The National Oceanic and Atmospheric Administration (NOAA) reported that global carbon dioxide levels hit a record high in 2023. This surge puts us in a hazardous position, resembling atmospheric circumstances from the Pliocene epoch, around 4.3 million years ago.
The Pliocene epoch witnessed significant environmental change. While not as hot as other times in Earth’s history, global temperatures were several degrees higher than now, and sea levels were much higher. These variations were most likely caused by natural fluctuations in Earth’s orbit and tilt, but the current spike is caused by human activities.
This was the twelfth consecutive year in which carbon dioxide levels increased by more than 2 ppm
During that geological period, sea levels were about 23 meters higher than they are today, and the average temperature was 7 degrees Fahrenheit warmer than it was in pre-industrial times.
The global surface CO2 concentration in 2023 was 419.3 parts per million (ppm), up 2.8 ppm from 2022.
This was the twelfth consecutive year in which carbon dioxide levels increased by more than 2 ppm. According to NOAA monitoring records, this pattern began in 2014. Furthermore, atmospheric CO2 levels in 2023 were more than 50% greater than in the pre-industrial era.
“The 2023 increase was the third-largest in the last decade and is likely a result of an ongoing increase of fossil fuel carbon dioxide emissions, coupled with increased fire emissions, possibly as a result of the transition from La Nina to El Nino,” Xin Lan, a Cooperative Institute for Research in Environmental Sciences scientist, said in a statement.
Methane levels in the atmosphere are now more than 160 percent greater than they were during the pre-industrial period
Another greenhouse gas detected in the NOAA analysis was methane, which was at record-high levels. Despite its lower abundance than CO2, it is more effective at trapping heat in the atmosphere.
Methane levels rose to an average of 1922.6 parts per billion (ppb), a 10.9 ppb increase over 2022. Methane levels in the atmosphere are now more than 160 percent greater than they were during the pre-industrial period.
The single-year increase in 2023, however, is lower than the yearly growth rates observed in 2020 (15.2 ppb), 2021 (18 ppb), and 2022 (13.2 ppb).
The year 2023 was the seventh highest since 2007. Methane levels first increased in the 1980s. It practically plateaued in the early 2000s until significantly growing again in 2007.
Nitrous oxide, the third most major human-caused greenhouse gas, increased by 1 ppb to 336.7 ppb in 2023
According to a 2022 study and additional NOAA research in 2023, increased microbial emissions from livestock, agriculture, human and agricultural waste, wetlands, and other aquatic sources accounted for more than 85 percent of the rise between 2006 and 2021. The remainder could be derived from fossil fuel emissions.
“In addition to the record high methane growth in 2020–2022, we also observed sharp changes in the isotope composition of the methane that indicate an even more dominant role of microbial emission increase,” said Lan, adding that the exact causes of the recent surge are yet unknown.
The researchers now intend to investigate if climate change is driving wetlands to emit methane in a loop in reaction to warming.
Nitrous oxide, the third most major human-caused greenhouse gas, increased by 1 ppb to 336.7 ppb in 2023. This growth in recent decades can be traced back to the use of nitrogen fertilizer and manure as agriculture expanded and intensified. Nitrous oxide concentrations are 25% greater than their pre-industrial level of 270 ppb.