Levels of heat-trapping greenhouse gases in the atmosphere that are causing the Earth to grow hotter at an ever-alarming pace reached a new record last year and there is no relief in sight, the U.N. weather agency said in a new report prepared for the upcoming COP28 climate summit.
Researchers at the World Meteorological Organization said on Wednesday they have recorded increased levels in all three of the primary gases that contribute to global warming: carbon dioxide, methane and nitrous oxide.
"The abundance of heat-trapping greenhouse gases in the atmosphere once again reached a new record last year and there is no end in sight to the rising trend," WMO said.
In its latest Greenhouse Gas Bulletin, the Geneva-based WMO said globally averaged concentrations of carbon dioxide, the most important greenhouse gas, were a full 50% above the pre-industrial era for the first time in 2022, and continued to grow in 2023.
In 2022, CO2 concentrations were at 418 parts per million in the atmosphere, methane at 1,923 parts per billion, and nitrous oxide at 336 parts per billion. These levels account for 150%, 264% and 124%, respectively, of pre-industrial levels – before the Industrial Revolution from 1750 to 1850.
The rate of growth in CO2 concentrations was somewhat less than in 2021 and the average for the decade. But rather than offering a slim glimmer of hope, WMO said this was probably the result of natural, short-term variations in the carbon cycle. In fact, new emissions as a result of industrial activities continued to rise.
Atmospheric CO2 concentrations have risen well beyond the 350 ppm that some scientists and environmental groups promote as the absolute upper limit. By comparison, CO2 concentrations were hovering around 385 ppm at Hawaii's Mauna Loa Observatory ahead of the 2009 U.N. climate talks in Copenhagen, where the world first agreed on a 2° target for warming above pre-industrial levels.
For decades, researchers have been warning of the severe climate disruptions that will occur if concentrations hit around 450 ppm. Some environmentalists have warned the world already passed a danger point at 350 ppm and must go back. The U.N.'s Intergovernmental Panel on Climate Change, hosted by WMO, has detailed how fossil fuel burning leads to more extreme weather, droughts, flooding, loss of plant and animal species, and sea level rise from the melting of land ice.
Heading in the 'wrong direction'
The last time the Earth’s atmosphere held a comparable concentration of heat-trapping CO2 was 3 million to 5 million years ago, when the temperature was 2-3° Celsius warmer and sea level was 10-20 meters (32 to 65 feet) higher than now.
“Despite decades of warnings from the scientific community, thousands of pages of reports and dozens of climate conferences, we are still heading in the wrong direction,” said Petteri Taalas, head of the WMO.
Given the current level of greenhouse gas concentrations, the Earth is on the way to seeing temperatures increase well above the Paris Agreement's upper target of keeping the mean global temperature to below 2° above pre-industrial levels by the end of the century.
“This will be accompanied by more extreme weather, including intense heat and rainfall, ice melt, sea-level rise and ocean heat and acidification,” Taalas said. “The socioeconomic and environmental costs will soar.”
In 2015, the 196 nations signing onto the Paris treaty – which entered into force in Nov. 2016 – committed to hold global warming to no more than 2° Celsius above pre-industrial levels, or preferably 1.5°.
Fossil fuels are the main cause of climate change
Mainly because of our addiction to fossil fuels, along with cement production, carbon dioxide is the single most important greenhouse gas in the atmosphere and accounts for an estimated 64% of global warming.
WMO said the slightly smaller growth in CO2 concentrations last year was likely the result of terrestrial ecosystems and the oceans absorbing more carbon dioxide during several years of a La Niña climate pattern. However, the shift this year to an El Niño event may likewise have unforeseen consequences for greenhouse gas concentrations.
Methane, a potent greenhouse gas that stays in the atmosphere for about a decade, accounts for about 16% of the warming effect of long-lived greenhouse gases. Approximately 40% of methane is emitted into the atmosphere by nature – wetlands and termites, for example – and about 60% comes from human-caused sources like raising farm animals, rice agriculture, fossil fuel exploitation, landfills and biomass burning.
Nitrous oxide is a powerful greenhouse gas as well as an ozone-depleting chemical and accounts for about 7% of the long-lived greenhouse gases. It’s emitted from both natural sources (60%) and human activity (40%) – and its year-on-year increase in 2022 was the highest ever recorded.
Climate costs rising in the U.S.
On Tuesday, the United States released its National Climate Assessment, a report issued every four or five years. The study found that the U.S. is warming about 60% faster than the world as a whole with far-reaching consequences, such as heat waves, drought, flooding rains and wildfires.
U.S. President Joe Biden said the “impacts are only going to get worse, more frequent, more ferocious and more costly.” Climate-related disasters cost the U.S. US$178 billion last year, the president said.
Even if greenhouse gas emissions are cut substantially, the report found, the impacts of climate change will intensify over the next decade.