Temperatures across the United States in 2012 were the warmest on record, according to NOAA's State Of The Climate report.
Last year was 3.2 degrees warmer in the United States than the average for the entire 20th century.
California had its 4th warmest year on record, said David Pierce, climate researcher with Scripps Institution of Oceanography. "The 4th warmest year in a 110-year record is pretty warm," he said.
Widespread drought and a mostly absent winter pushed the average annual U.S. temperature last year up to 55.32 degrees Fahrenheit -- a full degree warmer than the old record set in 1998.
Pierce called the temperature change "extraordinary" and said the weather phenomenon, La Niña, combined with climate change are to blame.
“We’ve had La Niña’s in the past," said Pierce. "In fact, we’ve had bigger ones. But they didn’t have this much of a temperature effect. So the other part of the reason this was a record year was because of climate change caused by humans -– which is greenhouse gasses and particles we put into the atmosphere."
The U.S. last year also had the second most weather extremes on record. There were 11 different disasters that each caused at least $1 billion in damage.
Pierce said San Diego was fortunate to avoid the worst of them, but was most affected by the Southwest drought.
“We’re linked to the broader U.S. weather patterns because we import so much of our water," Pierce explained. "Some of it comes from the Sierra Nevada and some of it comes from the Colorado river basin – we import 85 percent typically of our water. So when there’s dry conditions and very warm temperatures in the southwestern U.S. - that actually effects us in San Diego County."
The drought was the worst since the 1950s and slightly behind the Dust Bowl of the 1930s, meteorologists said. During a drought, the ground is so dry that there's not enough moisture in the soil to evaporate into the atmosphere to cause rainfall, which leads to hotter, drier air.
Pierce said without a La Nina or El Nino currently in play, it’s hard to predict what 2013 holds.
"Because of climate change, because of human effects, the earth is getting warm in general. So you’ve got a predisposition toward warm temperatures, but you still have natural variability on top of that," said Pierce.
NOAA: Significant Climate Events In 2012
- Tropical cyclone activity across the North Atlantic in 2012 as above-average with 19 named storms, ten hurricanes, and one major hurricane (Category 3 or stronger). This is the third consecutive North Atlantic tropical cyclone season with 19 named storms and ties with as the third most active season for the basin. Isaac and Sandy made landfall along the U.S. coast during 2012 causing significant impacts. Isaac brought large storm surge and torrential rains to the Gulf Coast. Sandy caused significant damage to the Northeast, with 8 million homes losing power and 131 fatalities reported.
- The widespread drought conditions of 2012 peaked in July with approximately 61 percent of the country experiencing drought conditions. The footprint of drought during 2012 roughly equaled the drought of the 1950s which peaked at approximately 60 percent. The size of the current drought and the drought of the 1950s are smaller than the drought episodes of the 1930s. The current drought has yet to reach the intensity or duration of the 1950s and 1930s national-scale droughts.
- Wildfire activity during 2012 was above-average with 9.2 million acres burned the third most in the 13-year record. Numerous large and destructive wildfires impacted the western U.S. throughout the year. The Waldo Canyon fire near Colorado Springs, Colorado destroyed nearly 350 homes and was the most destructive fire on record for the state. The Whitewater-Baldy Complex fire charred nearly 300,000 acres and was the largest on record for New Mexico.
- Tornado activity during 2012 was below the 1991-2010 average of approximately 1,200. The year got off to a busy start with large tornado outbreaks in March and April causing significant damage in the Ohio Valley and Central Plains. May and June, typically the most active tornado months of the year, both had less than half of average tornado counts. The final 2012 tornado count will likely be less than 1,000 — the least since 2002.
