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Data shows September was the warmest in modern temperature monitoring following months of record-breaking anomalies this year.

Nasa has all but declared this year to be the hottest yet recorded, after September narrowly turned out the warmest in modern temperature monitoring.

Last month was 0.91C above the average temperature for that time of year from 1951 to 1980, the benchmark used for measuring rises.

The new findings follow record-breaking monthly anomalies throughout this year, leading the agency to believe that because of the highs reported so far, 2016 will take the crown as warmest in the 136 years of modern data-keeping.

Last month was only just over the previous record, coming in at a razor-thin 0.004C above the previous high for the time of year, reached in September 2014. That tiny margin may be revised in future, as monthly temperature data can be nudged up or down retrospectively as later reports come in. For instance, June 2016 was initially reported as the warmest on record but was subsequently revised downward slightly to the third warmest.

But it makes the trend for the year, and the long-term decadal trends, easier to discern. September’s high temperatures compared with the long-term average means that 11 of the last 12 consecutive months, back to October 2015, have set new records.

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