Measured continuously since 1980 on Amsterdam Island, the average monthly concentration of carbon dioxide (CO2) has reached a new high of 420 ppm (parts per million).
Atmospheric concentrations of carbon dioxide (CO2) and methane (CH4) have been monitored continuously at Amsterdam Island in the Indian Ocean since 1980 (CO2) and 2004 (CH4). The average monthly concentration of CO2 has reached a new high of 420 ppm (parts per million), 24% higher than the first measurements taken in 1980. The annual growth rate has also reached an all-time high, with an increase of +3.7 ppm between April 2023 and April 2024, reflecting the increasing rate of CO2 growth in the atmosphere.
The previous highest value for the CO2 growth rate was observed between July 2015 and July 2016 (+3.6 ppm/yr). What these two peaks have in common is that they follow El Niño episodes, a climatic phenomenon that causes a rise in global temperatures and fuels numerous extreme events around the world. These climatic disturbances affect CO2 exchanges with the oceans and terrestrial ecosystems (droughts, fires, etc.), and result in a temporary acceleration in CO2 growth. The excess CO2 associated with El Nino events is superimposed on the man-made emissions responsible for the increase in CO2 concentrations observed everywhere, including in very remote observatories such as Amsterdam Island and Reunion Island.
The continuing growth in the world’s consumption of fossil fuels is leading to an acceleration in the growth of CO2 atmospheric concentrations, which can be seen very clearly in our observatories monitoring the atmospheric composition.
The methane (CH4) concentration measured over the last 20 years on Amsterdam Island is also rising, and now exceeds 1850 ppb (parts per billion). As with CO2, the rate of increase in CH4 shows variations from one year to the next, superimposed on a long-term upward trend. Unlike CO2, the last few months have seen moderate growth in methane (less than 5 ppb/year), whereas it reached record levels, in excess of 15 ppb/year, between 2020 and 2022. The acceleration in CH4 growth in recent years appears to be attributable to a number of causes, including significant emissions from tropical wetlands, and an increase in the lifetime of methane linked to the drop in nitrogen oxide emissions during the 2020 confinements associated to the COVID pandemic.
Long-term observation programmes for greenhouse gases are essential to our understanding of the increase in these gases in response to human activities and climate disturbances that affect the natural fluxes of CO2 and CH4. The record rise in CO2 observed in our observatories illustrates how far we still have to go to stabilise the radiative forcing generated by the use of fossil fuels
