Four key climate change indicators broke records in 2021: UN

Four key climate change indicators — greenhouse gas emissions, sea level rise, ocean heat and ocean acidification — broke worldwide records in 2021, the United Nations weather agency announced on Wednesday.

Extreme weather, which the World Meteorological Organization (WMO) described as “the day-to-day face of climate change,” resulted in hundreds of billions of dollars in economic losses last year. Such conditions also took a heavy toll on human lives — rattling global food and water security and causing displacement, the WMO found in its State of the Global Climate in 2021 report.

“Today’s State of the Climate report is a dismal litany of humanity’s failure to tackle climate disruption,” Secretary-General António Guterres said in a video message on Wednesday morning.

“The global energy system is broken and bringing us ever closer to climate catastrophe,” he added.

Guterres described fossil fuels as “a dead end,” stressing that the ongoing war in Ukraine and its effects on energy prices provide “yet another wake-up call” that “the only sustainable future is a renewable one.”

He called upon nations across the world to act in this decade to stymie the worsening impacts of climate change and keep global warming below 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.

Greenhouse gas concentrations climbed to a global high in 2020 — to 149 percent of pre-industrial levels — and continued to rise in 2021 and early 2022, according to the WMO report.

The global annual mean temperature in 2021 reached about 1.11 degrees Celsius above the 1850-1900 pre-industrial average, less warm than in some recent years due to the cooling effects of La Niña weather conditions at the beginning and end of the year.

Nonetheless, the past seven years collectively were the seven warmest years on record, the authors noted.

Ocean heat levels reached record highs in 2021 and were expected to continue warming in the future — a shift that the report authors described as “irreversible on centennial to millennial time scales.”

Ocean acidification, which threatens marine organisms and ecosystem services, also broke records in 2021, according to the report. The ocean absorbs about 23 percent of annual human-generated carbon dioxide emissions — causing a reaction with seawater that leads to acidification, authors explained.

As the ocean becomes more acidic and its pH decreases, the capacity of seawater to absorb carbon dioxide from the atmosphere also plunges, according to the report. Open ocean surface pH has dropped to “the lowest it has been for at least 26,000 years,” the authors noted, citing the U.N.’s Intergovernmental Panel on Climate Change.

Global mean sea level climbed to new highs in 2021, after surging an average of 4.5 millimeters per year over the 2013-2021 period, according to the report.

This was more than double the rate of the 1993-2002 period and was mainly the result of loss of ice mass from the world’s ice sheets, the authors found. Such losses could have serious consequences for hundreds of millions of coastal residents and increase vulnerability to cyclones.

“Our climate is changing before our eyes,” WMO Secretary-General Petteri Taalas said in a statement.

“The heat trapped by human-induced greenhouse gases will warm the planet for many generations to come,” he continued, stressing that such impacts will persist means to remove carbon from the atmosphere are invented.

“Some glaciers have reached the point of no return and this will have long-term repercussions in a world in which more than 2 billion people already experience water stress,” Taalas added.

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