Four key markers of climate change broke new records in 2021, the UN said on Wednesday, warning that the global energy system was driving humanity into disaster.

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Greenhouse gas concentrations, sea level rise, temperature and ocean acidification all set new records last year, the World Meteorological Organization (WMO) said in its “ State of the global climate in 2021”.

This report is "a lamentable litany of humanity's failure to fight climate change", denounced the head of the UN, Antonio Guterres.

“The global energy system is broken and brings us closer and closer to climate catastrophe,” Mr. Guterres warned, urging to “end fossil fuel pollution and accelerate the transition to renewable energy before 'cremate our only home.'

The WMO said human activity is causing changes on a planetary scale: on land, in the ocean and in the atmosphere, with harmful and long-lasting ramifications for ecosystems.

In a press conference, the head of the OMM, Petteri Taalas, underlined that the war in Ukraine had eclipsed climate change, which “remains the greatest challenge for humanity”.

The report confirmed that the past seven years were the seven hottest years on record.

La Nina-related weather events in early and late 2021 had a chilling effect on global temperatures last year. But despite this, 2021 remains one of the hottest years on record, with the average global temperature around 1.11 degrees Celsius above pre-industrial levels.

The 2015 Paris Climate Agreement aims to limit global warming to 1.5°C above the pre-industrial era.

“We are now heading for a warming of 2.5 to 3 degrees instead of 1.5,” assured Mr. Taalas.

“Our climate is changing before our eyes”

“Our climate is changing before our eyes,” he noted. “Heat trapped by human-made greenhouse gases will warm the planet for many generations to come. Sea level rise, heat and ocean acidification will continue for hundreds of years unless ways to remove carbon from the atmosphere are invented.”

Greenhouse gas concentrations reached a new global high in 2020, when the concentration of carbon dioxide (CO2) reached 413.2 parts per million worldwide, or 149% of pre-industrial levels.

They continued to rise in 2021 and early 2022. And the lockdowns linked to the Covid-19 pandemic had no impact on greenhouse gas concentrations in the atmosphere, according to Taalas.

Global mean sea level hit a new record high in 2021, after rising an average of 4.5 millimeters per year from 2013 to 2021.

It had shown an average increase of 2.1 mm per year between 1993 and 2002, the increase between the two periods being "mainly due to the accelerated loss of ice mass from the ice sheets", underlines the report.

Ocean temperature also reached a record high last year, surpassing the 2020 value. The top 2,000 meters of ocean depth are expected to continue to warm in the future – “ an irreversible change on time scales of centuries to millennia,” the WMO said.

The ocean absorbs about 23% of annual man-made CO2 emissions into the atmosphere. Although this slows the increase in atmospheric CO2 concentrations, the latter reacts with seawater and leads to ocean acidification.

Meanwhile, the report says the Antarctic ozone hole is “unusually deep and extensive” at 24.8 million square kilometers in 2021, driven by a strong and stable polar vortex.

António Guterres has proposed five actions to kick-start the transition to renewables 'before it's too late': end fossil fuel subsidies, triple investment in renewables, cut red tape, secure supply raw materials for renewable energy technologies and make these technologies - such as battery storage - freely available global public goods.