The concentration of carbon dioxide (CO2) measured at the Izaña Atmospheric Observatory, Tenerife, reached its highest level in May 2025 since measurements began in 1984. The average value recorded was 430,6 parts per million (ppm), surpassing all previous highs and confirming an upward trend that has accelerated particularly in recent years.
This figure not only represents a new record for the observatory's historical series, but also follow the usual dynamics Since the annual peak in CO2 concentrations typically occurs during spring in the Northern Hemisphere, coinciding with the month of May, this value is therefore also considered the annual peak for the season in 2025.
The evolution of CO2: a growing and accelerating trend
The increase in CO2 in the atmosphere is not a recent phenomenon.Since the 2s, the rate of increase has averaged XNUMX ppm per year, although in the last decade this figure has grown to average 2,4 ppm per yearAnalyzing the most recent data, between 2022 and 2023 the annual average rose by 2,3 ppm, while in 2024 the jump was even greater, reaching 3,4 ppm increase.
This change in the growth rate has been attributed mainly to El Niño-Southern Oscillation climate phenomenonWarm phases of El Niño lead to a greater increase in CO2 concentrations, in contrast to the cold phase, La Niña, which is usually associated with more moderate increases. In May 2023, the transition from almost three years of La Niña to an active El Niño phase occurred, which would explain the recent spike detected in Izaña.
The key role of the Izaña Observatory
The Izaña Atmospheric Observatory, located at 2.373 meters above sea level and far from urban areas, is specially designed to measure what is called background concentration of greenhouse gases in the open atmosphere. This privileged location makes its records a valuable reference, as their figures are often highly representative of the global average.
Because of this, the CO2 increases detected in Izaña They serve as an indicator and projection on how concentrations evolve on a global scale. This characteristic has made the station one of the key points for international monitoring of the gases responsible for climate change.
Influence of the seasonal cycle on CO2 levels
One of the aspects that influence the annual variation of CO2 is its seasonal cycleTypically, concentrations peak in spring due to the lower absorption of carbon dioxide during the winter. As the season progresses and photosynthetic activity of plants and vegetation increases, atmospheric CO2 tends to decrease slightly.
When autumn arrives, the trend is reversed, as the decrease in vegetation cover causes greater release of CO2 into the atmosphereThese natural cycles, however, are insufficient to offset the sustained increase resulting from human activities, as the underlying trend remains clearly upward.
