Last month was the warmest October in the northern hemisphere since records began

The US National Oceanic and Atmospheric Administration agency says last month was the warmest October in the northern hemisphere on record.

There is a 99 per cent probability that 2021 will be one of the 10 warmest years since recordings began. Source: AAP

Last month was the warmest October in the northern hemisphere since records began in 1880, according to measurements by a US climate agency.

The average land temperature over the northern hemisphere exceeded that of October 2019, the previous record holder, by 0.11C, the National Oceanic and Atmospheric Administration (NOAA) said on Monday.

Globally, it was the fourth warmest October on record, NOAA said.

The average temperature over land and ocean areas was 0.89C above the 20th century average of 14C.

Only 2015, 2018 and 2019 were warmer globally.

There is a 99 per cent probability that 2021 will be one of the 10 warmest years since recordings began, NOAA added.

At the end of October, the World Meteorological Organisation announced that, according to preliminary measurements, 2021 was probably not quite as hot as the past three years but that the long-term trend of significant warming had not changed.