Yesterday, a dozen tornadoes ripped through Dallas, spurring panic in a highly populated, 6 million-strong metropolitan area. The footage captured by news helicopters was dramatic—semi trucks and trees were hurled into the air like newspapers tossed from a malevolent paperboy.
But the fleet of Texan tornadoes only marks the latest in a year that has already been packed with extreme weather—we've had record-hot winter months, unusually early tornadoes in the midwest, and states wracked with drought. Here's a closer look.
There was nothing tremendously out of the ordinary about the tornadoes that hit Dallas, but climatologists were concerned about the spate of twisters that swept through Kentucky, Indiana, and three other states in early March. Those tornadoes killed 39 people and exacted untold property damage to homes and buildings across the region.
And tornado season doesn't usually begin until April, leading climate scientists to link the warmer weather to earlier (and potentially longer) seasons. Here's Joe Romm:
The unexpectedly fierce and fast tornado outbreak so early in the season has folks asking again about a possible link to climate change. Climatologist Dr. Kevin Trenberth emailed me that, because of climate change, “there is every expectation that the [tornado] season will move up in time. The warm winter in the US is perhaps an indicator of the nature of the changes to be expected.”
Trenberth also elaborates on the link between tornadoes and climate change in a recently published paper, which notes that "Global warming does not contribute directly to tornadoes themselves, but it does contribute to the vigor of the thunderstorms that host them through the increased warmth and moisture content (moist static energy) of the low level air flow." Meaning: there's no evidence tornadoes themselves are more powerful, but the storms from which they come will be. Which is one reason climatologists speculate that the 2011 tornado season broke records in terms of casualties—539 were killed by 1070+ tornadoes.
The 2011-12 winter has become the "winter that wasn't" in common parlance, and for good reason. Climatologists have confirmed that it was the fourth warmest winter season on record. Furthermore, for much of the nation, March was the hottest ever—25 cities and regions broke heat records last month.
Reuters reported that "Last month was the warmest March on record across half of the United States with summer-like temperatures." And "Accuweather.com said cities in more than 25 states, as well Washington, D.C., broke records for average daily temperatures last month, including Chicago, Oklahoma City, Des Moines, Milwaukee, Indianapolis and Detroit."
Statisticians and meteorologists point out that we're breaking many more heat records than cold ones—which is useful evidence that global warming is continuing an ascendent trajectory.
Drought was a major story in 2011, especially in Texas, where the majority of the state was parched for most of the year. Well, that drought stretched on into 2012, too. And though the state was met with a brief reprieve with some scattered rainfall in late February, drought conditions stretched on through March. 70% of the state was listed as experiencing "severe drought", and 14% suffered from "exceptional" drought.
But it's not just Texas. Colorado too has entered an unusual drought—according to the Denver Post, a startling "98 percent of the state is experiencing varying levels of drought."
Wendy Ryan, a research associate at the Colorado Climate Center, told the Post that "In Fort Collins, we had the hottest and driest March on record ... This is the first time we've ever had only a trace of precipitation for March. No years have had zero."
And now for the inevitable disclaimer: No single specific weather event can be said to be caused by global climate change. But scientists are anything but hesitant to explain that the kinds of phenomena described above are symptomatic of global warming—these are the kinds of things we'll expect to see more of in a warming world. And the combined weight of each; of the hottest-ever record temperatures that continue to be broken, of the increasingly ornery storm systems, of the unprecedented dry seasons, all help drive home on a visceral level what the scientists have been telling us for decades now.
Human activity is causing the world to warm. Warmer temperatures means the air holds more moisture, so: Wet areas will get wetter. More rain, more storms. Where there's little moisture to be found in the first place, the hot, dry regions will become hotter—and drier. The extremes are exacerbated; that's the calling card of global climate change.
For a useful final word, here's Dr. Trenberth: "The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be…"