Not one, not two or three, but four alarm bells have just been sounded by the UN on climate change.

Through the voice of the World Meteorological Organization (WMO), which publishes this Wednesday its "State of the global climate in 2021", the international organization highlights the records broken by four key markers of climate change: the concentrations of gases at greenhouse effect, sea level rise, temperature and ocean acidification.

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

“The global energy system is broken and bringing us closer and closer to climate catastrophe,” he warns, urging to “end fossil fuel pollution and accelerate the transition to renewable energy before incinerating our only home.

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Within 0.4 degrees of the Paris agreement

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

Even despite the La Nina weather phenomenon, which had a chilling effect on global temperatures at the start and end of the year, 2021 remains one of the hottest years on record, with an average global temperature of around 1, 11 degrees Celsius above the pre-industrial level.

As a reminder, the 2015 Paris climate agreement aims to limit global warming to +1.5°C compared to the pre-industrial era.

"Our climate is changing before our eyes," said WMO chief Petteri Taalas.

“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.

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Records broken

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

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, the report said.

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 caps", underlines the document.

Ocean temperature also hit a record high last year, surpassing the 2020 value, according to the report.

The combination of these four key indicators “builds a cohesive picture of a warming world that affects all parts of the planet,” the report says.

And these different markers could be mutually reinforcing.

Thus, the ocean absorbs around 23% of the annual CO2 emissions of human origin in the atmosphere.

Although this slows the increase in atmospheric CO2 concentrations, the latter reacts with seawater and leads to ocean acidification.

“Renewable energy transformation can be the peace project of the 21st century”

As the heat penetrates ever deeper, the top 2,000 meters of the ocean will also continue to warm, "an irreversible change on time scales of centuries to millennia" according to the WMO.

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.

“If we act together, the transformation of renewable energy can be the peace project of the 21st century,” he said.

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