Four critical climate change indicators broke records in 2021, the United Nations (UN) said on Wednesday, as it warned humanity of an impending catastrophe driven by the unsustainable global energy system.

According to the ‘State of the Global Climate in 2021’ report by the UN’s World Meteorological Organization (WMO), the previous year saw record high greenhouse gas concentrations and sea level rises, while ocean acidification, ocean heat, and global average temperatures also hit record levels.

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Here are some of the key takeaways from the report:

1) Greenhouse gas concentrations:

Greenhouse gas concentrations in the world hit a new high in 2020, but continued to rise through 2021, reaching 419.05 ppm in April 2021, and 420.23 ppm in April 2022, the highest-ever concentration of carbon dioxide in human history. The last time carbon dioxide concentration was consistently above the 400 ppm mark was 4 million years ago.

2) Ocean acidification:

Oceans absorb approximately 23% of anthropogenic carbon dioxide emissions annually and the absorbed carbon dioxide reacts with seawater to raise ocean acidification. In other words, as the pH levels of oceans decrease, their ability absorb carbon dioxide also decreases.

In 2021, the pH level of the open ocean surface hit its lowest level in 26,000 years, and the UN warned that current rates of ocean acidification are at its highest in nearly 25 millennia.

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3) Ocean heat:

The report also revealed that the upper 2000 metres of oceans also reached record high temperatures in 2021, a trend that is expected to continue strongly in the decades to come, courtesy of human activity.

4) Sea level rise:

Helped the accelerated loss of ice mass from icesheets in the Antarctic and the Arctic, the global mean sea level hit a record high in 2021, after increasing a record pace of 4.5mm annually from 2013 to 2021, double the rate of average sea level rise recorded between 1993 and 2002.

5) Global average temperatures:

Additionally, the alarming rise in global average temperatures continued, with the global mean temperature in 2021 being 1.11 ±0.13 °C above pre-industrial levels. While 2021 was relatively cooler than the previous years thanks to the cooling effect of La Nina, 2015 to 2021 remain the seven hottest years on record.

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A dire warning:

Commenting on the findings of the UN report, Secretary-General Antonio Guterres slammed global efforts to combat climate change, calling the report a “a dismal litany of humanity’s failure to tackle climate disruption.”

“The global energy system is broken and bringing us ever closer to climate catastrophe,” the 73-year-old added.

WMO chief Petteri Taalas also reiterated the existential threat posed by climate change, which has been overshadowed by the ongoing war in Ukraine, warning, that climate change “is still the biggest challenge we are having as mankind.”