Adnan Akyüz, North Dakota’s state climatologist and associate professor of climatological practices at the North Dakota State University, has some concerns about a report by the Associated Press that says the state was the only one in the lower 48 that did not warm up since 1984.

“The study has several flaws,” Akyüz says. “Average temperatures for North Dakota vary a great deal with no discernible pattern. The AP science writer used a linear fit that produced the least amount of differences between the observation and the estimation.”

Climatologists use 30-year averaging to compare individual years. It is useful to determine if a given year is above, below or near normal. However, the climatological normal is only updated once a decade.

“Calculating climatological normal temperatures outside the standard averaging period is not common,” Akyüz says. “Our current averaging period is a 30-year window from 1981 to 2010. We will not calculate the data for the next normal averaging period until 2021. If we updated the normal every year, we would have different normals every year, which would make comparisons of departure from normal across the nation very challenging.”

For example, North Dakota’s long-term temperature trend since 1890 is more appropriate than using a short-term trend of a few years.

“The trend of the last 30 years is highly susceptible to the state’s severe annual temperature swings from warm to cold,” Akyüz says. “For example, based on the state’s average temperature, 2012 was the second warmest, while 2013 brought us the 33rd coldest year during the period from 1890 to 2013. We have to be very careful about the analysis we use to interpret data.”

NDSU Agriculture Communication – June 5, 2014