A closer look at tree rings is adding to the growing list of evidence that shows unprecedented temperatures measured on Earth over the past year.

The summer of 2023 was the warmest in the Northern Hemisphere extra-tropical regions — from about New Orleans to the North Pole — in the past 2,000 years, according to a study published in Nature on Tuesday.

Land temperatures in this section of the Northern Hemisphere were 2.07 degrees Celsius — or about 3.73 degrees Fahrenheit — higher in the summer of 2023 than instrumental averages between 1850 and 1900, researchers discovered after combining measurements from thousands of meteorological stations to analyze the June-through-August surface air temperatures across the Northern Hemisphere’s extra-tropical region, which include 30 to 90 degrees north, according to the study.

The researchers also spent months taking samples to compare tree ring reconstruction with nine of the longest temperature-sensitive tree chronologies available for the results, Jan Esper, a professor for climatology at Johannes Gutenberg University in Mainz, Germany, and lead author of the study, told reporters during a press briefing on Monday.

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