"We saw extraordinary land, sea surface temperatures, extraordinary ocean heat accompanied by very extreme weather affecting many countries around the world, destroying lives, livelihoods, hopes and dreams," WMO spokesperson Clare Nullis said. "We saw many climate change impacts retreating sea ice glaciers. It was an extraordinary year."

Four of the six international datasets crunched by WMO indicated a higher than 1.5℃ global average increase for the whole of last year but two did not.

The 1.5℃ marker is significant because it was a key goal of the 2015 Paris Agreement to try to ensure that global temperature change does not rise more than this above pre-industrial levels, while striving to hold the overall increase to well below 2℃.

Climate deal under pressure

The Paris Agreement is "not yet dead but in grave danger", the WMO maintained, explaining that the accord's long-term temperature goals are measured over decades, rather than individual years.

However, WMO Secretary-General Celeste Saulo insisted that "climate history is playing out before our eyes. We've had not just one or two record-breaking years, but a full ten-year series. "It is essential to recognize that every fraction of a degree of warming matters. Whether it is at a level below or above 1.5C of warming, every additional increment of global warming increases the impacts on our lives, economies and our planet."

LA fires: climate change factor

Amid still raging deadly wildfires in Los Angeles that weather experts including the WMO insist have been exacerbated by climate change - with more days of dry, warm, windy weather on top of rains which boosted vegetation growth - the UN agency said that 2024 capped a decade-long "extraordinary streak of record-breaking temperatures".

UN Secretary-General António Guterres described the WMO's findings as further proof of global warming and urged all governments to deliver new national climate action plans this year to limit long-term global temperature rise to 1.5C - and support the most vulnerable deal with devastating climate impacts.

"Individual years pushing past the 1.5℃ limit do not mean the long-term goal is shot," Mr. Guterres said. "It means we need to fight even harder to get on track. Blazing temperatures in 2024 require trail-blazing climate action in 2025," he said. "There's still time to avoid the worst of climate catastrophe. But leaders must act - now."

The datasets used by WMO are from the European Center for Medium Range Weather Forecasts (ECMWF), the Japan Meteorological Agency, NASA, the US National Oceanic and Atmospheric Administration (NOAA), the UK Met Office in collaboration with the Climatic Research Unit at the University of East Anglia (HadCRUT) and Berkeley Earth.

Listen back to an interview climate scientist Alvaro Silva at the WMO, following the heat alert in the United States at the end of June:

Ocean warming

Highlighting a separate scientific study on ocean warming, WMO said that it had played a key role in last year's record high temperatures.

"The ocean is the warmest it has ever been as recorded by humans, not only at the surface but also for the upper 2,000 metres," the UN agency said, citing the findings of the international study spanning seven countries and published in the journal Advances in Atmospheric Sciences.

WMO noted that about 90 per cent of the excess heat from global warming is stored in the ocean, "making ocean heat content a critical indicator of climate change".

To put the study's findings into perspective, it explained that from 2023 to 2024, the upper 2,000 metres of ocean became warmer by 16 zettajoules (1,021 Joules), which is about 140 times the world's total electricity output.