Average global temperatures at the start of June were the warmest the European Union's climate monitoring unit has ever recorded for the period, trouncing previous records by a "substantial margin", it said on Thursday.

The news comes as the El Nino climate phenomenon has officially arrived, raising fears of extreme weather and more temperature records.

"The world has just experienced its warmest early June on record, following a month of May that was less than 0.1 degrees Celsius cooler than the warmest May on record," said Samantha Burgess, deputy director of the Copernicus Climate Change Service (C3S).

"Global-mean surface air temperatures for the first days of June 2023 were the highest in the ERA5 data record for early June by a substantial margin", said Copernicus. Some of the unit's data goes back as far as 1950.

Copernicus recently announced that global oceans were warmer last month than in any other May on record.

The unit also said that at the beginning of June, global temperatures exceeded pre-industrial levels by more than 1.5C (34.7 degrees Fahrenheit), which is the most ambitious cap for global warming in the 2015 Paris Agreement.

According to the data, the daily global average temperature was at or above the 1.5C threshold between June 7-11, reaching a maximum of 1.69C above it on June 9.

While it is the first time the cap has been breached in June, this limit has been exceeded several times in winter and spring in recent years.

"Every single fraction of a degree matters to avoid even more severe consequences of the climate crisis", Burgess said.

Copernicus is based in the Germany city Bonn, where UN-led climate talks are taking place ahead of the COP28 climate summit scheduled to take place in Dubai at the end of the year.