Approximately 1,000 tornadoes. Nearly 500 dead. The numbers are staggering as the 2011 tornado season rages at a record pace. From the the EF5 tornado that struck Joplin, Mo., killing at least 122 people to become the deadliest tornado in the U.S. since 1950, to the pair of explosive and deadly April tornado outbreaks, and now also yesterday’s Plains outbreak moving east today, this year’s barrage of violent twisters has people asking questions about everything from the impact of climate change on tornadoes, to the accuracy and effectiveness of short-term severe weather warnings.

Given the sheer volume of the tornado chatter, the online equivalent to a twister’s whipping winds, it’s useful to take a step back and review the important questions that need to be asked at this point, while reminding ourselves of what is generally known.

Climate change connection?

First, on the “are all these tornadoes a manifestation of global warming?” question, there is a consensus on that, but it’s neither comforting nor conclusive. We simply don’t know.

As I wrote last month, climate change is expected to change key ingredients needed for tornado formation (for example, the amount of water vapor in the atmosphere worldwide is already on the rise, and this can contribute to greater atmospheric instability), but there hasn’t been any trend in observational data to suggest that tornado behavior – either frequency, strength, or regions they typically strike – is shifting. Tornadoes are extremely capricious events, and teasing out statistically significant trends from historical records is very difficult.

High-resolution radar image of a tornado south of Oklahoma City yesterday. (Twitpic from Brad Panovich, WCNC-TV (@wxbrad))

Climate scientists have already demonstrated trends in other extreme weather and climate events, including floods and heat waves, showing that manmade climate change is tilting the odds in favor of their occurrence. However, such research is lacking when it comes to tornadoes, with computer modeling studies suggesting that conditions may become more favorable for tornadoes as the climate warms, but perhaps not by very much.

Jeff Masters at Weather Underground discussed yesterday the causes of this year’s high tornado count and summarized his thoughts with the following:

“In summary, this year’s incredibly violent tornado season is not part of a trend. It is either a fluke, the start of a new trend, or an early warning symptom that the climate is growing unstable and is transitioning to a new, higher energy state with the potential to create unprecedented weather and climate events. All are reasonable explanations, but we don’t have a long enough history of good tornado data to judge which is most likely to be correct.”

So while the jury is out on the relationship between climate change and tornadoes, there is one factor that has clearly played a major role in this year’s high tornado death toll: Bad luck. Sure, the more tornadoes there are the better chance that one or more will eventually tear through a highly populated area. But just think, had a tornado in southwest Missouri Sunday evening tracked just a few miles further north or south – well, a lot fewer of us would know where to find Joplin on a map right now.

Killer tornadoes trumping technology, warning system

Next, this tornado season has obliterated the notion that massive investment in a national severe weather forecasting infrastructure and early-warning network ensures a low tornado death toll. When this devastating tornado season finally ends, the meteorology community, along with emergency planners and social scientists, need to explore how it is that despite a network of Doppler radars, National Weather Service forecast offices, tornado sirens, live TV coverage and social media alerts, we still lost so many people.

As Russell Schneider, the director of NOAA’s Storm Prediction Center, told the Associated Press:

”I think we have to ask ourselves the tough questions now.”

”Why is this happening? The complexity of our society, the density of our populations in traditional tornado-prone regions of the world, community and family preparedness? Our science and technology -- are we fully exploiting that to protect Americans?”

Masters made a keen observation when he put the human toll into historical perspective (bold emphasis added): “The first tornado warning wasn’t issued until 1948, and virtually all tornadoes from the 1950s and earlier hit with no warning. On average, tornado deaths in the United States decreased from 8 per 1 million people in 1925 to 0.12 per 1 million people in 2000. Had this year’s tornadoes occurred 50 years ago, I expect the death toll would have exceeded three thousand.

Among tornado researchers, it’s widely recognized that population growth and the increasing urban sprawl is a driving factor that is placing more people in harm’s way. I gave a presentation to the American Meteorological Society several years ago on the challenge of dealing with urban tornadoes, and this issue has only grown in urgency since.

There are unique aspects of getting the word out about severe weather in cities that don’t necessarily apply in rural areas of “Tornado Alley.” Disseminating tornado warnings in urban areas can be especially difficult, since people are often tuned into different forms of media, and may not be reachable by tornado sirens, if they are even available. Forecasters are increasingly turning to new media — and social media platforms in particular — to spread tornado warnings. For example, Twitter can be a very effective system for pushing severe warnings to an affected area. Here at the Capital Weather Gang we’ve been increasingly turning to Twitter (@capitalweather and @dcweatheralerts to disseminate alerts for significant and severe weather.

Aerial view of Joplin tornado damage via FEMA director Craig Fugate’s Twitter feed (@CraigatFEMA).

Also relevant is the growth of the portion of Americans who live in mobile homes, which are particularly susceptible to strong winds, be they from tornadoes, hurricanes, or typical severe thunderstorms. According to the AP, citing U.S. Census records, seven percent of Americans – about 20 million people – now live in mobile homes. Also, the greatest share of mobile homes is in the South, where tornado deaths have been especially significant this year.

But making sure that people get the warnings is only half the battle. You also have to get people to take appropriate action once they get the warning, and considering that tornado warnings have a high false alarm rate (as high as 75 percent, by some estimates), people can be forgiven for being skeptical that a given warning will turn out to be the real deal.

Already some are discussing “tornado fatigue” and the ability of the human psyche to distance itself from existential threats, thereby leading people to avoid heeding tornado warnings that could be false alarms (a similar dynamic comes into play concerning climate change, but that involves a longer-term threat).

As Jeffrey Kluger wrote for,

“…paradoxically, what may be the true undoing of good tornado preparedness is the sheer number of the storms themselves. When twisters are touching down by the dozens per day (a whopping 68 were reported in the Midwest this past weekend), being more rather than less prepared would seem the way to go. But familiarity breeds habituation, and habituation, in turn, breeds insouciance. Of the many reasons the Department of Homeland Security recently scrapped its much-mocked color-coded terrorism alert system, one of the greatest was the arbitrary — and often politically cynical — way it was overused. The first time the alert went from yellow to orange, Americans jumped out of their skins. The 51st time, they simply rolled their eyes.”

The Christian Science Monitor ran an insightful article that provides a thorough overview of some of the insights that social scientists have been providing into how people respond to severe weather warnings.

Certainly some tornadoes have been met with what can most charitably be described as a laissez faire response by officials who should know better, as was the case when a violent tornado barreled toward Lambert-St. Louis International Airport on April 22. Despite 34 minutes of warning, the airport authority didn’t take action until the storm was practically on top of them, too late to make any public announcements about the danger to travelers in the terminal buildings.

However, when you’re dealing with so many violent tornadoes on the scale of EF3 and above, there is a limited array of options for people to pursue in order to ensure their safety. In Tuscaloosa and Joplin, many homes were wiped clean, leaving just their foundations. Thus, anyone not underground was in grave danger. Those kinds of monster tornadoes hitting populated areas are going to kill, no matter how accurate the forecast or how effective the warning system.