2016 was second-warmest year on record for continental United States

While 2012's heat record still stands, the breadth of near-record heat across the continental United States is unprecedented.

After months of broken heat records across the globe, the National Oceanic and Atmospheric Association (NOAA) has declared 2016 the second-hottest year on record in the continental United States.

The data, collected by NOAA's National Centers For Environmental Information (NCEI), indicated that the average temperature for the Lower 48 was 54.9 degrees F. (12.7 degrees Celsius) last year. The only other year where that average was higher was in 2012, when the average temperature clocked in at 55.3 degrees F. (12.9 degrees Celsius).

The NCEI data indicates that global climate change has become more easily measurable on a local level over the last few years. While scientists have known about rising global temperatures for decades, most of the immediate changes for areas like the United States have been subtle compared with changes in areas like the Arctic. But in recent years, the overall trend of warming has become more obvious, even when accounting for fluctuations in ordinary weather patterns.

According to the NCEI report, each state experienced average temperatures in 2016 within the top seven hottest ever recorded. Of those, all but Iowa, Maine, Nevada, Oregon, and Utah found 2016 in the top five hottest years on record. While only Georgia and Alaska actually hit record temperatures this year, the number of states close to breaking their heat records was characterized by NOAA as "unparalleled in the nation's climate history."

"The fact that the US has seen the two warmest years (2012 and 2016) within the past five years cannot be explained by chance," Pennsylvania State University climate scientist Michael Mann told the Associated Press. "It bears the fingerprint of human-caused climate change." 

The year 2016 marks the 20th consecutive year that the average temperature of the Lower 48 states surpassed the 20th-century average temperature; The last below-average temperature measured in 1996. The report also found that average rainfall in the continental US was 31.7 inches, 1.76 inches above average rainfall levels over the last century.

"We are seeing bigger doses of rain in smaller amounts of time," Deke Arndt, climate monitoring chief at NOAA's National Centers for Environmental Information in Asheville, N.C., told the Associated Press.

These large doses of rain drove four flooding events in Texas, Louisiana, and West Virginia that collectively cost the country $15 billion in damage. Despite the floods, drought areas in the Lower 48 states increased in 2016 from 18.4 percent to 22.5 percent, though the actual average drought area for the year was at its lowest since 2010.

Last year marked the continuation of a particularly warm streak for Alaska, which saw its third consecutive hottest year on record. That state has seen temperatures rise by an average of 0.3 degrees F. per decade since 1925, twice the average rate of increase for the continental US.

"[The NCEI report] is certainly a data point on a trend that we've seen: a general warming," said Arndt. "All five of the warmest years on record have been since 1998 in the US."

Global temperatures will be calculated later this month, but many experts and organizations have already predicted that 2016 will go on the books the planet's hottest year on record, including the World Meteorological Organization last November. The previous hottest year was 2015.

This article contains material from the Associated Press.

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