March high temperatures that broke century-old records were in part fueled by global warming from human activity, an early analysis from the National Oceanic and Atmospheric Administration said.

In a draft report dated April 3 from NOAA’s Earth System Research Laboratory Physical Sciences Division, federal scientists examining Upper Midwest and Ohio Valley Region conditions estimated that human-caused global warming “contributed on the order of 5% to 10% of the magnitude of the heat wave during 12-23 March.”

The report, which contemplates predicting similar events in the future, added that there is an increased “probability” of heat waves as global warming progresses.

The hottest March on record has set off a debate among meteorologists about contributing factors. Some cite the weather phenomenon La Nina. One factor for the March highs was the position of the jet stream. Typically, it takes a flatter line from west to east. But in March, the jet stream dipped far south and rose north to the Great Lakes bringing in masses of hot air from the Mexican and U.S. deserts, Mike Pigott, senior meteorologist with AccuWeather, said.

“It was a spectacularly warm March across the Plains, Midwest and East,” Pigott said. “It is a cause for concern if you look back over the years, there have been a large number of record warm temperatures set, rather than record cold events. The numbers are skewed toward record high temperatures.”

The NOAA report added that there can always be “random events.” It does contain qualifications due to the complexity of the task.

The draft noted that it is “an evolving research assessment and not a final report.” It doesn’t “represent official positions” of federal agencies including NOAA. A telephone call to the author of the report was not immediately returned Monday.

In a separate report released Monday, NOAA said that March weather highlights included 223 preliminary tornado reports in a month that averages 80 tornadoes. The majority of tornadoes occurred during the March 2-3 outbreak across the Ohio Valley and Southeast, which killed 40 and caused damage exceeding $1.5 billion, NOAA said.

Record and near-record breaking temperatures dominated the eastern two-thirds of the nation and contributed to the warmest March on record for the lower 48 states, a record dating to 1895, NOAA said.

The average temperature of 51.1 degrees was 8.6 degrees above the 20th century average for March and .5 degrees warmer than the previous warmest March in 1910.