Major greenhouse gases continued steady climb in 2023
The three major greenhouse gases - carbon dioxide, methane and nitrous oxide - showed no signs of slowing their long-term steady climb in 2023.
Atmospheric carbon dioxide (CO2) concentration reached 425.38 parts per million in March at the Mauna Loa Observatory in Hawaii. The last time it was that high was 4.3 million years ago when the average global temperature was over 7 degrees F higher than pre-industrial levels and the global average sea level was 75 feet higher than it is today.
Scientists also closely study the growth rate of atmospheric CO2. Unfortunately, we also continue to see decadal increases in CO2 since the 1990s. Last year was also the 12th consecutive year where the atmospheric concentration of CO2 increased by more than 2 ppm.
Methane (CH4) concentrations, which are much more potent but less widespread than CO2, have increased their growth rates in the past 10 years. Agriculture and the melting of permafrost are significant sources.
Methane levels are now more than 160 percent higher than pre-industrial levels.
Finally, global nitrous oxide (N2O) concentrations continue to see a steady climb. The primary sources of nitrous oxide are from fertilizers and manure. N2O also causes a reduction in the ozone layer.
