A mild winter, an early spring and warmer-than-average temperatures every season have contributed to a record-breaking year, as 2015 will go down as the warmest in Oregon since state records began in 1895. Oregon’s previous record high average temperature of 49.9 degrees was set in 1934 – the height of the Dust Bowl – when the entire country was plagued by hot, dry weather.
Despite a cold, icy end to December in Oregon, the average temperature in 2015 was 50.4 degrees, not only a record but far above the average yearly temperature for the 20th century, which was 47.8 degrees, according to Oregon State University’s Philip Mote, who directs the Oregon Climate Change Research Institute on campus.
“In previous years, we’ve had periods where the weather was warmer for differing spells,” Mote said. “In 2015, though, it was warmer than average almost all the way through the year.” A combination of meteorological conditions and greenhouse gases led to the record warm year, he added. The statistics are from the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.
Oregon was not alone in experiencing a warm 2015, according to Kathie Dello, deputy director of the Oregon Climate Service at OSU. Washington, Montana and Florida also experienced record high temperatures, and in several other states 2015 went down in the top five of all time. It appears this will be yet another record warm year for average global temperature, Dello pointed out, and it is officially the second warmest year in the United States, despite blizzards and Arctic temperatures in the Northeast.
“If you are 31 years of age, you have not lived through a single month in which the global temperature was below average,” Dello said. “And if you are 31 and living in Oregon, you have only experienced three years here that were cooler than the 20th-century average.” Researchers calculate the average temperature for each day by looking at the highest and lowest temperatures. If the high reaches 90 degrees and the low is 60, that day’s average temperature is 75 degrees. They then calculate the average monthly temperature, and finally, the average yearly temperature.
The average for the state is done by analyzing temperatures at a series of long-established weather stations throughout the state. “We had a ridge of high pressure that set up and kept the weather warm and dry throughout most of the summer and fall,” Mote said. “That followed a winter in which we got nearly average precipitation, but much of it came from the south and it fell as rain instead of snow.”
Mote said the record-setting 2015 weather was a combination of meteorological phenomena and the Earth gradually getting warmer because of human activities. Through rigorous statistical analysis, scientists are able to tease out the impacts of El Niño, greenhouse gas emissions, volcanic activity and solar activity on temperatures. Mote said 2015 would have been a warm year because of meteorological conditions, but the 1-2 degrees (F) attributable to greenhouse gases pushed temperatures into record territory.
“There’s little doubt that the insulation of the planet from greenhouse gas emissions played a role in the warming throughout the year,” he said. The OSU researchers say expect more of the same in 2016. “With El Niño and the remnants of The Blob (a huge warm patch of water in the North Pacific Ocean), it should be another warm year for the Earth, and for Oregon,” Dello said.
Information and photos by OSU