The World Meteorological Organization, the specialised agency of the United Nations monitoring weather and climatic conditions, has confirmed that last year was the fourth hottest year on record.

The WMO also confirmed that taken together, the past four years were the four warmest years on record.

According to the UN agency, the average global temperature last year was 1 degree Celsius above pre-industrial levels.

The hottest year was 2016, when average temperatures of 1.2 degrees above historic levels were recorded.

The confirmation from the WMO came just ahead of the publication of the latest update on global climate conditions from NASA and the National Oceanic and Atmospheric Administration.

Secretary General of the WMO, Petteri Taalas, also confirmed that 20 of the warmest years on record have all occurred in the past 22 years.

However, he said: "Temperatures are only part of the story. Extreme and high impact weather affected many countries and millions of people, with devastating repercussions for economies and ecosystems in 2018.

"Greenhouse gas emission reduction and climate adaptation measures should be a top global priority."

Australia has just had its warmest January on record, with heatwaves unprecedented in their scale and duration.

Tasmania had its driest January on record, conditions that brought destructive bushfires.

The WMO said today that intense heatwaves are becoming more frequent as a result of climate change.

Extreme heat in the southern hemisphere contrasted with extreme cold in parts of North America in January.

The WMO Secretary General pointed out that the Arctic is warming at twice the global average.

A large fraction of the ice in the region has melted, and those changes are affecting weather patterns outside the Arctic in the Northern Hemisphere.

A part of the cold anomalies at lower latitudes could be linked to the dramatic changes in the Arctic, he said.

He added that what happens at the poles does not stay at the poles, but influences weather and climate conditions in lower latitudes where hundreds of millions of people live.