Temperatures in the United States have reached record levels, making 2012 the hottest year to date.
A year of negligible winter, punishing heat waves, drought, and monster storms, such as Sandy, contributed to the record year in the continguous United States, according to a report released on Tuesday by the National Climatic Data Center.
Temperature differences are ordinarily measured by fractions of degrees, but 2012 was a full degree Fahrenheit hotter than the previous record.
The average annual temperature in the contiguous United States was 13C last year. That was a full degree Fahrenheit higher than the 1998 record, and 3.2F above the 20th century average, the NCDC said.
NCDC scientists described that difference as a "big deal" – one that over time would begin to redefine what was seen as normal weather conditions for America.
The NCDC is due to release its report on global temperatures next week.
"We are well above the pack in terms of all the years we have data for in the US," Jake Crouch, a climate scientist at NCDC in Asheville, North Carolina, told a reporters' conference call. "Last year was an outlier looking at past temperature records for the US, but as we move forward we can expect to see more of the same."
Scientists have consistently said the big rise in temperatures since the tail-end of the 20th century would not have been possible without the warming owing to climate change. With 2012, the 10 warmest years on record have all occurred within the past 15 years. No month has fallen below the global temperature average since February 1985.
Crouch said natural weather variability was also a factor in the 2012 record. However, the trend line was clear. In total, 356 new all-time heat records were set last year, compared to just four new all-time lows.
It was, on several other counts, a year of extremes.
Last year brought weather events from Sandy, believed to have inflicted more than $60-billion damages on New Jersey and New York, to Hurricane Isaac, tornadoes to a brutal drought.
By the time summer was over, more than 99-million Americans – or about a third of the entire population – had sweltered through 10 or more days hotter than 38C, the NCDC said.
Nineteen states broke existing temperature records.
Sixty-one percent of the lower 48 states was enduring drought. The extreme hot and dry conditions – the worst since the 1950s – burned through the corn fields of the midwest and high plains, delivering a shock to food prices.
While drought has faded from public conversation, it has not relaxed its grip over the winter.
Shipping on the Mississippi has slowed because of low river levels. The Great Lakes are nearing historic lows. Farmers in Kansas report winter wheat crop is at risk.
The closing months of the year also remained stubbornly warm, with the third smallest snowfall on record. "We are still seeing impacts from the drought," Crouch said. "It is not over, and I perceive that is going to be a big story moving forward in 2013." – Guardian