The World Meteorological Organization (WMO) has issued a sobering report: atmospheric levels of heat-trapping carbon dioxide (CO2) surged to unprecedented highs last year. This marks the largest single-year increase since modern monitoring began in 1957, irrevocably committing our planet to a future of higher temperatures.
The alarming rise is attributed to a combination of persistent human-caused emissions, a growing number of devastating wildfires, and a concerning reduction in CO2 absorption by natural ‘sinks.’ These crucial natural systems, including forests and oceans, became less effective at sequestering carbon in 2024, a year that also happened to be the warmest on record.
CO2 growth rates have dramatically tripled since the 1960s, escalating from an average annual increase of 0.8 parts per million (ppm) to 2.4 ppm between 2011 and 2020. More recently, from 2023 to 2024, the global average concentration of CO2 leaped by 3.5 ppm – the most significant annual jump to date. Over the last two decades, average CO2 levels have climbed from 377.1 ppm in 2004 to a staggering 423.9 ppm in 2024, far exceeding the recognized safe threshold of 350 ppm.
The WMO bulletin also highlights record concentrations of methane and nitrous oxide, the second and third most significant long-lived greenhouse gases linked to human activities.
Ko Barrett, WMO deputy secretary-general, emphasized the urgency: “The heat trapped by CO2 and other greenhouse gases is supercharging our climate, leading to more extreme weather events. Reducing these emissions is vital not only for our climate but also for our economic stability and the well-being of our communities.”
This authoritative scientific information on greenhouse gas concentrations is a critical warning for negotiators from over 190 countries. As they prepare to convene for the annual UN climate change conference in Belem, Brazil, this November, the bulletin serves as a stark reminder to accelerate climate action.
Normally, about half of the total CO2 emitted each year is absorbed by Earth’s land ecosystems and oceans. However, this natural storage capacity isn’t permanent. As global temperatures climb, oceans become less efficient at absorbing CO2 due to decreased solubility. Simultaneously, land-based carbon sinks are negatively impacted by various factors, including the increasing frequency and severity of droughts.
Oksana Tarasova, a senior scientific officer at WMO, voiced a growing concern: “There is apprehension that both terrestrial and ocean CO2 sinks are becoming less effective. This trend will inevitably lead to more CO2 remaining in the atmosphere, thereby accelerating global warming.”
In 2024, the global average methane concentration reached 1942 parts per billion (ppb), representing a staggering 166% increase above pre-industrial levels (before 1750). Nitrous oxide levels also hit a record high of 338 ppb in 2024, a 25% increase over pre-industrial levels.
Nitrous oxide, the third most important long-lived greenhouse gas, originates from both natural sources and human activities like biomass burning, fertilizer use, and industrial processes. Methane, which contributes approximately 16% to the warming effect of long-lived greenhouse gases and has a lifespan of about nine years, is 40% from natural sources and 60% from anthropogenic activities such as cattle farming, rice cultivation, fossil fuel exploitation, landfills, and biomass burning.