Global warming 'has had a role' in making 2012 the hottest ever recorded in the lower 48 states, says a US climatologist. The average temperature was 54.3 degrees F., a full degree higher than the previous annual record.
The year 2012 was the warmest on record for the continental United States, eclipsing 1998's record average temperature of 54.3 degrees by a full degree Fahrenheit.
While one degree's difference may not seem like much, the spread between the record coldest year, 1917, and the previous record warm year, 1998, is just 4.2 degrees F. With 2012's record-high reading, the gap has grown by 25 percent, according to preliminary data from the National Climatic Data Center (NCDC) in Asheville, N.C.
Last year marked the 15th consecutive year of above-normal average annual temperatures for the continental US.
Global warming "has had a role in this," says Jake Crouch, a climatologist at the NCDC, during a briefing Tuesday on the year's data. Annual average temperatures for the lower 48 states have been increasing over the past century, although he noted that it's difficult to know how much of the warming in 2012 could be pegged to human-induced climate change versus natural variability.
Regionally, the Northeast, Southwest, South, and North West Central US posted record high annual temperatures, with the North West Central US coming in at 3.9 degrees F. above the long-term average, followed by the Northeast at 3.4 degrees F. above the long-term average.
Beyond temperatures, the continental US posted the second worst year, after 1998, for severe weather, as measured by the NCDC's US Climate Extremes Index.
The most pervasive severe conditions in 2012 centered on the ongoing drought in the US. At one point in July, moderate to exceptional drought, as measured by a gauge known as the Palmer Drought Severity index, covered 61 percent of the US. Other measures still put the drought coverage at 61 percent of the country, covering most of the western two-thirds of the US.