The world is facing a critical challenge as the rise in atmospheric carbon dioxide levels continues to outpace global climate targets. According to the latest forecast from Met Office scientists, the rate of atmospheric CO₂ increase this year will remain too fast to meet the climate goals outlined for limiting global warming to 1.5°C. This is despite a temporary small slowdown associated with natural climate fluctuations.
The annual average CO₂ concentration at the Mauna Loa Observatory, in Hawaii, is projected to rise by 2.37 ± 0.55 parts per million (ppm) in 2026 compared to 2025, reaching a new high of 429.4 ± 0.6 ppm. This alarming trend is primarily driven by human-caused emissions from fossil fuel burning and deforestation, with natural carbon sinks only providing a temporary respite.
Professor Richard Betts, who leads the production of the forecast, explains, "The slight slowdown in the rate of CO₂ increase is only attributed to a temporary strengthening of natural carbon sinks – such as areas of tropical forest which draw down carbon dioxide- thanks to moderate La Niña conditions observed in late 2025 and early 2026. These conditions promote increased CO₂ absorption by plants and oceans, but the overall trend remains upward, with concentrations continuing to climb well above the trajectories required to cap global warming at 1.5°C compared with the period 1850-1900."
The Keeling Curve record of atmospheric levels of carbon dioxide at Mauna Loa has been maintained by the Scripps Institution for Oceanography, University of California San Diego since 1958. This record reveals an accelerating rise in atmospheric CO₂, primarily driven by human activities. While natural carbon sinks have removed a substantial amount of CO₂ from the atmosphere, concentrations have surged by over 50% since the industrial revolution. In the absence of these natural processes, the increase would have been nearly double.
The largest observed annual CO₂ rise on record so far was between 2023 and 2024, surpassing forecasts. This unexpected increase highlighted the complexity of atmospheric CO₂ dynamics and the influence of factors beyond direct emissions, including climate variability and unaccounted natural processes. Recent CO₂ increments at Mauna Loa significantly exceed those projected in scenarios compatible with limiting warming to 1.5°C, as outlined by the Intergovernmental Panel on Climate Change (IPCC).
The Paris Agreement requires a rapid slowdown and eventual cessation and reversal of the CO₂ rise, yet the current and forecasted rates remain well above these critical benchmarks. For the first half of the 2020s, the average annual rise observed at Mauna Loa was 2.61 ppm, in contrast to the 1.33–1.79 ppm per year required by the IPCC's most ambitious scenarios. While the forecast rate of CO₂ increase is incompatible with the 1.5°C goal, every fraction of a degree of avoided warming matters as it reduces the risks and impacts to people and nature. It is crucial to minimize the exceedance of 1.5°C global warming as much as possible.
