NOAA reports that 15,272 warm-temperature records were broken. In some places, nighttime temperatures exceeded previous record daytime highs. Average March temperatures were 8.6 degrees F above the 20th century average for the month. Only one month, January 2006, has recorded a greater deviation from average temperatures in the 1,400 months or so of record-keeping.
The warm weather set up conditions for severe thunderstorms. In early March a tornado outbreak swept across the Ohio Valley and the Southeast and became the year’s first disaster to exceed one billion dollars in damages and loss. Hawaii experienced a rare tornado, during which fell the state’s record hailstone, measuring 4½-inches in diameter.
Nationally, overall precipitation was slightly above average. However, the interior West, Northeast and Florida were drier than average, while the Pacific Northwest and the Southern Plains were much wetter. By the end of the month drought conditions in the contiguous United States had lessened slightly, dropping from 38.7 percent to 36.8 percent.
Temperature trends of the first quarter of 2012 culminated in March. The three-month average was 6 degrees F above the long-term average in the continental U.S. However, Alaska experienced its ninth-coolest first quarter, with temperatures 5.2 degrees below average. Average precipitation for January-March was down by 0.29 inches, with several regions of the country experiencing unusually dry winter conditions.
Globally, March’s remarkable warmth spread across most of Canada as well as the contiguous United States, through Mexico, Argentina, Peru and eastern Brazil; across Europe and parts of northern and central Russia; India and China. Cooler-than-average conditions were recorded in Alaska, Australia, eastern and western Russia and parts of New Zealand. While the month was the 16th warmest March since record-keeping began in 1880, globally the average temperature in March was the coolest since 1999. Although the extent of arctic sea ice continues to be below its historic average, it was greater than any measured since 2008.
April continued the pattern of unusual weather, with a late snowstorm hitting the Northeast the week before May.
While many climatologists are reluctant to declare that any single weather event is the direct consequence of global warming, such anomalous weather is consistent with predictions of how warming temperatures will affect climate. As scientists examine such events as the March heat wave, they increasingly comprehend the myriad complex interactions of the planet’s climate system. Recent studies of a decade of severe weather events demonstrate growing evidence that global climate change, the result of greenhouse gas emissions, is driving the unusually frequent and intense disasters.