320 miles north of the Arctic Circle, a weather station in Americas northernmost city of Utqiavik (formerly Barrow ), Alaska, has been quietly collecting temperature data since the 1920s .

Early this month, while preparing a report on U.S. climate, experts at the National Centers for Environmental Information (NCEI) noticed something odd: They were missing data from Utqiavik for all of 2017, and some of 2016.

It turns out the temperatures recorded at Utqiavik over that time were warmer than had ever seen before. So much so, in fact, that an automated computer system set up to police data and remove irregularities had flagged it as unreal and excluded it from the report.

Heres how Deke Arndt, chief of NOAAs Climate Monitoring Branch, explained the event :

In an ironic exclamation point to swift regional climate change in and near the Arctic, the average temperature observed at the weather station at Utqiavik has now changed so rapidly that it triggered an algorithm designed to detect artificial changes in a stations instrumentation or environment and disqualified itself from the NCEI Alaskan temperature analysis, leaving northern Alaska analyzed a little cooler than it really was.

In his ensuing in-depth breakdown of how something like this could happen, Arndt noted that, over time, things like a weather stations precise location, temperature recording equipment and basic procedures can change, leading to variations in its data.

To account for that, the NCEI has developed an algorithm that helps filter out the noise and alert scientists if something a broken sensor, say needs to be checked out.