent not splinters point to a need for stricter building codes, safety experts say apart from traditional building techniques and materials.

While building codes have become stricter in coastal areas pummeled by hurricanes, codes haven't been as strictly enforced further inland, where tornadoes can generate winds exceeding 300 miles an hour.